Plant Physiology and Biochemistry

Anthocyanins in the fruit peel of photosensitive eggplants exhibit a different distribution pattern compared to the photo-insensitive ones. The latter exhibits a uniform anthocyanin content, whereas photosensitive eggplants lack anthocyanin accumulation in areas not exposed to light, such as under the calyx, or have lower concentrations in less-exposed areas. In the current research work, genetic analysis of F1 and F2 populations revealed that the photo-insensitive phenotype in eggplants follows an autosomal dominant inheritance with a 3:1 ratio, indicating that the photosensitive trait is regulated by a single dominant gene. To locate and narrow down the genomic region underlying photosensitivity, a segregating F2 population was used for bulked segregant analysis sequencing (BSA-seq) and compared with previous QTLs identified in previous developed eggplants populations (ILs and MAGIC population). The accumulation of QTLs at the end of chromosome 10 postulate that chromose region as a hot spot for anthocyanin related traits. In our population all the QTLs considered overlap between the genomic region 84,1-87,9 Mb. Moreover, no DNA mutations in the progenitors of the eggplant accessions used were found. A RNA-seq analysis of bagged photosensitive and photo- insensitive eggplants was performed, as a result we identified the SmNAC1-like protein gene as a promising gene to be involved in fruit photosensitivity trait. In the photo-insensitive accession (IVIA- 371) SmNAC1-like protein was depply repressed compare to the photosensitive accession (ASI-S-1). No consistent mutations in the coding sequences (CDS) of SmNac-like protein locus among all the different eggplants accessions used were found, suggesting that other layer of regulation maybe acting in our eggplant accessions. These findings provide new insight into the regulation of the molecular mechanisms of anthocyanin biosynthesis in eggplant as point out for the first time the possible role of NAC transcription factors in the anthocyanin biosynthesis in eggplant.

The protoplast experimental system has been becoming a powerful tool for functional genomics and cell fusion breeding. However, the physiology and molecular mechanism during enzymolysis is not completely understood and has become a major obstacle to protoplast regeneration. Our study used physiological, cytology, iTRAQ (Isobaric Tags for Relative and Absolute Quantification) -based proteomic and RT-PCR analyses to compare the young leaves of sugarcane (ROC22) and protoplasts of more than 90% viability. We found that oxidation product MDA content increased in the protoplasts after enzymolysis and several antioxidant enzymes such as POD, CAT, APX, and O2- content significantly decreased. The cytology results showed that after enzymolysis, the cell membranes were perforated to different degrees, the nuclear activity was weakened, the nucleolus structure was not obvious, and the microtubules depolymerized and formed many short rod-like structures in protoplasts. The proteomic results showed that 1,477 differential proteins were down-regulated and 810 were up-regulated after enzymolysis of sugarcane young leaves. The GO terms, KEGG and KOG enrichment analysis revealed that differentially abundant proteins were mainly involved in bioenergetic metabolism, cellular processes, osmotic stress, and redox homeostasis of protoplasts, which would allow protein biosynthesis or / degradation. The RT-PCR analysis revealed the expression of osmotic stress resistance genes such as DREB, WRKY, MAPK4, and NAC were up-regulated. Meanwhile, the expression of key regeneration genes such as CyclinD3, CyclinA, CyclinB, Cdc2, PSK, CESA and GAUT were significantly down-regulated in the protoplasts. Hierarchical clustering, identification of redox proteins and oxidation products showed that these proteins were involved in dynamic networks in response to oxidative stress after enzymolysis. We used a variety of methods to figure out how young sugarcane leaves react to enzymes.

The wetting behaviour of the spray and biological efficacy of Cu2+ active ingredients in agrochemical formulations may be enhanced by tank-mix additives. We investigated how three BREAK-THRU(R) additives (BT301: biodegradable, BT133 and BT420: bio-based and biodegradable) as tank-mix with commercial copper preparations influence the spray distribution, leaf uptake and biological efficacy of copper additive mixtures against apple scab and apple powdery mildew under controlled conditions. We quantified the synergetic effects of these additives in foliar applications. In addition, we determined the phytotoxic potential and evaluated impacts on photosynthetic activity, non-photochemical quenching and ROS activity. The additives BT301 and BT420 strongly reduced surface tension and contact angle of copper treatments. The fluorescence observations revealed that BT301 achieved better spreading of copper formulation with more complete coverage of the leaf surface than BT420 and BT133, whereas "coffee-ring" spreading was observed with BT133. The additive BT301 showed an increase in relative fluorescence area, indicating higher ROS production as a signal of intra-cellular tissue activity. The photochemical efficiency of photosystem II (Fv/Fm) was not negatively influenced by copper or additive treatment. Thus, we observed no phytotoxic effects of copper-additive mixtures on apple leaves at treatment doses of 4 g Cu2+ L-1. All copper treatments reduced apple scab infestations significantly, by 53-76%. Interestingly, addition of BT301 to copper preparations showed the strongest biological efficacy (83% reduction) against V. inaequalis, whereas addition of BT420 showed the strongest effect against P. leucotricha (89% infection reduction). The synergetic effects of additives on the biological efficacy without phytotoxic effects on plants may have potential for reducing copper loads in horticultural production systems.

Cadmium is a very toxic heavy metal. We studied Cd-treated barley plants with especial focus on rare atypical plants with signs of chlorosis. Cd treatment decreased the maximal photochemical activities of both photosystems while the activity of photosystem I decreased more than activity of photosystem II. In photosystem II, Cd treatment inhibited non-photochemical quenching that increased portion of unquenched "closed" complexes of photosystem II. The latter effect increased balance of limitations between the acceptor side of photosystem II (qC) and the donor side of photosystem I (Y(ND)) and raised the ratio qC/Y(ND). All these effects were enhanced in the atypical more damaged plants. Cd treatment reduced K content in the first leaves; in atypical plants, K content decreased even more. Cd treatment changed a pattern of stomatal conductance possibly by means of reducing K content in leaves. The untreated barley plants kept different stomatal conductance at adaxial and abaxial sides of leaves and fulfilled a complicated diurnal dynamics with large ups and downs of stomatal conductance. The typical Cd-treated plants were less flexible and demonstrated medium values. Stomatal conductance in the untreated plants were higher or lower than in the typical Cd-treated plants depending on a particular time; average daytime stomatal conductance was equal in both variants. At 10.00, stomatal conductance in the atypical Cd-treated plants was smaller than in the typical ones. Levels of 13 chloroplast mRNAs remained unchanged, while psbD decreased in both types of Cd-treated plants. HighlightsO_LISeveral Cd effects were enhanced in more damaged (atypical) chlorotic plants C_LIO_LICd treatment decreased activity of photosystem I and non-photochemical quenching C_LIO_LIRatio of limitations between photosystems II and I [qC/Y(ND)] was rather constant C_LIO_LICd treatment reduced K content in the first leaves C_LIO_LICd treatment changed pattern of stomatal conductance C_LI

Autophagy is a conserved catabolic process that plays an essential role under nutrient starvation condition and influences different developmental processes. We observed that seedlings of autophagy mutants (atg2, atg5, atg7, and atg9) germinated in the dark showed delayed chloroplast development following illumination. The delayed chloroplast development was characterized by a decrease in photosynthetic and chlorophyll biosynthetic proteins, lower chlorophyll content, reduced chloroplast size, and increased levels of proteins involved in lipid biosynthesis. Confirming the biological impact of these differences, photosynthetic performance was impaired in autophagy mutants 12h post illumination. We investigated if the delayed chloroplast development could be explained by lower lipid import to the chloroplast or lower triglyceride (TAG) turnover. We observed that the limitations in the chloroplast lipid import imposed by trigalactosyldiacylglycerol1 are unlikely to explain the delay in photomorphogenesis. However, we found that lower TAG mobility in the triacylglycerol lipase mutant sugardependent1 significantly affected photomorphogenesis. Moreover, we showed that lower levels of carbon resources exacerbated the delay in photomorphogenesis whereas higher levels of carbon resources had an opposite effect. This work provides evidence that autophagic process operate during de-etiolation in a manner that contributes to photomorphogenesis through increasing lipid turnover to physically or energetically sustain photomorphogenesis.

Carotenoids are susceptible to degrading processes initiated by oxidative cleavage reactions mediated by Carotenoid Cleavage Dioxygenases that break their backbone, leading to products called apocarotenoids. These carotenoid-derived metabolites include the phytohormones abscisic acid and strigolactones, and different signaling molecules and growth regulators, which are utilized by plants to coordinate many aspects of their life. Several apocarotenoids have been recruited for the communication between plants and arbuscular mycorrhizal (AM) fungi and as regulators of the establishment of AM symbiosis. However, our knowledge on their biosynthetic pathways and the regulation of their pattern during AM symbiosis is still limited. In this study, we generated a qualitative and quantitative profile of apocarotenoids in roots and shoots of rice plants exposed to high/low phosphate concentrations, and upon AM symbiosis in a time course experiment covering different stages of growth and AM development. To get deeper insights in the biology of apocarotenoids during this plant-fungal symbiosis, we complemented the metabolic profiles by determining the expression pattern of CCD genes, taking advantage of chemometric tools. This analysis revealed the specific profiles of CCD genes and apocarotenoids across different stages of AM symbiosis and phosphate supply conditions, identifying novel markers at both local and systemic levels. HighlightOur study presents the profiles of CCD gene expression and apocarotenoids across different stages of AM symbiosis and Pi supply conditions and reveals novel AM markers at both local and systemic levels.

Photosynthetic electron transport consists of linear electron flow and two cyclic electron flow (CEF) pathways around photosystem I (PSI). PGR5-dependent CEF-PSI is thought to be the major CEF-PSI pathway and an important regulator of photosynthetic electron transfer. Antimycin A (AA) is commonly recognized as an inhibitor of PGR5-dependent CEF-PSI in photosynthesis. Although previous findings imply that AA may also affect photosystem II (PSII), which does not participate in CEF-PSI, these "secondary effects" tend to be neglected, and AA is often used for inhibition of PGR5-dependent CEF-PSI as if it were a specific inhibitor. Here, we investigated the direct effects of AA on PSII using isolated spinach PSII membranes, and spinach and Chlamydomonas thylakoid membranes. Measurements of QA- reoxidation kinetics showed that AA affects the acceptor side of PSII and inhibits electron transport within PSII. Furthermore, repetitive Fv/Fm measurements revealed that, in the presence of QB-site binding inhibitors, AA treatment results in severe photoinhibition even from a single-turnover flash. The direct effects of AA on PSII are non-negligible and caution is required when using AA as an inhibitor of PGR5-dependent CEF-PSI. Meanwhile, we found that the commercially available compound AA3, which is a component of the AA complex, inhibits PGR5-dependent CEF-PSI without having notable effects on PSII. Thus, we propose that AA3 should be used for the physiological study of the PGR5-dependent CEF-PSI.

Dark-induced senescence triggers significant metabolic changes that recycle resources and ensure plant survival. In this study, we identified a transcription factor OsS40-14 in rice, which can form homo-oligomers. The oss40-14 knockout mutants exhibited stay-green phenotype of primary leaf and flag leaf during dark-induced condition, with substantial retention of chlorophylls and photosynthetic capacity as well as remarkably reduced reactive oxygen species (ROS), while OsS40-14 overexpressing transgenic lines (oeOsS40-14) showed an accelerated senescence phenotype under dark-induced leaf senescence conditions. Transcriptome analysis revealed that when the detached leaves of oss40-14 and WT were treated in darkness condition for 72 hours, 1585 DEGs (|Log2FC| [&ge;]1, P value<0.05) were reprogrammed in oss40-14 relative to WT. CUT&Tag-seq analysis in protoplast transient expression of OsS40-14 system showed that OsS40-14 was 40.95% enriched in the transcription start site (TSS) of the genome. Sequence clustering analysis showed that OsS40-14 protein was mainly enriched and bound to TACCCACAAGACAC conserved elements. The seed region "ACCCA" of OsS40 proteins was identified by single nucleotide mutagenesis EMSA. The integrative analysis of transcriptome and CUT&Tag-seq datasets showed 153 OsS40-14-targeted DEGs, they mainly enriched in plastid organization and photosynthesis process at dark-induced condition in oss40-14 relative to WT. Among them, eleven candidate targets of OsS40-14 such as Glucose 6-phosphate/phosphate translocator, Na+/H+ antiporter, Catalase, Chitinase 2, Phosphate transporter 19, OsWAK32, and OsRLCK319 were directly targeted and upregulated confirmed by ChIP-PCR and RT-qPCR. It demonstrates a novel model of OsS40-14 mediating macromolecule metabolism and nutrient recycling controls the plastid organization during dark-induced leaf senescence. Significant statementInvolvement of OsS40-14 in macromolecule catabolism, nutrient recycling, and ROS homeostasis revealed a plastid organization defection of dark-induced senescence in rice

Phosphorylation of the core subunits of photosystem II (PSII) is largely governed by a protein kinase and an antagonistic protein phosphatase. In plants the respective mutants show alterations in the architecture of thylakoid membranes and in the repair of PSII after photo-inhibition. However the protein kinase targets several subunits of PSII, as well as other proteins. To specifically investigate the role of phosphorylation of the different PSII subunits, we used site-directed mutagenesis and chloroplast transformation in Chlamydomonas reinhardtii. Major, evolutionarily-conserved sites of phosphorylation in three components of PSII (CP43, D2 and PsbH) were mutated to replace the corresponding serine or threonine residues with alanine. The alanine substitution mutant of D2 had no apparent phenotype, while the mutant of CP43 presented a minor delay in recovery from photo-inhibition. Alanine substitutions of the phosphorylation sites in PsbH had significant effects on the accumulation of PSII or on its recovery from photo-inhibition. When mutations in two of the target subunits were combined through a second cycle of chloroplast transformation, the strongest phenotype was observed in the mutant lacking phosphorylation of both PsbH and CP43, which showed delayed recovery from photo-inhibition. Surprisingly this phenotype was reversed in the mutant defective for phosphorylation of all three subunits. Our analysis indicates a prominent role for the N-terminus of PsbH in the stable accumulation of PSII and of PsbH phosphorylation in its repair cycle.\n\nSIGNIFICANCE STATEMENTTo specifically investigate the role of PSII phosphorylation, alanine-substitution mutants of the major phospho-sites in the subunits of PSII were generated individually or in combinations using chloroplast transformation. PSII assembly was defective in some of the PsbH mutants. PSII repair after photo-inhibition was delayed most strongly in the mutant lacking phosphorylation of both PsbC (CP43) and PsbH.

Microalgae, and among them, the diatom Phaeodactylum tricornutum stand out with their remarkable versatility and metabolic engineering potential. Diatoms exhibit substantial variability in metabolism, photosynthetic physiology and environmental adaptation, even across the same species. These factors can affect the design and outcome of metabolic engineering strategies. In this study, we profiled the diversity of biotechnologically relevant traits of three P. tricornutum strains (Pt1, Pt6, and Pt9) under different light regimes to identify the most suitable chassis to be employed as bio-factory to produce high-value terpenoids. We conducted detailed assessments of these strains, using pulse amplitude modulated (PAM) fluorometry to measure photosynthetic efficiency and we analyzed the composition of pigments and triterpenoids, as main terpenoid metabolic sinks. Parameters such as the maximum quantum yield of PSII (Fv/Fm), the efficiency of excitation energy capture (Fv/Fm), and OJIP kinetics were used to estimate photosynthetic performance in different light regimes. Additionally, we evaluated their transformation efficiency and their capacity to produce heterologous monoterpenoids, using geraniol as a model product. Our findings revealed that Pt1, widely used in laboratories, exhibits robust growth and photosynthetic performance under standard laboratory conditions. Pt6, adapted to intertidal environments, shows unique resilience in fluctuating conditions, while Pt9, with its high-temperature tolerance, excels under continuous high irradiance. Additionally, this variability across strains and light conditions influenced the metabolic output of each strain. We concluded that understanding the physiological responses of different P. tricornutum strains to light is crucial for optimizing their use in metabolic engineering. The insights gained from this research will facilitate the strategic selection and exploitation of these strains in algae biotechnology, enhancing the production of commercially valuable compounds such as high-value terpenoids and derivatives. This comprehensive characterization of strains under varying light conditions offers a pathway to more efficient and targeted metabolic engineering applications. HighlightsO_LIPt1, Pt6, and Pt9 exhibit distinct physiology under different light regimes. C_LIO_LIPt9 is photosynthetically more performant in continuous light, Pt6 in photoperiod. C_LIO_LILight regimes affect pigments and triterpenoid content in all three strains. C_LIO_LIEach strain exhibits a specific carotenoid and triterpenoid composition. C_LIO_LIBacterial conjugation of episomes varies across strains, it is more efficient in Pt1. C_LIO_LIPt1 is suited for the heterologous synthesis of monoterpenes (geraniol). C_LI

Seed deterioration during storage results in poor germination, reduced seed vigor, and non-uniform seedling emergence. The rate of aging depends on storage conditions (RH, temperature, and oxygen) and genetic factors. This study aims to identify these genetic factors determining the longevity of rice seeds stored under experimental aging conditions mimicking long-term dry storage. Genetic variation for tolerance to aging was studied in 300 Indica rice accessions and storing dry seeds under elevated partial pressure of oxygen (EPPO) condition, using a genome-wide association study. The association analysis yielded eleven unique regions across the genome for all measured germination parameters after aging. These genomic regions differed from regions previously identified in rice under humid experimental aging conditions. The significant single nucleotide polymorphism in the most prominent region was located within the Rc gene, encoding a bHLH transcription factor. Storage experiments using isogenic rice lines (SD7-1D (Rc) and SD7-1d (rc)) with the same allelic variation confirmed the functional role of the Rc gene, conferring a stronger tolerance to dry EPPO aging. A functional Rc gene results in the accumulation of pro-anthocyanidins in the pericarp of rice seeds, an important sub-class of flavonoids having strong antioxidant activity, which may explain why genotypes with an allelic variation for this gene show variation in seed tolerance to dry EPPO aging.

Cassava (Manihot esculentum Crantz) is a staple food source for many developing countries. Its edible roots are high in starch but lack micronutrients such as {beta}-carotene. In the present study, analysis of pedigree breeding populations has led to the identification of cassava accessions with enhanced {beta}-carotene contents up to 40 g/g DW. This represents 0.2% of the Recommended Daily Allowance (RDA) for vitamin A. The {beta}-branch of the carotenoid pathway predominates in cassava roots, with dominant levels of {beta}-carotene followed by other minor epoxides of {beta}-ring derived carotenoids. Metabolomic analysis revealed that steady state levels of intermediary metabolism were not altered by the formation of carotenoids, similar to starch and carbohydrate levels. Apocarotenoids appeared to be independent of their carotenoid precursors. Lipidomic analysis provided evidence of a significant positive correlation between carotenoid and lipid content, in particular plastid specific galactolipids. Proteomic analysis of isolated amyloplasts revealed an abundance of carbohydrate/starch biosynthetic associated proteins (e.g. glucose-1-phosphate adenylyltransferase). No carotenoid related proteins were detected even in the highest carotenoid containing lines. Carotenoids were associated with fractions typically annotated as plastoglobuli and plastid membranes (particularly the envelope). Proteomic analysis confirmed these structures apart from plastoglobuli, thus potentially amyloplast structures may not contain classical plastoglobuli structures. HighlightCassava genotypes with enhanced provitamin A content ({beta}-carotene) reveals interconnectivity between the carotenoid pathway, starch and lipid biosynthesis.

Age affects the production of secondary metabolites, but how developmental cues regulate secondary metabolism remains poorly understood. Annatto (Bixa orellana L.) is a source of bixin, an apocarotenoid used in the worlds food industry worldwide. Understanding how age-dependent mechanisms control bixin biosynthesis is of great interest for plant biology and for pharmaceutical, cosmetic, and textile industries. Here, we used genetic and molecular tools to unravel the role of the annatto age regulated miRNA156 (miR156) targeted SQUAMOSA PROMOTER BINDING PROTEIN LIKE (BoSPL) genes in secondary metabolism. Low expression of several BoSPL genes in miR156 overexpressing annatto plants (OE::156) impacted leaf ontogeny, reducing bixin production and increasing abscisic acid (ABA) levels. Modulation of BoCCD4;4 and BoCCD1 expression, key genes in lycopene cleavage, was associated with diverting the carbon flux from bixin to ABA, whereas upregulation of lycopene {beta} cyclase genes implies the xanthophyll biosynthetic pathway acted as a carbon sink in OE::156 plants. Proteomic analyses revealed low accumulation of most secondary metabolite-related enzymes in OE::156 plants, suggesting that miR156 targeted BoSPLs are required to activate several annatto secondary metabolic pathways. Our findings suggest that carbon flux in B. orellana OE::156 leaves was redirected from bixin to ABA production, indicating an age-dependent leaf dynamics of bixin biosynthesis. Importantly, our study opened a new venue to future annatto breeding programs aiming to improve bixin output.

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.

Verticillium wilt is the most devastating disease of cotton and it results in huge yield losses every year in the fields. The underlying mechanisms of VW in cotton are not well explored yet. In the current approach we used the transcriptome data from G. australe in response to Verticillium wilt attack to mine the ERF TFs and prove their potential role in resistance against VW attack in cotton. We identified 23 ERFs in total, and on the basis of expression at different time points i.e., 24h, 48h and 72h post inoculation and selected GauERF105 for further validation. We performed VIGS in cotton and over expression in Arabidopsis respectively. Moreover, DAB and trypan staining also suggests that the impact of disease was more in the wildtype as compared to transgene lines. On the basis of our results, we confirmed that GauERF105 is the key candidate and playing a key role for defending cotton against VW attack. Current finding might be helpful for generating resistance germplasm in cotton and it will be beneficial to recover the yield losses in field.

Duckweeds contain relatively high levels of starch and are a potential biomass feedstock for biofuel production. Here, the biomass and starch yield of duckweed under three different nutrient-limited conditions were analyzed to investigate possible ways of further increasing the efficiency of starch production. The results showed that sulfur limitation resulted in the highest starch yield, which was 42% and 73% higher than in nitrogen or phosphorus limitation, respectively. The high yield of sulfur-limited duckweed is largely due to the combinations of little effects on biomass and high accumulations of starch. Although nitrogen limitation led to higher starch content (67.4%), it severely reduced biomass production. The photosynthetic performance indicator Fv/Fm was a simple and sensitive indicator of starch content in nutrient-limited duckweed. Taken together, this study demonstrates that sulfur limitation is a simple and efficient way to increase starch yield, highlighting the great potential of duckweed for biofuel production. We report that sulfur limitation is a practical approach to increase starch yields in duckweed without affecting growth or biomass. HighlightsO_LISulfur limitation induces starch production in a duckweed specie. C_LIO_LINitrogen limitation triggers the highest starch content, but limits growth. C_LIO_LISulfur limitation results in the highest starch yield. C_LIO_LIFv/Fm is a rapid and robust proxy of starch content in nutrient-limited duckweed. C_LI

Heterogeneous distribution of PSI and PSII in thick grana in shade chloroplasts is argued to hinder spillover of chlorophyll excitations from PSII to PSI. To examine this dogma, we measured fluorescence induction at 77K at 690 nm (PSII) and 760 nm (mainly PSI) in the leaf discs of Spinacia oleracea, Cucumis sativus and shade tolerant Alocasia odora, grown at high and low light, and quantified their spillover capacities. PSI fluorescence (FI) consists of the intrinsic PSI fluorescence (FI) and fluorescence caused by excitations spilt over from PSII (FI{beta}). When FI and FII parameters between State 1 and State 2, induced by weak far-red and blue light, were compared, PSII maximum fluorescence (FIIm) and FI{beta} were greater, and FI was smaller in State 1 and thereby the spillover ratio, FI{beta}/(FI +FI{beta}) or FI{beta}/FIm, was greater in State 1. Since the leftover FIIm was found to be about 10% of total Fm at 760 nm, all the data were corrected. Even after the correction, the spillover ratio in FIm in State 1 ranged from 21 to 32%, and the spillover ratios were comparable irrespective of growth light conditions. Although extensive grana in low light grown plants would suggest that PSII and PSI are too separated for spillover, in A. odora chloroplasts, the ratio of non-appressed thylakoid membranes/total thylakoid membranes was little affected by growth light and more than 40%. Abundant non-appressed thylakoids would contribute to efficient spillover.

Methylglyoxal (MGO), toxic byproduct of glycolysis, acts as a signaling molecule at low levels, but its over-accumulation during drought stress disrupts redox balance and accelerates cell death. Contrarily, melatonin maintains redox balance, particularly during stress. The redox status and MGO level might differ in drought-sensitive and drought-tolerant varieties, so shall the melatonins effect. The study evaluated the effect of melatonin-priming on MGO detoxification and autophagy during polyethylene glycol (PEG)-induced drought stress during seed germination in drought-sensitive (L-799) and drought-tolerant (Suraj) varieties of upland cotton. Melatonin-priming increased endogenous melatonin content, reduced MGO accumulation and advanced glycation end-products (AGEs), and downregulated the expression of MGO biosynthesis genes in L-799 under stress. The expression and activities of glyoxalases and non-glyoxalases were upregulated, showing melatonins effectiveness in MGO detoxification. Additionally, priming upregulated the expression of TPI1, PGK5, and PK1 and downregulated HK3 expression, allowing better conversion of glucose to pyruvate, leading to reduced MGO in L-799. The downregulation of necrosis-related genes with reduced cell death in L-799 shows the potential of priming in maintaining cell viability under stress. Furthermore, upregulated expression of SnRK1.1, SnRK2.6 genes and KIN10 protein levels, with enhanced autophagy markers (ATGs, MDC-stained bodies, lipidated-ATG8), confirmed improved autophagy in melatonin-primed L-799 under stress. Despite lowered ABA, melatonin-mediated MGO homeostasis likely activated MAPK6, inducing autophagy independent of ABA in stressed plants. Conversely, Suraj, with higher endogenous melatonin and inherent stress tolerance, showed limited response to priming. Thus, the study illustrates melatonins role in regulating MGO homeostasis and autophagy under drought stress in cotton.

Secondary metabolites in plants have various physiological functions, including antioxidant and antibacterial activities. Previous studies have suggested genes and associated molecular mechanisms involved in the production of diverse secondary metabolites. However, much less is known about the genetic bases underlying within-species diversity in metabolite accumulation patterns, particularly in less focused tissues such as rice hulls. In this study, we aimed to identify the causal variant that affects flavonoid accumulation in rice hulls. We identified an F-box containing protein IBF1 is causal for genotypic differences in hull color through positional cloning. The variety IR64, with straw-white hulls, harbors functional IBF1 proteins that interact with a chalcone synthase, CHS1. Conversely, frame-shift mutations of IBF1 in the variety DJ123, which has pigmented hull color, resulted in a lack of a Kelch domain essential for the IBF1-CHS1 interaction. As a result, the DJ123 variant of IBF1 (IBF1DJ123) no longer interacted with CHS1, which was further supported by deep learning-based protein structural modeling. Further metabolome and transcriptome analyses using IR64 and an IR64-based chromosomal segment substitution line (CSSL) carrying IBF1DJ123 revealed an increase in the content of multiple flavonoids (such as naringenin and luteolin), while suppressing the expression of CAD involved in lignin synthesis. Metabolites in the CSSL carrying IBF1DJ123 suppressed the growth and siderophore generation activity of Pantoea species, which can act as beneficial or pathogenic endophytes. This study highlights the impact of a single gene on diverse metabolite accumulation patterns and suggests that this change may provide defense against pathogens.

Necrotic leaf spot of Curcuma longa (turmeric) limits the chief physio-biochemical activity for maintaining the plant health and productivity. In the present study, polyhouse and open field trials were conducted to estimate the pathogenicity of C. gloeosporioides on turmeric and to evaluate the foliar efficiency of propiconazole @ RD and copper oxychloride, extracts of A. indica, A. sativum and O. sanctum @ 40%, and culture filtrates of T. viride, T. harzianum and T. virens @ 4x106 cfu/ml in inducing physio-biochemical tolerance of pathogen inoculated and non-inoculated plants. In both the trials, these three agents yielded the highest efficiency to enhance the physio-biochemical traits. The induced physio-biochemical tolerance in treated turmeric plants showed variation in the elevation of plant health and immunity in response to pathogen aggressiveness or disease severity. However, phytophenol content was quite higher in infected plants than non-infected plants due to initiation of defense reaction in response of pathogenic elicitors. Thus, the present study demonstrated the novelty of physio-biochemical tolerance induction on turmeric plants by using fungicides, biocontrol agents and phytoextracts. HighlightsO_LIFoliar treatments improve desirable plant physio-biochemical traits against pathogen. C_LIO_LIPhysio-biochemical variation induces the innate plant defense system. C_LIO_LIHigh phytophenol accumulation counteracts the pathogenic stress. C_LIO_LITurmeric plants health and yield enhance by the reduction of disease intensity. C_LI