Environmental and Experimental Botany

Light wavelengths modulate plant growth, metabolism, and physiology. Amaranthus, a C4 underutilized climate resilient crop with promising nutritional properties remained unexplored in terms of metabolite enrichment under monochromatic light wavelengths of visible spectrum. In current study, two cultivars of Amaranthus tricolor (green and red) were exposed to seven light regimes of photosynthetically active radiation (PAR; 400-700 nm): deep blue, blue, green, amber, red, deep red, far red, and their metabolic responses were captured using Gas Chromatography-Mass Spectrometry. The metabolic analysis revealed wavelength-specific reprogramming in the levels of organic acids, sugars, amino acids, fatty acids as well as phenolics. In both the green and red Amaranthus, branched-chain amino acids and phenylalanine, which are nutritionally essential, were significantly elevated under far-red light. While the phenolics such as caffeic acid and ferulic acid were elevated under green and deep blue light respectively in green Amaranthus, amber light wavelengths enhanced these phenolics in red Amaranthus. The study highlighted cultivar-specific metabolic rewiring triggered by specific wavelengths. Altogether, these findings provides insights into metabolic adaptation and demonstrate the ability of light wavelength to specifically enrich the targeted metabolite of nutritional relevance in Amaranthus. It offers strategies to improve the nutritional value of crops in controlled agriculture systems. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=167 HEIGHT=200 SRC="FIGDIR/small/714947v1_ufig1.gif" ALT="Figure 1"> View larger version (40K): org.highwire.dtl.DTLVardef@1a4477dorg.highwire.dtl.DTLVardef@518550org.highwire.dtl.DTLVardef@7682dorg.highwire.dtl.DTLVardef@4876e2_HPS_FORMAT_FIGEXP M_FIG C_FIG

Photosynthesis accounts for most of the final grain yield in rice, making improvements in radiation use efficiency (RUE) a key strategy for enhancing productivity. Agronomically, RUE is defined as the biomass produced per unit of total solar radiation or photosynthetically active radiation intercepted by the canopy. However, the interaction between carbon and nitrogen metabolism plays a critical role in determining plant growth and grain yield. Assimilated nitrogen is required for the synthesis of photosynthetic pigments and enzymes, while the reduction of nitrate (NOLL) and nitrite (NOLL), as well as the assimilation of ammonium (NHLL), depend on the reducing power and carbon skeletons generated by photosynthesis. In this study, two high-yielding rice (Oryza sativa) cultivars--an indica-type (El Paso 144) and a japonica-type (INIA Parao) were subjected to two nitrogen treatments (3 mM and 9 mM NOLL/NHLL) and two light intensities (850 and 1500 mol mL{superscript 2} sL{superscript 1}). A strong interaction between light intensity and nitrogen metabolism was observed, with contrasting responses between subspecies. These differences reflect a coordinated regulation of carbon assimilation and primary nitrogen metabolism. The results provide new insights into the metabolic strategies underlying nitrogen compound accumulation under variable irradiance. Such knowledge is essential for improving nitrogen fertilizer use efficiency and yield performance in elite rice genotypes cultivated under commercial field conditions.

During drought, numerous compounds accumulate in plant tissues, but their physiological roles remain unclear - they may function as osmolytes, osmoprotectants, or merely arise as by-products of stress-induced metabolic shifts. We developed an experimental approach to link accumulation patterns with specific functions, using Scots pine (Pinus sylvestris L.) saplings subjected to water deprivation and subsequent rewatering as a model system. We monitored changes in relative water content (RWC) and osmotic adjustment dynamics, employed untargeted primary metabolite profiling for preliminary screening of compounds correlated with water status, and performed quantitative GC-MS and LC-MS analyses of selected metabolites. Major inorganic cations (K, Ca{superscript 2}, Mg{superscript 2}) were also quantified to assess their potential roles. Our results revealed that tryptophan, valine, and lysine - though generally present in low abundance - exhibited selective accumulation under severely reduced RWC ([≤] 70%), suggesting their involvement as osmoprotectants. Major organic acids, particularly shikimic acid, showed trends consistent with osmotic adjustment. Notably, neither sucrose nor inorganic cations appeared to function as primary osmolytes in this context. The proposed approach offers a viable strategy for identifying compounds involved in plant adaptation to water deficit, with potential applications in breeding programs aimed at improving drought tolerance. HighlightsAn approach to identify osmolytes and osmoprotectants was implemented Accumulation of Trp, Val and Lys was consistent with their role in osmoprotection Osmotic adjustment relied predominantly on organic acids than on inorganic ions Monosaccharides but not sucrose correlates with changes in needle water status

Indica rice, being a tropical crop, is highly sensitive to cold temperature. Cold stress affects vegetative growth, photosynthetic efficiency, along with reproductive features. Genetic resource screening in diverse landraces is an approach for identifying cold-tolerant traits. Here, we have characterised a boro germplasm, CB1, with an efficient germination rate and growth vigour when treated at chilling temperatures. CB1 seedlings show a higher survival rate compared to IR36 when subjected to prolonged chilling stress. Biochemical analyses indicated efficient ROS modulation, higher chlorophyll content, enhanced photosystem II efficiency and unique stomatal traits, leading to higher relative water content in CB1 plants during stress and recovery. Transcriptome analysis supported upregulation of chlorophyll biosynthesis, photosystem, & light harvesting complex and ROS scavenger genes in CB1 seedlings. Interestingly, high D1 protein turnover in CB1 promotes damage-repair of PSII for efficient photosynthesis. Furthermore, key transcription factors for stomatal development and expression of photosynthetic genes were upregulated in CB1 during stress recovery. Notably, higher expression of OsGLK1 and enrichment of GLK1 targets were observed in CB1 plants during chilling stress and recovery. Taken together, our results suggested that CB1 plants exhibit cold tolerance by modulating photosynthesis efficiency and stomatal behavior for better adaptability and survival against chilling temperature. HIGHLIGHTSThe efficient photosynthetic recovery, active ROS scavenging system and maintenance of water content through regulating stomatal traits, enhance the survival of indica germplasm CB1 against chilling stress.

RAP2.6, an AP2/ERF transcription factor (TF), regulates plant stress responses; however, its role in floral transition remains unexplored. Here, we evaluated RAP2.6s role in flowering and the associated transcriptional changes in Arabidopsis thaliana under long-day conditions. RAP2.6-overexpressing line showed early flowering with fewer rosette leaves, whereas rap2.6-1 mutant flowered later, had more rosette leaves, and higher expression of the floral repressor FLOWERING LOCUS C (FLC). Early flowering in the overexpressing line was accompanied by transcriptional activation of the floral integrators GIGANTEA (GI), FLOWERING LOCUS T (FT), and COSTANS (CO), potentially through RAP2.6 interaction with GCC/DRE cis-regulatory elements. RAP2.6-mediated floral transition depended on nitric oxide (NO), with flowering time largely varying based on NO bioactivity. RAP2.6 was found to be a downstream regulator of Arabidopsis S-NITROSOGLUTATHIONE REDUCTASE 1 (GSNOR1) in controlling S-nitrosothiol (SNO) levels, flowering time, and silique formation. The NITRIC OXIDE-ASSOCIATED 1 (NOA1)-dependent reduction in NO levels abolished early flowering in 35S::RAP2.6 plants without affecting silique formation. Furthermore, enhanced cytokinin sensitivity and upregulation of cytokinin biosynthetic genes suggest cytokinin involvement in RAP2.6-mediated flowering. Together, these findings highlight the crucial role of RAP2.6 in regulating flowering time by integrating redox and hormonal signaling to coordinate reproductive development in A. thaliana.

Bread wheat (Triticum aestivum) is a staple food crucial for global caloric intake and food security. The current climate emergency demands the development of sustainable agricultural practices, particularly in the context of drought-induced yield reductions in bread wheat. Microalgae-based biostimulants have emerged as promising tools to enhance crop tolerance to drought stress while concurrently mitigating atmospheric CO2 accumulation. This study characterizes the transcriptomic responses to the foliar application of the microalgae-based biostimulant LRMTM in drought-stressed and fully irrigated wheat plants unveiling its mode of action. Drought stress at the tillering stage significantly altered gene expression activating key pathways related to phosphate starvation response (PSR), inositol phosphate signaling, and tocopherol biosynthesis. The application of the microalgae-based biostimulant LRMTM in drought-stressed plants further enhanced the expression of drought-responsive genes, particularly those involved in PSR and carbon fixation. Specific responses to LRMTM treatment in drought-stressed plants were also found related to abscisic acid (ABA) signaling activating genes involved in stomata closure, which plays a critical role in drought tolerance. In fully irrigated plants, LRMTM treatment was also beneficial modulating circadian rhythms, shade avoidance and attenuating stress responses. Phenotypic analysis showed that LRMTM-treated plants exhibited enhanced drought tolerance, increased height and spike length even under fully irrigated conditions. These results indicate that the microalgae-based biostimulant LRMTM not only enhances wheat response to drought but also promotes growth and productivity in both stressed and non-stressed conditions which could contribute to the development of sustainable agriculture in the face of the current climate challenges.

Napier grass (Cenchrus purpureus syn. Pennisetum purpureum), a perennial C4 forage and bioenergy crop, exhibits strong drought resilience, yet the integrative mechanisms underlying this tolerance remain incompletely understood. This study examined physiological, hydraulic, and metabolic responses of four Napier grass cultivars under PEG-induced osmotic stress and progressive soil water deficit. Drought significantly increased the root-to-shoot ratio, indicating preferential biomass allocation to roots, which supported maintenance of shoot growth and tissue water status. All cultivars showed an approximate twofold increase in water-use efficiency (WUE) under water deficit, with cv2 and cv7 displaying superior performance. Upregulation of aquaporin genes (PIP2;2 and PIP2;3) suggested active hydraulic regulation that sustained carbon assimilation under reduced transpiration. Metabolic profiling revealed pronounced root-centered osmotic adjustment, including accumulation of galactinol, myo-inositol, raffinose family oligosaccharides, proline, and several amino acids. Enhanced expression of the galactinol synthase gene confirmed activation of raffinose biosynthesis pathways. Genotypic variation highlighted cv2 as particularly drought resilient. Rapid post-stress regrowth further underscored the importance of perennial root persistence. In conclusion, drought tolerance in Napier grass arises from coordinated hydraulic resilience, osmotic adjustment, and C4 photosynthetic efficiency, supporting its suitability for forage and bioenergy production in water-limited environments. SignificantThis study shows drought tolerance in Napier grass relies on root-driven hydraulic and metabolic regulation with efficient water-use efficiency, rather than avoidance, and that PEG responses predict field performance.

The production of reactive oxygen species (ROS) in response to cadmium (Cd) has been extensively studied, demonstrating that they play a key role in the plants response to this heavy metal. While the role of enzymes like RBOHs has been thoroughly studied, the function of other ROS-producing enzymes, such as peroxisomal glycolate oxidase (GOX), remains largely overlooked. Peroxisomal GOX is a core metabolic enzyme of the photorespiratory pathway occurring in chloroplasts, mitochondria and peroxisomes. Using Arabidopsis (Arabidopsis thaliana) mutants lacking the main peroxisomal GOX genes, GOX1 (gox1-1) and GOX2 (gox2-1) we explored their function in plant response to Cd. Although photosynthetic capacity appears to be affected to the same extent in both mutants under control and Cd stress conditions, GOX2 seems to play a greater role in ROS production in response to the metal. Transcriptomic analyses on WT and gox2-1 pointed to the mitochondrial electron transport chain (mETC) as a target of Cd stress. We further investigated the individual GOX1 and GOX2 functions in mETC regulation and redox state. Although oxidative ratio of mitochondria was higher in both mutants, it was more pronounced in the absence of GOX1. Furthermore, the mETC is affected in both mutants but the regulation of its components differs in each mutant. These results point out the different functions of the two photorespiratory GOX isoforms in Arabidopsis, leading to a better understanding of the photorespiratory pathway.

C4 photosynthesis is a CO2-concentration mechanism that separates CO2 fixation between two cell types, thereby reducing photorespiration and making C4 plants more efficient than their C3 counterparts. While the C4 cycle has evolved multiple times across different genera, this study evaluates very closely related C3 and C4 species within the genus Flaveria. Apart from their carbon metabolism, C4 plants also possess adaptations in their mineral nutrition. One key nutrient which is also directly involved in photosynthesis is phosphorus. It is absorbed by the plant in the form of inorganic phosphate and is an essential component of DNA, ATP, lipids, and carbohydrates. In the Flaveria C4 species, but not in the C3 species, phosphate limitation was shown to affect the dark reactions of photosynthesis. This study investigates how phosphate deficiency impacts the light reactions in C3 and C4 Flaveria plants. We observed a differential response in the functionality of photosynthetic energy conversion between the two species. When exposed to a limited phosphate supply, the C3 species reduced its linear electron transport rate while dissipating excess energy through high-energy quenching, which was regulated by a higher pH gradient across the thylakoid membrane. In contrast, the C4 species did not regulate its photosynthetic light reaction under phosphate limitation. Instead, it exhibited increased stress levels, evidenced by a stronger biomass reduction and the induction of stress markers in the leaves. Additionally, this study uncovered an acceleration in NPQ relaxation during phosphate limitation, regardless of the photosynthesis type. HighlightPhosphate deficiency reduced linear electron transport rates and induced dissipation of excess energy through non-photochemical quenching in the C3 Flaveria species, while in the C4 species, despite elevated stress levels, the photosynthetic light reactions were unaffected.

Salinity and sodicity stresses adversely affect rice growth and yield. To overcome yield losses, suitable tolerant rice cultivars can be developed through a marker-assisted breeding (MAB) program. In the present study, genomic regions associated with sodicity stress tolerance at the reproductive stage were identified using a high-density 50kSNP array in a recombinant inbred line (RIL) population derived from the contrasting rice genotypes CSR11 and MI48. A total of 50 QTLs were detected for various yield-related traits; further, 19 QTLs with [≥]15% of phenotypic variance were selected for integrated (omics) analysis. RNA sequencing of leaves and panicles at the reproductive stage under sodic stress conditions was employed to find differentially expressed genes. A total of 1368 and 1410 SNPs; 104 and 144 indels were found for MI48 and CSR11, respectively, within the QTL regions from resequencing. At chromosomes 1 and 6, colocalized QTLs (qPH1-1/qGP1-1 and qGP6-2/qSSI6-2) were discovered. Differentially expressed genes (DEGs) were mapped over the QTL regions selected, and SNP variations and indels were screened for colocalized QTLs. Potential candidate genes, namely Os-pGlcT1 (Os01g0133400), OsHKT2;1 (Os06g0701600) and OsHKT2;4 (Os06g0701700), OsANTH12 (Os06g0699800), and OsPTR2 (Os06g0706400), were identified as being responsible for glucose transport, ion homeostasis, pollen germination, and nitrogen use efficiency, respectively, under salt stress. Finally, our study provides important insights into the genes and potential mechanisms affecting grain yield under sodic stress in rice, which will contribute to the development of molecular markers for rice breeding programs.

Climate change and increasing drought conditions significantly impedes citrus productivity in subtropical and tropical regions. This study explores the potential of combining arbuscular mycorrhizal fungi (AMF) Funneliformis mosseae and plant growth-promoting rhizobacteria (PGPR) Pseudomonas putida to mitigate drought resilience in Citrus reticulata (Red tangerine). AMF-mediated drought tolerance has been extensively documented; however, the collegial influence of PGPR and AMF on phytohormone signaling, photosynthetic efficiency, nutrient acquisition, and gene expression remains largely unexplored in citrus. We conducted a greenhouse experiment under both well water and drought stress conditions to assess the physiological and molecular responses to individual and co-inoculation with PGPR and AMF. Drought-stressed citrus plants, inoculated with AMF and PGPR, demonstrated significantly improved leaf water potential, stomatal conductance, carbon assimilation, and antioxidant defense. PGPR-AMF co-inoculation enhanced chlorophyll stability, osmotic adjustment, and nutrient uptake, while significantly reducing lipid peroxidation and ROS accumulation. The turquoise module emerged from transcriptomic and gene co-expression network analysis (WGCNA) as a potential key regulator of stress adaptation, revealed key regulatory transcription factors, e.g., CrMYB4, CrZFP8, CrSOS5, CrRGFR2, and CrQUA1, that were upregulated under combined inoculation, highlighting their potential role in stress adaptation. Our findings demonstrate that the synergistic PGPR-AMF interaction improves antioxidant enzyme activities and modulates gene expression to promote drought tolerance, providing new insights into the microbiomes role in plant resilience. These results offer a potential strategy to boost citrus growth and yield under water scarcity, with broad implications for agricultural resilience to climate change.

Low temperature stress causes significant damage to the strawberry plant. During cold stress, plants undergo morphological and physiological changes often regulated at the genetic and/or epigenetic levels. Some strawberry cultivars are more cold-hardy than others. Using the diploid woodland strawberry as a model, we analyzed the effects of cold acclimation on methylome and transcriptome dynamics in the crowns and leaves of three ecotypes with contrasting cold tolerance. Alta, which was the most cold-tolerant ecotype, exhibited the highest genetic and epigenetic plasticity in response to cold. CHH-context methylation dominated the differentially methylated regions (DMRs) with more hypomethylation in crowns and hypermethylation in leaves. CG methylation was enriched in gene bodies, while non-CG methylation was prevalent in upstream and downstream regions. Our study revealed that less than a quarter of differentially methylated genes (DMGs) showed changes in transcript accumulation levels. This finding indicates that universal cold response in Fragaria vesca, as reflected by gene expression, cannot be mechanistically attributed to DNA methylation. The majority of differentially expressed differentially methylated genes (DEDMGs) were ecotype- and tissue-specific. Enrichment analysis revealed that these genes were involved in pathways related to stress tolerance, such as carbohydrate metabolism, lipid metabolism, ATP hydrolysis, and cellular detoxification. Each ecotype responded to cold through mobilization of its own set of differentially expressed genes (DEGs), DMGs, and DEDMGs, and variation in expression and methylation patterns exhibited by Alta, FDP817, and NCGR1363 suggest that cold signaling processes and survival depend on the tissue, ecotype, and geographical origin of the plants exposed to cold stress. Therefore, this study highlights the potential of both genetic markers and epialleles as molecular markers for the development of cold-tolerant octoploid strawberry cultivars that are better suited for propagation in Nordic climates.

Soil salinization threatens global agriculture reducing yields, yet the metabolic signals controlling salt-sensitive root plasticity in alfalfa remain unclear. We hypothesize that salinity transiently uncouples the sucrose-trehalose-6-P (Tre6P)- Sucrose non-fermenting kinase 1 (SnRK1) nexus, aligning with a biphasic root metabolic response and altered root architecture. Alfalfa seedlings were grown in a hydroponic system and exposed to 200 mM NaCl, with root samples collected from 1 h to 7 d. While primary root growth and biomass remained unchanged, lateral root development was enhanced under salinity. Early response (1 h-1 d) was characterized by reduced carbon metabolites, low Tre6P, increased malondialdehyde, and SnRK1 activation, with a decline in glycolytic and TCA intermediates. During this phase, sucrose was negatively correlated with both Tre6P and SnRK1. Late response (3-7 d) showed a SnRK1 reactivation, Tre6P recovery, and osmoprotectant accumulation, including increased antioxidant capacity (+75% at 3dpt), proline (+178%), and sucrose (+18%) and starch depletion (-57%) at 7dpt respect to control. These metabolic changes coincided with the enhanced lateral root emergence. These findings indicate a two-phase response: early metabolic downscaling with transient Suc-Tre6P-SnRK1 disruption, followed by recovery with Tre6P restoration, SnRK1 reactivation, osmoprotection, and sustained root plasticity under salinity. HighlightSalinity triggers a temporary metabolic shift in alfalfa roots: plants first conserve energy, then adapt to stress, maintaining lateral root growth and flexible root architecture.

Micro-dwarf tomato cultivars are increasingly considered for urban and controlled-environment agriculture due to their compact architecture and suitability for high-density planting. However, optimal canopy management strategies for these cultivars remain poorly defined. In this study, we evaluated the effects of different leaf removal intensities on leaf-level physiological performance, fruit yield, and fruit quality in three micro-dwarf tomato cultivars (Mohammed, Hahms Gelbe Topftomate, and Red Robin) grown under contrasting seasonal light conditions. Plants were subjected to low (15%), moderate (30%), or severe (90%) leaf removal, and leaf-level gas exchange was measured across canopy layers, along with yield and fruit quality assessments. Severe leaf removal (90%) increased carbon assimilation, transpiration, and stomatal conductance in middle and lower canopy leaves by up to approximately twofold compared with control plants, indicating improved light availability at the leaf level. However, these physiological enhancements did not consistently translate into higher yield, reflecting reduced whole-plant source capacity under excessive leaf removal. Low to moderate leaf removal (15-30%) generally increased or maintained yield and fruit number, whereas severe leaf removal reduced yield in Hahms Gelbe and Red Robin, particularly under low seasonal radiation. In contrast, Mohammed exhibited yield increases of up to 220% under low leaf removal and maintained increased yield even under severe leaf removal under high-light conditions. Fruit quality was largely unaffected by leaf removal, except for total soluble solids, which declined by approximately 12% under severe leaf removal across cultivars, consistent with sugar dilution under source limitation. Overall, these results demonstrate that optimal leaf removal in micro-dwarf tomatoes requires balancing improved canopy light distribution with maintenance of sufficient leaf area for carbon assimilation. Leaf removal thresholds are strongly cultivar- and light-dependent, emphasizing the need for cultivar-specific canopy management strategies in compact tomato systems and controlled-environment agriculture.

Chilling stress induces photosystem I (PSI) photoinhibition in chilling-sensitive cucumber, in which insufficient activity of the chloroplast NADH dehydrogenase-like complex (NDH) leads to PSI over-reduction and damage. However, it is not yet clear whether these findings can be generalized to other species or what the molecular mechanism underlying impaired NDH function is. In this study, we first examined whether NDH is essential for PSI protection under chilling stress using an NDH-deficient rice mutant. Compared with wild-type plants, the NDH-deficient mutant exhibited enhanced PSI over-reduction and pronounced PSI photoinhibition under chilling stress. In contrast, rice plants expressing flavodiiron protein (FLV), which functions as an alternative electron acceptor downstream of PSI, did not exhibit PSI photoinhibition under chilling stress, demonstrating that electron sink capacity of NDH is important for PSI protection under chilling stress. Furthermore, analysis of the factors responsible for NDH dysfunction under chilling stress in cucumber revealed that chilling stress destabilizes the PSI-NDH supercomplex, leading to NDH monomerization and a consequent loss of NDH activity. This NDH monomerization is likely attributable to chilling-induced damage to the light-harvesting complex Lhca, which mediates the association between PSI and NDH. Together, these results indicate that NDH is essential for protecting PSI from photoinhibition under chilling stress in both rice and cucumber, and that chilling-induced destabilization of the PSI-NDH supercomplex represents a key molecular mechanism underlying PSI over-reduction and photoinhibition.

Amphibious plants can thrive in both terrestrial and submerged environments, which are fundamentally distinct. Although morphological plasticity of leaf known as heterophylly has been well investigated, the morphological plasticity of root in amphibious plants remains poorly understood. In this study, we discovered that an amphibious plant Callitriche palustris (Plantaginaceae), which has significant heterophylly, has a remarkable morphological plasticity also in root in response to submergence. This species develops thin roots with abundant root hairs, fewer cortical and epidermal cells, and smaller aerenchyma in the terrestrial condition. On the other hand, it develops thicker roots with few root hairs, more cortical and epidermal cells, and larger aerenchyma in the submerged condition. We call this morphological plasticity of root as "heterorhizy". Phytohormone perturbation experiments revealed that abscisic acid (ABA) and gibberellin regulate root hair development and root cell division respectively. We also found the possibility that heterorhizy was acquired in the genus Callitriche. Additionally, a similar form of root hair plasticity was also observed in the phylogenetically distinct amphibious species Ludwigia arcuata (Onagraceae). Furthermore, the absence of root hair development underwater and the similar structure of aerenchyma to C. palustris were broadly seen across diverse aquatic plants. This study provides new insights into the root morphological responses to submerged environments in aquatic plants.

Photoperiod sensitivity (PS) is a key biological response in plants as they adapt to specific environments. Rice (Oryza sativa L.) exhibits a clear PS, as it implements critical phase transition decisions based on PS signals. In this study, we identified a novel PS gene, JMJ706, that is expected to deliver photoperiod-related signals to the flowering-time regulatory network in a day-length-dependent manner. The JMJ706 mutants exhibit early flowering under LD and later flowering under SD compared to WT plants. The gene encodes an H3K9me2 demethylase, and under long-day (LD) conditions, its demethylase activity facilitates the expression of Grain number, Plant height, and Heading-date7 (Ghd7). Since Ghd7 is a floral repressor in LD, it promotes the vegetative phase by delaying flowering. Under short-day conditions (SD), H3K9me2 demethylase activity facilitates Early heading-date 1 (Ehd1) expression, and it acts as a floral accelerator by inducing Heading date 3 (Hd3a) and RICE FLOWERING LOCUS T 1 (RFT1). Furthermore, we propose that the daylength-dependent promotion of target genes (Ghd7 and Ehd1) occurs through demethylation of specific promoter regions at a crucial time window. In addition, JMJ706 may play an important role in regulating plant architecture, including plant height. The natural variation in JMJ706 alleles shows high frequencies across major rice subpopulations, suggesting that JMJ706 could play an important role in the geographical distribution and adaptation of rice cultivars. Our results may add a new layer to the rice flowering-time regulatory pathway, supporting regional adaptation and potential for future breeding.

The RETINOBLASTOMA-RELATED (RBR) protein in plants functions as a cell-cycle inhibitor, regulating cell numbers in developing organs and establishing cellular quiescence during growth. Although the role of RBR counterparts in animals also involves regulating cell size, this potential function remains unexplored in plants. We investigated transgenic Arabidopsis plants with altered RBR levels and observed corresponding changes in cell size from embryogenesis through organ development. In addition, stomatal meristemoid cells with reduced RBR levels divided beyond the size threshold, whereas elevated RBR levels increased their size. RBR stimulated terminal differentiation in the stomatal lineage by inducing MUTE and CYCLIN D5;1 expression, whereas reduced RBR levels maintained asymmetric divisions through high SPEECHLESS and CYCLIN D3;1 expression. Interestingly, the cell proliferation-dependent phosphorylation of RBR at the conserved 911Ser site positively correlated with RBR protein levels in the transgenic lines and aligned with the effect of RBR on cell size. This study discusses the potential link between RBRs control of cell proliferation and cell size, providing new insights into the coordinated regulation of plant development.

Soil salinity is a rapidly intensifying abiotic stress that significantly limits wheat productivity, particularly in coastal and irrigated agroecosystems. Although sodium (Na+) ion exclusion has been recognized as a key tolerance mechanism, the integration of physiological performance with Nax1-mediated molecular regulation among regionally adapted wheat genotypes remains insufficiently characterized. The present study aimed to dissect salinity tolerance by combining hydroponic phenotyping, multivariate trait analysis, molecular marker profiling, and quantitative expression analysis of the Na+ ion transporter gene Nax1. Seventeen spring wheat genotypes were evaluated under four salinity levels (0.0, 10, 12, and 14 dS m-{superscript 1}). Germination and survival rate, shoot and root growth, and biomass accumulation were measured. Principal component analysis (PCA) and hierarchical clustering were performed to classify genotypes, while SSR (simple sequence repeat) and Nax-linked markers assessed genetic diversity. Relative Nax1 expression was quantified using qRT-PCR (quantitative real-time polymerase chain reaction). Salinity significantly reduced germination, survival, elongation, and biomass, with strong genotype-dependent variation. Multivariate analyses clearly separated tolerant and sensitive genotypes, with biomass retention and survival contributing most to total variation. Marker analysis revealed moderate genetic polymorphism. Notably, tolerant genotypes exhibited 3-6-fold induction of Nax1 under severe salinity, positively correlating with biomass maintenance. These findings demonstrate that salinity tolerance in wheat is associated with coordinated physiological resilience and enhanced Nax1-mediated Na ion exclusion, thereby advancing mechanistic understanding and supporting molecular-assisted breeding for salt-affected environments.

Photosynthetic electron transport is mediated by several protein supercomplexes that are spatially arranged in the thylakoid membranes of chloroplasts. The chloroplast NADH dehydrogenase-like (NDH) complex is part of the photosynthetic alternative electron transport (AET) chain, which reduces the plastoquinone (PQ) pool using reduced ferredoxin as a substrate. This NDH complex is associated with photosystem I (PSI) and mediates a portion of AET in stroma lamellae, whereas photosystem II (PSII) is concentrated in grana stacks. This study presents the findings regarding post-illumination chlorophyll fluorescence increase (PIFI), a protein crucial for regulating AET via the NDH pathway. A marked increase in NDH activity and a reduction in the PQ pool in the dark were observed in PIFI-deficient mutant strains (g-pifi) generated by genome editing. Blue native PAGE analysis indicated that PIFI was associated with the NDH-PSI supercomplex in the wild type, and the NDH complex was dissociated from PSI in the g-pifi mutants. Additionally, the g-pifi mutants exhibited a decrease in the maximum quantum yield of PSII (Fv/Fm). Notably, Fv/Fm was restored in a double mutant harboring both g-pifi and NDH-deficient pnsl1 mutations, demonstrating that deregulated NDH activity in g-pifi causes downregulation of PSII efficiency. However, the lower Fv/Fm was not observed in a mutant lacking thioredoxin m4 (trxm4), which showed deregulated NDH activity but maintained the NDH-PSI supercomplex. These data suggest that PIFI stabilizes the NDH-PSI supercomplex and maintains the spatial localization of PQ reduction via AET in thylakoid membranes, which is essential for the proper functioning of PSII.