Plant Physiology and Biochemistry

Antimycin A (AA) is widely used as an inhibitor of the mitochondrial respiratory chain, targeting the Qi site of cytochrome bc1 (complex III). In photosynthetic organisms, AA is also well known to inhibit the photosynthetic PROTON GRADIENT REGULATION 5 (PGR5)-dependent cyclic electron flow around photosystem I (CEF-PSI). Although AA is frequently used as a specific inhibitor of PGR5-dependent CEF-PSI in photosynthetic reactions, we recently clarified that some of the major components of AA, which is typically a mixture of closely related compounds, also exert direct inhibitory effects on photosystem II (PSII). Nevertheless, the binding site and binding mode of AA in PSII remain largely unexplored. Structurally, AA consists of a salicylic acid moiety connected via an amide bond to a hydrophobic dilactone ring moiety. To identify important structural factors of AA for exhibiting inhibitory effects on PSII (assessed by QA- reoxidation measurements), we here investigated the relationship between structure and inhibitory potency using 38 AA-like compounds (AALCs), including commercial compounds and a series of synthetic AA analogs. Some AALCs exhibited substantially stronger impacts on PSII than natural AA. High acidity of the phenolic OH and the presence of a free amide NH of the salicylamide moiety were critical for the effects on PSII. In contrast, while the dilactone ring moiety also affected the inhibitory activity, this was replaceable with certain hydrophobic structures. Based on our results, together with the known structure-activity relationship and binding mode of AA in complex III, we propose tentative binding models for AA in PSII. HighlightsO_LIStructure-activity relationship of AA-like compounds on PSII is examined C_LIO_LISeveral AA-like compounds more potent than AA against PSII are identified C_LIO_LIPhenolic OH acidity and free amide NH of salicylamide moiety are key for AA effects C_LIO_LIThe dilactone ring moiety is replaceable with certain hydrophobic structures C_LIO_LITentative binding models for AA in PSII are proposed C_LI

Blue light using Flavin (BLUF) proteins are microbial photoreceptors that are involved in various physiological responses. Their occurrence and biochemical properties in fungi remain poorly understood. Here, we investigated a putative BLUF photoreceptor from the corn-smut fungus Mycosarcoma maydis (MmBLUF). Domain analysis, multiple sequence alignment of BLUF core regions, and structural modelling indicated conserved canonical BLUF fold and flavin-pocket residues. However, when heterologously expressed, UV-visible and fluorescence spectroscopy revealed different spectral behaviour than canonical BLUF protein. Further, we tested the role of extended N-terminus in modulation of chromophore binding by expressing N-terminus truncated protein variants. Our results suggest that the unusual spectral behaviour is not linked to the truncation construct (extended N-terminus), which also showed similar spectral features, indicating that the extended N-terminus is unlikely to account for an unusual photodynamics characteristics. Our findings support MmBLUF as a structurally conserved putative fungal BLUF-like photoreceptor with different photochemical properties. Further studies are required to establish its chromophore identity, photocycle and function of this unusual BLUF-like domain from fungal system.

Apple scar skin disease (ASSD), caused by Apple scar skin viroid (ASSVd), is characterized by peel scarring, cracking, dappling, and fruit deformation, resulting in reduced fruit quality and marketability. Despite its economic importance, the physicochemical and metabolic alterations underlying disease progression remain poorly understood. To address this knowledge gap, apple fruits representing four stages of ASSD (healthy, lightly infected, moderately infected, and highly infected) were comprehensively characterized. ASSVd infection was confirmed by RT-PCR, amplicon sequencing, and phylogenetic analysis. Fruit morphology and quality attributes, including firmness, total soluble solids (TSS), pH, titratable acidity (TA), and total phenolic content (TPC), were evaluated. ASSVd infection significantly reduced fruit weight and firmness and altered TSS and TA, indicating progressive deterioration of fruit quality. To investigate the underlying metabolic changes, peel and pulp tissues were analysed separately using gas chromatography-mass spectrometry (GC-MS), while major soluble sugars were quantified by 1H nuclear magnetic resonance (1H NMR) spectroscopy. Integrated metabolomic analyses revealed distinct tissue-specific metabolic reprogramming during disease progression. Major soluble sugars declined significantly during early infection, followed by tissue-dependent recovery at later stages, whereas organic acids, amino acids, phenolics, lipids, polyols, and pentacyclic triterpenoids exhibited dynamic stage-dependent changes. Notably, lupeol accumulated progressively, whereas ursolic acid and oleanolic acid declined, indicating disease-associated alterations in host triterpenoid metabolism. Multivariate analyses demonstrated clear metabolic separation among disease stages. Lupeol, ursolic acid, and chlorogenic acid were identified as candidate discriminatory metabolites in the peel, whereas myo-inositol, chlorogenic acid, and aspartic acid were identified in the pulp. Collectively, these findings demonstrate that ASSD induces coordinated, tissue-specific physicochemical and metabolic reprogramming that compromises postharvest fruit quality and reshapes defence-associated metabolism. This study provides the first integrated metabolomic characterization of ASSD progression and identifies potential metabolic biomarkers for disease diagnosis and severity assessment. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=142 SRC="FIGDIR/small/741181v1_ufig1.gif" ALT="Figure 1"> View larger version (56K): org.highwire.dtl.DTLVardef@92e453org.highwire.dtl.DTLVardef@1cc2436org.highwire.dtl.DTLVardef@15d7e27org.highwire.dtl.DTLVardef@1056568_HPS_FORMAT_FIGEXP M_FIG C_FIG

Tomato production, yield and fruit quality face major challenges due to several factors, including the complex polygenic inheritance of agronomically relevant traits, biotic and abiotic stresses, and increasingly stringent regulations limiting the use of phytosanitary products. In this context, bioinoculants have emerged as a sustainable strategy capable of enhancing yield without compromising fruit quality, conferring protection against different stresses and exerting a minimal or no impact on environment and human health. In this study, we evaluated the effects and the underlying mechanisms by which Streptomyces sp. N2A, an actinobacteria isolated from soybean rhizosphere, promotes seed germination, vegetative growth and yield in tomato, without modifying fruit quality. The obtained results demonstrated that the bacterial treatment significantly improved seedlin[g]s emergence and growth and development in vegetative stage. At harvest, yield was also significantly enhanced, mainly driven by increased individual fruit weight, which was positively correlated with a thicker pericarp in fruits from N2A-treated plants. Transcriptional analysis during fruit development revealed a coordinated induction of auxin and cytokinin signaling pathways before and after anthesis, providing a hormonal framework that underlies the promotion of pericarp growth. This study provides evidence of the beneficial effect of inoculation with Streptomyces sp. N2A on tomato yield and constitutes the first report describing the modification of fruit morphology and expression of genes involved in phytohormonal modulation during early growth and development, induced by a plant growth-promoting Streptomyces.

O_LIPlants continuously adjust photosynthesis to balance growth and photoprotection under changing environmental conditions. Environmental fluctuations frequently impose a mismatch between energy production and CO2 assimilation. How photochemical reactions are regulated to maintain performance under these conditions remains a central question in plant biology. C_LIO_LIWe previously developed transplastomic tobacco (Fd1-OE plants) overexpressing ferredoxin (Fd) displaying enhanced photoprotection and growth penalties with a variegated leaf phenotype under greenhouse conditions. Here, we investigate how these plants respond to different growth irradiances using physiological, ultrastructural, and photosynthetic analyses, including PAM, gas exchange, and P700 absorbance measurements, and dynamic-light assays. C_LIO_LIFd1-OE plants progressively recovered growth, leaf phenotype and photosynthetic performance as growth irradiance increased, reaching near WT performance at 1400 mol m-{superscript 2} s-{superscript 1}. This enhanced adaptation to "high-light" was associated with a larger fraction of open PSII reaction centers and enhanced NPQ. Dynamic-light analyses further revealed faster plastoquinone (PQ) turnover, a more oxidized PQ pool and enhanced electron withdrawal downstream of PSI. C_LIO_LIOur results indicate that Fd overexpression redefines the balance between photochemistry and photoprotection. This adjustment shifts adaptation toward higher irradiance and enhances photosynthetic performance under changing light environments. Electron partitioning downstream of PSI emerges as a promising target to improve photosynthetic resilience. C_LI One sentence summaryOverexpression of Fd1 in tobacco plants adjusts photosynthesis/photoprotection trade off to enhance high-light adaptation

The ability of seeds to survive until dormancy recedes and the germination requirements are met is an adaptive strategy. Proteomics improves our understanding of the mechanisms that control the adaptation to environmental heterogeneity. In this study, we investigated two European beech populations from different habitats that differed in dormancy and germination traits. We found that the populations exhibited different germination strategies, which were reflected in coordinated but quantitatively different proteomic reprogramming. The Miekinia population exhibited stronger accumulation of proteins involved in nucleotide sugar biosynthesis, S-adenosylmethionine metabolism, and flavonoid biosynthesis. Enhanced nucleotide sugar biosynthesis indicates more intensive cell wall remodelling and carbohydrate metabolism, which support embryo growth and faster germination. Increased S-adenosylmethionine metabolism suggests the epigenetic and hormonal regulation of germination differences between populations. Higher flavonoid biosynthesis indicates an enhanced antioxidant capacity associated with environmental protection. In contrast, the Wisa population showed stronger accumulation of proteins involved in RNA processing, suggesting tighter post-transcriptional regulation and proteome reorganization during germination. Consistent with its deeper dormancy and later germination, the Wisa population appears to rely more on RNA-level regulation, whereas the Miekinia population prioritizes metabolic activation. These contrasting proteomic profiles likely reflect population-specific physiological strategies associated with dormancy depth and adaptation to different climatic conditions. HighlightProteomic reprogramming reveals population-specific germination strategies in European beech, linking dormancy depth with contrasting metabolic activation and RNA-level regulation during the transition from dormancy to germination.

O_LIC4 photosynthesis and the crassulacean acid metabolism (CAM) rarely co-evolved in a single lineage, but Portulaca can switch from C4 to CAM under drought stress. Little is known about CAM responses to nutrient availability, hence the goal of this work was to assess the influence of macronutrients over C4-CAM. C_LIO_LIP. oleracea was grown hydroponically and subjected to treatments (+/- PEG) for: nitrate deficiency (-NO3-), ammonium (NH4+), NO3- + NH4+, magnesium (-Mg), phosphorus (-P), calcium (-Ca), potassium (-K), and sulphur (-S) deficiencies, and salt stress. Samples were monitored for diurnal titratable acidity ({Delta}H+), osmotic potential, and gene relative expression for core C4/CAM and signaling genes. C_LIO_LI-NO3- induced CAM even without PEG, a process probably without the mediation of abscisic acid (ABA). Notably, -P showed a trend to induce CAM without PEG and -Ca prevented CAM induction even with PEG. Salt stress induced CAM, and NH4+ was not toxic for P. oleracea. Other treatments showed less conspicuous responses. C_LIO_LIThis work brings an unprecedented overview of the nutrition of C4 and CAM, suggesting perspectives for deepening the study of C4-CAM. Understanding the molecular mechanisms and environmental signaling of C4-CAM is essential for realizing the evolution of two CCMs in a single plant. C_LI

Utricularia gibba L. is an aquatic carnivorous plant with a diverse set of capabilities. Reddening of traps frequently occurs in old in vitro cultures. While anthocyanins are often responsible for red coloration in plants, not every plant turns red. Stress factors like high light or excess sucrose have previously been shown to induce the formation of anthocyanins. Here, we hypothesized the red trap formation to be dependent on nutrient deprivation and tested nitrogen deprivation. The results suggest, that only in combination with light, nitrogen deficiency leads to the activation of the complete anthocyanin biosynthesis pathway and visible red coloration. However, in darkness, anthocyanin biosynthesis appears generally less active compared to light conditions and expression of most anthocyanin biosynthesis genes is not significantly upregulated under nitrogen deficiency.

BackgroundSorbus sibirica Dong Hong is a promising ornamental cultivar, but its optimal light conditions remain unclear. AimsThis study evaluated the effects of shading on seedling growth, physiology, root morphology, and leaf surface micromorphology. MethodsOne-year-old seedlings were grown under full sunlight (CK) and 30%, 50%, or 70% shade for 100 days. Growth, biomass, root traits, chlorophyll, invertase, soluble protein, stomatal characteristics, and epicuticular wax morphology were determined. ResultsShading significantly affected all measured traits. The 30% shade treatment produced the greatest seedling height, which increased by 118.18% compared with CK, and the highest chlorophyll content, which increased by 120.21%. Soluble protein content was slightly increased, whereas invertase activity decreased under moderate shading. Although total biomass decreased by 18.63%, root development remained relatively stable under 30% shade, with slight increases in total root length and average root diameter. Stomatal density was highest under this treatment, and the epicuticular wax structure remained relatively regular. In contrast, 70% shade markedly inhibited biomass accumulation and root development. ConclusionsModerate shading, particularly 30%, provided the most favorable light environment for Sorbus sibirica Dong Hong seedlings and is recommended for summer nursery cultivation in Northeast China.

Branched-chain amino acids (BCAAs) are essential amino acids involved in protein synthesis and energy metabolism. Because animals cannot synthesize BCAA de novo, plant-derived BCAAs are important to human nutrition. Although mungbean sprouts are widely consumed as functional plant-based food materials, changes in individual BCAA accumulation and their transcriptional regulation during mungbean germination remain poorly understood. In this study, amino acid contents and transcriptomic profiles were analyzed at three germination stages, 8H, 24H, and 72H. Total BCAA content increased during germination, whereas individual BCAAs exhibited distinct temporal accumulation patterns. Isoleucine and valine increased until 72H, while leucine increased during early germination and decreased after 24H. Transcriptome analysis revealed time-dependent expression changes in BCAA biosynthesis and degradation genes associated with the leucine decrease after 24H. These findings suggest that 24H represents an important transition point for BCAA accumulation and compositional change during mungbean germination. This study provides molecular evidence for the regulation of BCAA metabolism during mungbean germination and supports the potential use of germinated mungbean as a plant-based amino acid resource.

Pepper fruit accumulated xanthophyll acyl esters during ripening. To characterize the genes involved, cDNAs for two putative xanthophyll acyltransferases named CaPYP1 and CaPYP1-like were cloned. The deduced amino acid sequences of CaPYP1 and CaPYP1-like had conserved hydrolase and acyltransferase domains. Phylogenetic analyses showed that both putative acyl transferases were conserved in Viridiplantae, suggesting important functions for both. CaPYP1 and CaPYP1-like GFP-fusion proteins were localized in the plastid when expressed in leaf tissue. Gene expression analyses indicated that both genes for CaPYP1 and CaPYP1-like were most expressed in ripening fruit (52 to 64 days after anthesis) and senescent leaf, CaPYP1 having relatively greater expression than CaPYP1-like. In virus-induced gene silencing experiments in pepper, xanthophyll esterification was greatly diminished when CaPYP1 was silenced with a simultaneous change in the ripening fruits color from dark red to bright red. In complementation tests, overexpression of CaPYP1 in a tomato mutant impaired for petal coloration and xanthophyll esterification, resulted in restoration of the petal color and the synthesis of both mono, diacyl and tri esters of xanthophylls. CaPYP1-like overexpression in the same genetic background resulted in the synthesis of relatively smaller amounts of xanthophyll monoesters. In an in vitro test, zeaxanthin was more sensitive to light than zeaxanthin dipalmitate but both were protected when triacylglycerol was mixed with it, suggesting that acyl moieties could improve xanthophyll stability. Together our results indicate that xanthophyll esterification during pepper fruit ripening is important for fruit color, xanthophyll accumulation and stability and is orchestrated by both CaPYP1 and CaPYP1-like with CaPYP1 playing a major role. HighlightRipening pepper fruit accumulates xanthophyll fatty acyl esters associated with nutritional quality and fruit color. The fruit expresses CaPYP1 and CaPYP1-like, two putative acyltransferases in their chromoplasts. In a tomato mutant impaired for xanthophyll esterification, transgenic expression of CaPYP1 promoted more xanthophyll esterification in ripe fruit than expressing CaPYP1-like.

Light quality acclimation is one of the key drivers of cyanobacterial physiology, ecology, and productivity. Although chromatic acclimation type 3 (CA3) is the canonical example of light quality-driven phycobilisome remodeling, full-PAR physiological characterization of CA3 strains has so far been limited. Here, we characterize the spectral acclimation strategies of the cyanobacterium Nostoc sp. CCAP 1453/38 across the full photosynthetically active radiation (PAR) range. Genomic analysis confirmed Nostoc as a CA3 strain capable of dynamically adjusting phycoerythrin (PE) and phycocyanin (PC) content in its phycobilisome (PBS) rods. During cultivation under narrow-band LEDs, PE was upregulated under violet, blue and green light (435-555 nm), optimizing light harvesting primarily in the blue-green part of the PAR spectrum, while PC was upregulated under red light (633-687 nm). Beyond canonical CA3 pigment switching, Nostoc responded to wavelengths poorly absorbed by PBS in two qualitatively different ways. Under growth-constraining blue light (465 nm), the strain upregulated total PBS and photosystem II (PSII) levels and biased phycobilisome coupling toward PSII (an increased PBS-PSII/PBS-PSI ratio). However, this metabolically costly response could not overcome the underlying excitonic imbalance caused by preferential PSI excitation, resulting in a low cell division rate. Under near far-red light (687 nm), PBS-PSII coupling itself was enhanced, yet total PBS content was reduced rather than increased. Specific growth rates remained as high as under red light, suggesting that this PBS-PSII reorganization avoided the metabolic burden of antenna upregulation. These results indicate that the same underlying challenge of PSII under-excitation can trigger qualitatively different acclimation responses, only some of which are energetically affordable. Spectral acclimation thus depends not only on matching pigment composition to incident wavelengths, but also on the metabolic cost of the response. Compared with parallel datasets on CA1 and non-CA strains obtained under identical conditions, our findings extend CA3 characterization beyond the canonical green/red framework, highlight bottlenecks and advantages of light quality acclimation in Nostoc, and provide a physiological basis for optimizing light regimes in controlled cyanobacterial cultivations.

Ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBisCO), the most abundant protein on Earth, is an attractive and sustainable food ingredient owing to its favourable nutritional and techno-functional properties. Leafy vegetables are particularly rich sources of RuBisCO; however, large-scale vegetable production generates substantial quantities of residual biomass throughout agri-food supply chains. Drying is widely used to stabilise this biomass and facilitate storage, transport, and handling, yet most reported RuBisCO extraction methods have been developed for fresh material and are poorly suited to dried feedstocks. Here, we present a simple, scalable, and cost-effective process for the recovery of food-grade RuBisCO from dried leafy biomass. Using spinach, rocket, and kale as model systems, efficient protein extraction was achieved from both freshly dried leaves and commercially available leaf powders without the need for resource-intensive processing. Application of the method to spinach yielded approximately 75 mg of high-purity RuBisCO per 100 g fresh-leaf equivalent, corresponding to an extraction efficiency of [~]70%, which increased to [~]90% following supplementation with 20 mM CaCl2. The recovered protein fraction also exhibited favourable foaming capacity and foam stability, demonstrating its potential as a functional food ingredient. This work provides a practical route for the valorisation of dried vegetable residues and supports the development of circular, waste-to-value supply chains for sustainable plant protein production.

Biotechnological applications of oxygenic photosynthetic organisms depend on conversion of light energy into chemical energy through photosystems (PS). This energy can then be used to drive engineered metabolic pathways that are designed as strong electron sinks. For optimal performance, the engineered host metabolism must also be balanced with the native photoprotective electron transfer network. This includes the energy-consuming function of flavodiiron (Flv) proteins, which are universal to cyanobacteria and all other oxygenic photosynthetic organisms except angiosperms. In the cyanobacterium Synechocystis sp. PCC 6803, four different Flv proteins have been shown to function in a Mehler-like reaction within two heterodimeric forms (Flv1/Flv3 and Flv2/Flv4), donating electrons to O2 without generating oxidative stress. Previously, deleting Flv3 in the Synechocystis sucrose-producing (S02) strain was shown to cause drastic metabolic changes in S02{Delta}flv3, shifting it from photoautotrophic to mixotrophic growth (Muth-Pawlak, et al., 2024). In this study, we took an opposite approach by complementing S02 with Flv3 overexpression at different levels using RBS tuning. Interestingly, this resulted in S02oeFlv3 strains with significantly increased overall photosynthetic activity and sucrose production, enhanced cell growth, and storage compound accumulation. However, these outcomes are shown not to be due to conventional O2 photoreduction activity catalysed by Flv1/Flv3. Instead, we postulate that the observed changes are linked to the previously unidentified function of homomeric Flv3/Flv3 and the strongly increased sulphate redox metabolism. Based on extensive proteomic and metabolite analyses, we hypothesise that the Flv3 homooligomer uses sulfate metabolites directly or indirectly as the final electron acceptor instead of O2. This would also explain the upregulation of sulfate-related enzymes, as well as SQR, which passes the electrons back to the PQ pool in the Flv3 overexpression strain.

Drought is a major abiotic stress threatening plant productivity and agricultural sustainability, yet the molecular mechanisms underlying adaptive root responses to water deficit in the water use strategies continuum remain insufficiently understood, particularly in perennial crops. In this study, we explored drought responses in nine accessions belonging to three wild Vitis species (V. acerifolia, V. candicans, and V. doaniana) displaying varying drought-response strategies. Plants were subjected to moderate drought stress (40% soil water content) for three weeks under greenhouse conditions. By integrating physiological, metabolic, and transcriptomic analyses, we aimed to identify both conserved and species-specific mechanisms associated with drought adaptation. Differential expression analyses revealed a conserved core set of drought-responsive genes shared among species, including genes involved in abscisic acid signaling, reactive oxygen species detoxification, solute transport, and plant defense. In parallel, each species exhibited distinct transcriptional and metabolic signatures reflecting alternative adaptive strategies related to osmoregulation, and oxidative stress mitigation. Weighted gene co-expression network analysis (WGCNA) further revealed significant associations between constitutive, non-plastic gene expression and root phenotypic traits. Overall, our findings demonstrate that wild Vitis species rely on both conserved stress-responsive pathways and species-specific constitutive regulation to cope with drought stress. These results highlight the importance of root-associated traits and intrinsic regulatory networks in shaping drought adaptation and provide new targets for the development of drought-resilient grapevine rootstocks.

Soybean, a widely cultivated leguminous crop valued for its protein, amino acids, and oil, faces the challenge of maintaining protein levels, which have an inverse correlation with yield. Reducing leaf chlorophyll levels could increase seed protein levels without compromising yield; however, this is yet to be tested. Therefore, to understand the impacts of low chlorophyll mutations on soybean yield and seed composition, we screened and compared 25 low chlorophyll soybean mutants to their 11 dark green parents. PI548210 (Lincoln mutant) demonstrates a higher concentration of protein without affecting yield compared to its dark green parent PI548362 (Lincoln), suggesting it as a good candidate for further large-scale field trials. PI547555 (Y11/y11, Clark mutant) demonstrates a lower concentration of oil without impacting yield, alongside lower gross photosynthesis, but with chlorophyll levels in the pod and seed tissues that are comparable to its dark green parent PI548533 (Clark). These findings are consistent with the oil concentration of the soybean being influenced by pod and seed photosynthesis, which is correlated with pod height and row spacing. Chlorophyll levels in the leaf do not necessarily correlate with those in the pod and seed of low chlorophyll mutants, possibly due to substantially lower expression of chlorophyll synthesis genes in the pod and seed. SIGNIFICANCEO_LIPI548210 (Lincoln mutant), one of twenty-five low chlorophyll soybean mutants, demonstrates a higher concentration of soybean protein without affecting yield compared to its dark green parent (Figure 1 and Table 1). C_LIO_LIPI547555 (Y11/y11, Clark mutant), a low chlorophyll soybean mutant, demonstrates a reduced concentration of soybean oil without impacting yield, alongside lower gross photosynthesis in pod and seed tissues compared to its dark green parent (Figures 3 and Table 2). These findings suggest that the oil concentration of the soybean is influenced by pod and seed photosynthesis, which is in turn influenced by pod height and row spacing (Figure 2). C_LIO_LIChlorophyll levels in the leaf do not necessarily correlate with those in the pod and seed of low chlorophyll mutants, possibly due to substantially lower expression of chlorophyll synthesis genes in the pod and seed (Figure 5-6). C_LI O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=84 SRC="FIGDIR/small/744892v1_fig1.gif" ALT="Figure 1"> View larger version (55K): org.highwire.dtl.DTLVardef@4282dcorg.highwire.dtl.DTLVardef@9d565forg.highwire.dtl.DTLVardef@1918292org.highwire.dtl.DTLVardef@1359b1_HPS_FORMAT_FIGEXP M_FIG O_FLOATNOFigure 1.C_FLOATNO Two low chlorophyll mutants are as healthy as their dark green parents. Lincoln and its low chlorophyll mutant, left; Clark and its low chlorophyll mutant, known as Y11/y11, right. It can be seen by eye that the plants have low chlorophyll (light green/yellow leaves) but a similar growth habit to their dark green parents. See Supplemental Figures 1-4 for contrast, where low chlorophyll mutants are stunted in growth compared to their dark green parents. C_FIG O_TBL View this table: org.highwire.dtl.DTLVardef@657ec9org.highwire.dtl.DTLVardef@166e75borg.highwire.dtl.DTLVardef@df23c7org.highwire.dtl.DTLVardef@1a60124org.highwire.dtl.DTLVardef@194ed96_HPS_FORMAT_FIGEXP M_TBL O_FLOATNOTable 1.C_FLOATNO O_TABLECAPTIONComparison of seed yield, weight, seed composition between low chlorophyll mutants and their dark green parents. ANOVA is used with linear mixed model (random effect = block, fixed effect = variety). Least squares mean is used to compare. For yield and seed composition, N=4 blocks. For leaf chlorophyll (SPAD), N=40. Yield is average yield per plant (g). n.s. = not significant. C_TABLECAPTION C_TBL O_FIG O_LINKSMALLFIG WIDTH=179 HEIGHT=200 SRC="FIGDIR/small/744892v1_fig3.gif" ALT="Figure 3"> View larger version (26K): org.highwire.dtl.DTLVardef@7a368aorg.highwire.dtl.DTLVardef@192b8f0org.highwire.dtl.DTLVardef@1abb738org.highwire.dtl.DTLVardef@89e978_HPS_FORMAT_FIGEXP M_FIG O_FLOATNOFigure 3.C_FLOATNO Light response curve of low chlorophyll mutant (Y11/y11, PI547555) and its parent (Clark, PI548533). Rates of net and gross photosynthesis of low chlorophyll (white) and dark green parents (black) pods under field conditions. Each dot represents a value (n=4) {+/-}SE. We assumed that the seeds greatly inhibited the transmittance of light through the pod and used photosynthetic photon flux density for a single-side. C_FIG O_TBL View this table: org.highwire.dtl.DTLVardef@3f0528org.highwire.dtl.DTLVardef@16ba712org.highwire.dtl.DTLVardef@a5ab2aorg.highwire.dtl.DTLVardef@889254org.highwire.dtl.DTLVardef@3efa4f_HPS_FORMAT_FIGEXP M_TBL O_FLOATNOTable 2.C_FLOATNO O_TABLECAPTIONPod photosynthetic parameters for low chlorophyll mutant (Y11/y11, PI547555) and its parent (Clark, PI548533). Photosynthesis was measured 1 September through 15 September 2021 at the University of Illinois Energy Farm in Urbana, IL, USA. The statistical analysis was done using ANOVA with linear mixed model (alpha=0.05). N=4 {+/-} SEM for Clark and N=3 {+/-} SEM for Y11. C_TABLECAPTION C_TBL O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=130 SRC="FIGDIR/small/744892v1_fig2.gif" ALT="Figure 2"> View larger version (23K): org.highwire.dtl.DTLVardef@a36c26org.highwire.dtl.DTLVardef@1116c8forg.highwire.dtl.DTLVardef@ee5e61org.highwire.dtl.DTLVardef@1766712_HPS_FORMAT_FIGEXP M_FIG O_FLOATNOFigure 2.C_FLOATNO Low chlorophyll mutant (Y11/y11, PI547555) and its parent (Clark, PI548533) differ in concentration of seed oil, which interacts with height of pod and row spacing. The box plots show the median (central line), the lower and upper quartiles (box) and the minimum and maximum values (whiskers). The statistical analysis was done using ANOVA with linear mixed model (n=3 blocks, alpha=0.05). Least squares mean is used to compare. N.s., non- significant in the analysis. A. Concentration of oil in low chlorophyll mutant seeds from the upper canopy decreased by 4% compared to the dark green parent (18.2% vs 19%) while there was no difference between them in the seeds from the lower canopy (20.2% vs 20.6%). B. Schematic layout of 2013 field setting showing two different row spacings. C. Concentration of oil in low chlorophyll mutant decreased by 2% in 38cm spacing (21.4% vs 22%) while there was no difference in 19cm spacing (21.3% vs 21.7%) in 2013 field. C_FIG O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=162 SRC="FIGDIR/small/744892v1_fig5.gif" ALT="Figure 5"> View larger version (22K): org.highwire.dtl.DTLVardef@68e508org.highwire.dtl.DTLVardef@94a6ccorg.highwire.dtl.DTLVardef@152a187org.highwire.dtl.DTLVardef@1eae137_HPS_FORMAT_FIGEXP M_FIG O_FLOATNOFigure 5C_FLOATNO (greenhouse). Correlation between the level of leaf chlorophyll (x-axis: SPAD reading) and the level of immature pod or seed chlorophyll (y-axis, mg/g DW). Line represents the linear regression model. R-squared is a coefficient of determination, the percentage of the response variable variation that is explained by the linear model. Pod is labeled by the fresh weight of seeds it contained. A. Level of chlorophyll of 25-100mg pod (n=18). B. Level of chlorophyll of 100-200mg pod (n=17) . C. Level of chlorophyll of 25-100mg seed (n=17). D. Level of chlorophyll of 100-200mg seed (n=20). C_FIG O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=180 SRC="FIGDIR/small/744892v1_fig6.gif" ALT="Figure 6"> View larger version (28K): org.highwire.dtl.DTLVardef@167fd88org.highwire.dtl.DTLVardef@361472org.highwire.dtl.DTLVardef@786325org.highwire.dtl.DTLVardef@1b53855_HPS_FORMAT_FIGEXP M_FIG O_FLOATNOFigure 6.C_FLOATNO Levels of gene expression in chlorophyll synthesis pathway. A. CHL common pathway genes; Glutamyl-tRNA reductase (GluTR). Glutamate 1- semialdehyde aminotransferase (GSA-AT). ALA dehydratase (ALAD). Uroporphyrinogen III synthase (UROS). Uroporphyrinogen III decarboxylase (UROD). Protoporphyrinogen IX oxidase (PPO). B. Mg branch; Mg-chelatase (Mgch). Magnesium-protoporphyrin IX monomethyl ester cyclase (MPEC). Protochlorophyllide reductase (POR). 3,8-divinyl protochlorophyllide a 8-vinyl-reductase (4VCR). Heme pathway; Ferrochelatase (FECH). Heme oxygenase (HO). Phytochromobilin synthase (HY). Data come from Severin et al (2010). RPKM, reads per kilobase per million mapped reads. DAF, days after flowering. The source seed is experimental line A81-356022 which was generated by introgressing G. soja (PI468916) into G. max (A81-356022). C_FIG

Whether Photosystem I (PSI) core subunits accumulate prior to light exposure in developing angiosperm seedlings remains unresolved, with conflicting reports across species. Here, we investigated the presence and membrane colocalization of the PSI core subunit PsaA in etioplasts of dark-grown angiosperms representing dicot and monocot species. Immunoblotting showed that PsaA accumulates in etioplasts of all three dicot species examined (pea, Arabidopsis, and runner bean), whereas in the monocot oat it was detected only after prolonged etiolation, at substantially lower levels and with an anomalously high apparent molecular weight. Blue-native PAGE analysis reveals that a fraction of PsaA co-migrates with LPOR, PsaB, FNR, and chlorophyll synthase, suggesting co-localization within a shared membrane microdomain rather than stable complex formation. The thylakoid insertase Alb3 was more abundant in dicot etioplasts, consistent with a potential role in the early integration of PsaA into the membrane. Upon illumination, pea reached PSI functionality faster than oat, with P700 oxidation detectable 30 min earlier, linking the dark accumulation of PsaA to an accelerated photosynthetic onset. These findings demonstrate light-independent accumulation of a PSI core subunit in a species-dependent manner and point to early steps in PSI biogenesis that precede full photosynthetic complex assembly. Highlight Contrary to prevailing models, a Photosystem I core subunit PsaA accumulates in dark-grown angiosperm seedlings before light exposure, revealing light-independent early steps in photosynthetic complex biogenesis.

Parastagonospora nodorum (Berk.) Quaedvlieg, Verkley & Crousis, a necrotrophic fungal pathogen, is the causal agent for septoria nodorum blotch, a major constraint on global wheat production. Pathogen-produced necrotrophic effectors (NEs) that interact with host-sensitivity genes in an inverse gene-for-gene manner, collectively leading to effector-triggered susceptibility (ETS). Here, we investigated the transcriptional responses of two Triticum aestivum L. genotypes, Mace and Lancer, following infiltration with a novel NE, SnTox8. A total of 12,679 unique differentially expressed genes in Mace and 149 in Lancer were detected from transcriptomic analysis. In the SnTox8-sensitive cultivar, Mace, numerous defence-related genes were induced, including protein phosphorylation cascades, reactive oxygen species bursts, calcium signalling, phytohormone modulation, and suppression of photosynthesis, consistent with findings from other ETS models, in which necrotrophic fungal pathogens hijack host defence systems to proliferate. The interaction also activated genes involved in signal transduction, metabolism, membrane modification, and molecular transport, reflecting a coordinated host reprogramming that promotes cellular dysfunction and cell death, thereby facilitating necrotrophic pathogenesis. In contrast, Lancer, an SnTox8-insensitive cultivar, exhibited minimal transcriptional changes with no evidence of effector recognition or downstream defence-related activities. Overall, this study exhibited that SnTox8 manipulates kinase-mediated immune signalling and metabolic reprogramming to convert defence activation into host cell death, revealing a mechanistic basis for ETS in wheat. The identified SnTox8-Snn8-triggered processes were confirmed through additional transcriptome analysis of Mace mutants. Outcomes from this study establish a foundation for identifying, functionally characterising and validating the corresponding host susceptibility gene Snn8.

Potato is the worlds fourth major staple crop, and tuber starch is a critical dietary energy source and a food processing raw material. In this study, hybrid progenies of the high-starch cultivar Huasheng No.7 and China main commercial varieties were used as materials, high-throughput sequencing was performed on tuber samples at tuber bulking, maturation and storage stages. Combined with bioinformatics analysis, parent-progeny resequencing, SNP screening, the regulatory mechanism of tuber starch metabolism was explored. The results showed significant stage-specific transcriptional reprogramming in potato tubers: few differentially expressed genes (DEGs) were identified at tuber bulking and maturation stages, but massive transcriptional changes occurred during storage. XET family genes regulated cell wall remodeling and carbon translocation across all stages, and WRKY transcription factors specifically controlled starch homeostasis in stored tubers. The DEGs at different stage were induced by the SNPs from their parent, and the allele from the high-starch parent, Huasheng 7 may contribute the high-starch allele to the offsprings. One key gene, Soltu.DM.02G019910, which encoded {beta}-glucosidase, have a negatively relationship with tuber starch concentration. The low-starch potato breeding tubers shown higher significantly {beta}-glucosidase activity than high-starch breeding population at maturation stage. This study clarifies the molecular regulatory network of potato tuber starch metabolism and screens core regulatory genes from the tuber bulking stage to tuber storage, thereby providing theoretical support and genetic resources for molecular breeding of high-starch and storage-resistant potato varieties.

Horseweed (Erigeron canadensis) is a widely distributed annual weed that can cause significant yield losses if not properly controlled. Its phenotypic plasticity allows it to rapidly acclimate to new environmental conditions, such as drought and herbicides, such as glyphosate, with the potential for cross stress acclimatization. The objectives of this research were to uncover the physiological and genetic effects at the intersection of drought stress and glyphosate resistance. To this end, we performed greenhouse dose response experiments, RNAseq, 14C glyphosate absorption and translocation, and cuticular lipid profiling via GC/MS. Greenhouse dose-response experiments revealed that, after drought stress, there was a 2.5-3.7 fold reduction in glyphosate sensitivity via a significant reduction in glyphosate absorption, regardless if the starting population was resistant or susceptible to the field use rate already. Cuticular waxes were collected from each population with and without drought stress and were analyzed via GC/MS. When comparing total wax loads of plants grown under WW and DS conditions, we found that drought stress significantly increased total wax loads for all three populations. Additionally drought stress substantial increases the proportion of triterpenoids in the cuticle. By RNAseq, we found serval triterpenoid biosynthesis genes upregulated after drought, which likely drive the changes in cuticle composition and ultimately increased glyphosate resistance following drought. Ultimately, understanding how drought impacts glyphosate resistance is critical for maintaining optimal weed control in the changing climate. HighlightDrought stress induces changes to cuticle composition and gene expression that reduce glyphosate absorption, thereby increasing horseweeds ability to survive glyphosate application.