CO2 levels are known to have an impact on plant development and physiology. In the current study, we have investigated the effect of elevated CO2 on flowering and its regulation through miRNA mediated sugar signaling. We also unraveled small RNA transcriptome of pigeonpea under ambient and elevated CO2 conditions and predicted the targets for crucial miRNAs through computational methods. The results have shown that the delayed flowering in pigeonpea under elevated CO2 was due to an imbalance in C:N stoichiometry and differential expression pattern of aging pathway genes, including SQUAMOSA PROMOTER BINDING PROTEIN-LIKE. Furthermore, qRT PCR analysis has revealed the role of miR156 and miR172 in mediating trehalose-6-phosphate dependent flowering regulation. The current study is crucial in understanding the responses of flowering patterns in a legume crop to elevated CO2 which showed a significant impact on its final yields. Also, these findings are crucial in devising effective crop improvement strategies for developing climate resilient crops, including pigeonpea.

Quantification of carbon sequestration is highly essential to assess the photosynthetic performance of tree species in the context of rising atmospheric CO2 and global warming. In the present study, we investigated the photosynthesis and carbon sequestration potential of Conocarpus erectus L. (Combretaceae), a semi—arid tree species, under present (400 µmol mol−1) as well as elevated [CO2] (550 µmol mol−1) levels. Elevated [CO2] significantly enhanced light saturated photosynthesis, water use efficiency, apparent quantum efficiency and maximum quantum yield of PS-II as compared to their ambient [CO2] counterparts demonstrating significantly enhanced photosynthetic performance. Further, plants grown under elevated [CO2] for 180 days, sequestered 33.73 kg [CO2] tree−1 while the same in ambient [CO2] was 12.89 kg [CO2] tree−1 which also resulted in 70

Cultivation of potential biofuel tree species such as Pongamia pinnata would rehabilitate saline marginal lands toward economic gains. We carried out a physiological, biochemical, and proteomic analysis to identify key regulatory responses which are associated with salt tolerance mechanisms at the shoot and root levels. Pongamia seedlings were grown at 300 and 500 mM NaCl (∼3% NaCl; sea saline equivalent) concentrations for 15 and 30 days, gas exchange measurements including leaf net photosynthetic rate (Asat ), stomatal conductance (gs ), and transpiration rate (E), and varying chlorophyll a fluorescence kinetics were recorded. The whole root proteome was quantified using the free-labeled nanoLC-MS/MS technique to investigate crucial proteins involved in signaling pathways associated with salt tolerance. Pongamia showed no visible salt-induced morphological symptoms. However, Pongamia showed about 50% decline in gas exchange parameters including Asat , E, and gs 15 and 30 days after salt treatment (DAS). The maximum potential quantum efficiency of photosystem (PS) II (Fv/Fm) was maintained at approximately 0.8 in salt-treated plants. The thermal component of PSII (DIo) was increased by 1.6-fold in the salt-treated plants. A total of 1,062 protein species were identified with 130 commonly abundant protein species. Our results also elucidate high abundance of protein species related to flavonoid biosynthesis, seed storage protein species, and carbohydrate metabolism under salt stress. Overall, these analyses suggest that Pongamia exhibited sustained leaf morphology by lowering net photosynthetic rates and emitting most of its light energy as heat. Our root proteomic results indicated that these protein species were most likely recruited from secondary and anaerobic metabolism, which could provide defense for roots against Na+ toxicity under salt stress conditions.

In the present study, an activation-tagged (AT) rice line T8-Ds-RFP3 developed has been tested for its ability to combat drought and salinity stress conditions besides analysis of its genes associated with improved productivity traits. TAIL-PCR analysis revealed the integration site of Ds element at LOC_Os03g51080 locus in the genome of the AT line. qRT-PCR analysis of glutamate decarboxylase (GAD) and F-box DUF protein-encoding genes showed more than 10- and 14-fold increased expression levels in the AT line when compared to that of wild-type (WT) plants. AT plants subjected to drought and salinity stresses exhibited enhanced stress tolerance compared to WT plants besides increased root length, tiller number and number of grains per plant. Additionally, AT plants also disclosed increased accumulation of osmolytes and antioxidants under salt and drought stress conditions owing to their enhanced ROS detoxification ability. Furthermore, AT plants also disclosed improved plant water status, photosynthetic efficiency, stomatal conductance and water use efficacy confirming their explicit stress tolerance compared to WT plants. The overall results suggest the underlying coordinated expressions of F-box DUF and GAD genes contribute to the elevated stress tolerance as well as increased productivity of the AT plants. Accordingly, the T8-Ds-RFP3 AT line can serve as a potent genetic resource for optimizing rice cultivars with increased yield potential.

World-wide crop productivity is hugely impacted by diverse eco-environmental conditions. In the present investigation, activation tagged (AT) lines of rice endowed with improved agronomic attributes have been analyzed for tolerance to salinity stress besides identification of genes associated with these attributes. Under salinity stress conditions, AT lines exhibited increased seed germination rates, improved plant growth and development at vegetative and reproductive stages as compared to wild-type (WT) plants. Furthermore, AT lines disclosed enhanced plant water content, photosynthetic efficiency, stomatal conductance, water use efficiency and maximum quantum yield when compared to WT plants, leading to improved yields and delayed onset of stress symptoms. Moreover, AT lines revealed effective antioxidant systems causing decreased accumulation of reactive oxygen species and delayed salinity stress symptoms compared to WT plants. Reduced accumulation of malondialdehyde with concomitant increases in proline and soluble sugars of AT lines further endorsing their improved stress tolerance levels. TAIL and qRT-PCR analyses of AT lines revealed Ds element integrations at different loci and respective overexpression of identified candidate genes involved in various aspects of plant development and stress tolerance. Accordingly, the AT lines plausibly serve as a rare genetic resource for fortifying stress tolerance and productivity traits of elite rice cultivars. Highlight Activation tagged lines of rice endowed with improved agronomic attributes have been analyzed for tolerance to salinity stress besides identification and expression analysis of genes associated with these attributes.

Due to rapid industrialization, the consumption of petro-products has increased, while fossil fuel resources have been gradually depleted. There has been a resurgence of interest in plant-derived biofuels as a sustainable alternative to fossil fuels for the purpose of reducing greenhouse gas emissions. Pongamia pinnata L., which is also known as Millettia pinnata is an oil-yielding, leguminous tree with a large and complex genome. Despite its multiple industrial applications, this orphan tree species has inconsistent yields and a limited understanding of its functional genomics. We assessed physiological and morphological characteristics of five high-yielding pongamia accessions and deduced important yield descriptors. Furthermore, we sequenced the genome of this potential biofuel feedstock using Illumina HiSeq, NextSeq, and MiSeq platforms to generate paired-end reads. Around 173 million processed reads amounting to 65.2 Gb were assembled into a 685 Mb genome, with a gap rate of 0.02%. The sequenced scaffolds were used to identify 30,000 gene models, 406,385 Simple-Sequence-Repeat (SSR) markers, and 43.6% of repetitive sequences. We further analyzed the structural information of genes belonging to certain key metabolic pathways, including lipid metabolism, photosynthesis, circadian rhythms, plant-pathogen interactions, and karanjin biosynthesis, all of which are commercially significant for pongamia. A total of 2,219 scaffolds corresponding to 29 transcription factor families provided valuable information about gene regulation in pongamia. Similarity studies and phylogenetic analysis revealed a monophyletic group of Fabaceae members wherein pongamia out-grouped from Glycine max and Cajanus cajan, revealing its unique ability to synthesize oil for biodiesel. This study is the first step toward completing the genome sequence of this imminent biofuel tree species. Further attempts at re-sequencing with different read chemistry will certainly improve the genetic resources at the chromosome level and accelerate the molecular breeding programs.

Salinity stress results in significant losses in plant productivity and loss of cultivable lands. Although Pongamia pinnata is reported to be a salt-tolerant semiarid biofuel tree, the adaptive mechanisms to saline environments are elusive. Despite a reduction in carbon exchange rate (CER), the unchanged relative water content provides no visible salinity induced symptoms in leaves of hydroponic cultivated Pongamia seedlings for 8 days. Our Na+-specific fluorescence results demonstrated that there was an effective apoplastic sodium sequestration in the roots. Salinity stress significantly increased zeatin (similar to 5.5-fold), and jasmonic acid (similar to 3.8-fold) levels in leaves while zeatin (similar to 2.5-fold) content increased in leaves as well as in roots of salt-treated plants. Metabolite analysis suggested that osmolytes such as myo-inositol and mannitol were enhanced by similar to 12-fold in leaves and roots of salt-treated plants. Additionally, leaves of Pongamia showed a significant enhancement in carbohydrate content, while fatty acids were accumulated in roots under salt stress condition. At the molecular level, salt stress enhanced the expression of genes related to transporters, including the Salt Overly Sensitive 2 gene (SOS2), SOS3, vacuolar-cation/proton exchanger, and vacuolar-proton/ATPase exclusively in leaves, whereas the Sodium Proton Exchanger1 (NHX1), Cation Calcium Exchanger (CCX), and Cyclic Nucleotide Gated Channel 5 (CNGC5) were up-regulated in roots. Antioxidant gene expression analysis clearly demonstrated that peroxidase levels were significantly enhanced by similar to 10-fold in leaves, while Catalase and Fe-superoxide Dismutase (Fe-SOD) genes were increased in roots under salt stress. The correlation interaction studies between phytohormones and metabolites revealed new insights into the molecular and metabolic adaptations that confer salinity tolerance to Pongamia.

Heterosis is a phenomenon wherein F 1 hybrid often displays phenotypic superiority and surpasses its parents in terms of growth and agronomic traits. Investigations on the physiological and biochemical properties of the heterotic F 1 hybrid are important to uncover the mechanisms underlying heterosis in plants. In the present study, the photosynthetic capacity of a heterotic F 1 hybrid of Zea mays L. (DHM 117) that exhibited a higher growth rate and increased biomass was compared with its parental inbreds at vegetative and reproductive stages in the field during 2017 and 2018. The net photosynthetic rate ( P n ), stomatal conductance ( g s ), transpiration rate ( E ) as well as foliar carbohydrates were higher in F 1 hybrid than parental inbreds at vegetative and reproductive stages. An increase in total chlorophyll content along with better chlorophyll a fluorescence characteristics including effective quantum yield of photosystem II ( ΔF/F m ’), maximum quantum yield of PSII ( F v /F m ), photochemical quenching ( q p ) and decreased non-photochemical quenching ( NPQ ) was observed in F 1 hybrid than the parental inbreds. Further, the expression of potential genes related to C 4 photosynthesis was considerably upregulated in F 1 hybrid than the parental inbreds during vegetative and reproductive stages. Moreover, the F 1 hybrid exhibited distinct heterosis in yield with 63% and 62% increase relative to parental inbreds during 2017 and 2018. We conclude that improved photosynthetic efficiency associated with increased foliar carbohydrates could have contributed to higher growth rate, biomass and yield in the F 1 hybrid.

In the present study, we have analyzed the seed yield and seed quality of pigeonpea grown under elevated CO2. Pigeonpea was grown for its complete life cycle in open top chambers under elevated CO2 (600 µmol/mol) and atmospheric ambient CO2 (400 µmol/mol). The growth, biomass and seed yield were increased under elevated CO2 when compared to plants grown at ambient CO2 concentrations. The mature seeds were collected after 120 days for various biochemical analyses to determine their nutritional quality. The biochemical analyses indicated that elevated CO2 grown pigeonpea seeds did not show any significant decrease in nitrogen and protein contents but showed an increase in total carbohydrates. The metabolomics of seeds revealed changes in sugars, amino acids, organic acids and fatty acid levels under elevated CO2 growth. The seeds collected from elevated CO2 grown pigeonpea showed higher levels of essential amino acids inferring their better nutritional quality. The total proteome of pigeonpea seed was studied through label-free quantification and recorded an increase in several seed specific proteins including certain stress related proteins in elevated CO2 grown pigeonpea seeds. The proteome and metabolome data demonstrate better seed vigor in elevated CO2 grown pigeonpea.

World-wide crop productivity is highly impacted by various extreme environmental conditions. In the present investigation, activation tagged (AT) line A10-Ds-RFP6 of rice endowed with improved agronomic attributes was tested for its tolerance ability against drought and salinity stress conditions as well as identification of genes associated with these traits. Under both drought and salinity stress conditions, A10-Ds-RFP6 line exhibited increased seed germination rates and improved plant growth characteristics at seedling, vegetative and reproductive stages as compared to wild-type (WT) plants. Moreover, A10-Ds-RFP6 revealed effective antioxidant systems resulting in decreased accumulation of reactive oxygen species and delayed stress symptoms compared to WT plants. Reduced accumulation of malondialdehyde with concomitant increase in proline and soluble sugars in A10-Ds-RFP6 line further endorse its improved stress tolerance levels. Furthermore, A10-Ds-RFP6 disclosed enhanced plant water content, photosynthetic efficiency, stomatal conductance, water use efficiency and maximum quantum yield compared to WT plants. TAIL and qRT-PCR analyses of AT rice line revealed the integration site of Ds element in the genome and increased expression levels of CDC48 and acetyltransferase genes involved in various aspects of plant development and stress tolerance. As such, the promising AT line plausibly serve as a rare genetic resource for fortifying stress tolerance and productivity traits of elite rice cultivars.

The contemporary global agriculture is beset with serious threats from diverse eco-environmental conditions causing decreases in crop yields by ~ 15%. These yield losses might increase further due to climate change scenarios leading to increased food prices triggering social unrest and famines. Urbanization and industrialization are often associated with rapid increases in greenhouse gases (GHGs) especially atmospheric CO2 concentration [(CO2)]. Increase in atmospheric [CO2] significantly improved crop photosynthesis and productivity initially which vary with plant species, genotype, [CO2] exposure time and biotic as well as abiotic stress factors. Numerous attempts have been made using different plant species to unravel the physiological, cellular and molecular effects of elevated [CO2] as well as drought. This review focuses on plant responses to elevated [CO2] and drought individually as well as in combination with special reference to physiology of photosynthesis including its acclimation. Furthermore, the functional role of nitrogen use efficiency (NUE) and its relation to photosynthetic acclimation and crop productivity under elevated [CO2] and drought are reviewed. In addition, we also discussed different strategies to ameliorate the limitations of ribulose-1,5-bisphosphate (RuBP) carboxylation and RuBP regeneration. Further, improved stomatal and mesophyll conductance and NUE for enhanced crop productivity under fast changing global climate conditions through biotechnological approaches are also discussed here. We conclude that multiple gene editing approaches for key events in photosynthetic processes would serve as the best strategy to generate resilient crop plants with improved productivity under fast changing climate.

Domestication and cultivation of tree species, such as Pongamia pinnata is quite important because of its biofuel properties. Seedlings grown in modified hydroponic culture were morphologically similar to that of soil grown seedlings. Further, seedlings were allowed to grow without root limitation. Comparatively, our modified hydroponic growth system can be performed with minimal resources. Prior incubated root segments with CoroNa-Green AM dye retained maximum amount of dye when compared to CoroNa-Green AM dye incubated sections. Our modified protocol provides quantitative analysis of 2D and 3D imaging process at cellular and sub-cellular level.•Our protocol is customized to study individual plant behavior.•Additionally, it is customized for growing tap rooted trees species hydroponically. Changing the nutrient solution with regular intervals provides continuous supply of nutrients to the plants.•Prior incubation of root segments with Na+ probe (CoroNa-Green AM) provides better resolution in imaging process. Additionally, both 2D and 3D imaging provides a means to acquire and analyze entirety of the sample.

Salinity stress results significant losses in plant productivity, and loss of cultivable lands. Although Pongamia pinnata is reported to be a salt tolerant semiarid tree crop, the adaptive mechanisms to saline environment are elusive. The present investigation describes alterations in hormonal and metabolic responses in correlation with physiological and molecular variations in leaves and roots of Pongamia at sea salinity level (3% NaCl) for 8 days. At physiological level, salinity induced adjustments in plant morphology, leaf gas exchange and ion accumulation patterns were observed. Our study also revealed that phytohormones including JAs and ABA play crucial role in promoting the salt adaptive strategies such as apoplasmic Na+ sequestration and cell wall lignification in leaves and roots of Pongamia. Correlation studies demonstrated that hormones including ABA, JAs and SA showed a positive interaction with selective compatible metabolites (sugars, polyols and organic acids) to aid in maintaining osmotic balance and conferring salt tolerance to Pongamia. At the molecular level, our data showed that differential expression of transporter genes as well as antioxidant genes regulate the ionic and ROS homeostasis in Pongamia. Collectively, these results shed new insights on an integrated physiological, structural, molecular and metabolic adaptations conferring salinity tolerance to Pongamia. High light Our data, for the first time, provide new insights for an integrated molecular and metabolic adaptation conferring salinity tolerance in Pongamia. The present investigation describes alterations in hormonal and metabolic responses in correlation with physiological and molecular variations in Pongamia at sea salinity level (3% NaCl) for 8 days.

Gradual soil-salinization is enhancing the proportion of non-arable salinized land areas. Developing strategies to utilize salinized lands for balanced economical productivity are highly desirable. Salt-tolerating Pongamia pinnate has gained significant attraction as a potential biofuel tree species and hence, could act as an efficient energy- crop alternative for cultivation in salinized lands. However, mechanisms conferring salt-tolerance to Pongamia are not yet demonstrated. It is highly crucial to understand the tolerance mechanisms for future breeding purposes for enhanced productivity under saline conditions. Hydroponically grown 30 days old seedlings of Pongamia are treated with two different salt concentrations (300 and 500 mM NaCl) for 8 days and analysed at regular intervals of 1, 4 and 8 days after salt exposure. Physiological parameters were recorded using infrared gas analyser and portable mini -PAM. Ion (Na+ K+, Cl-, and Ca2+) accumulation in leaves and roots were analysed through atomic absorption spectroscopy and Na+ localization was tracked through confocal laser scanning microscopy. Histochemical detection of lignin and suberin depositions in leaves and roots were carried out. Pongamia roots act as ultra-filters/strong barriers to avoid accumulation of excess Na+ levels in the leaves. The Na+ probe fluorescence analysis demonstrated effective vacuolar sequestration of Na+ in the roots. Formation of suberized multiseriate exodermis in the roots, along with extensive lignification maximized water permeability in both leaves and the roots. The present study clearly demonstrates the key cellular mechanisms conferring salinity tolerance in P. pinnata, which can be sustainably grown in salinized marginal lands as a potential biofuel tree species.

Importance of utilizing chemical desiccants to simulate terminal drought effects is gradually increasing. In the present study, a potassium iodide (KI)-simulated terminal drought stress was imposed during the full bloom (R2), pod elongation (R4), and seed initiation (R5) stages of soybean; the KI-induced desiccation effects were assessed at 1, 3, and 5 d after spraying (DASP). Plants responded to KI-simulated terminal drought stress within 1 DASP of KI-treatment, in terms of photosynthetic and transpiration rates. Seed initiation stage was found to be comparatively tolerant to KI-induced desiccation, with respect to chlorophyll degradation and PSII efficiency, which correlated well with the high hexose accumulation during this period. The present study provides a basic understanding regarding the stage-specific responses of soybean towards KI-simulated terminal drought, with respect to photosynthetic performance and sugar status and a correlation between the two traits, which could be useful for developing terminal drought-tolerant varieties.

The present study analyzed the dynamic changes in metabolites and key proteins during the seed development of Pongamia pinnata L. (Family: Fabaceae) with a particular focus on lipid biosynthesis and oil accumulation. The developing seeds were collected at four different stages: 120 (stage 1), 180 (stage 2), 240 (stage 3) and 300 (stage 4) days after flowering (DAF), representing S1, S2, S3 and S4 respectively. The analysis of seed pigments and mRNA expression patterns of key photosynthetic genes confirmed the photo-autotrophic behavior of P. pinnata seed during the initial stages of development. The metabolite profiling of developing P. pinnata seeds also revealed differentially expressed sugars, amino acids, free fatty acids and organic acids. Proteins related to development, energy metabolism, lipid accumulation as well as stress responses were documented through MALDI-TOF-MS/MS analysis. The structure and pattern of oil body accumulation at each stage of seed development were determined by electron and confocal microscopy of the cotyledonary sections. The thin layer chromatogram of P. pinnata oil revealed higher amount of Triacylglycerides and the fatty acid profile of extracted triacylglycerides showed a rapid increase in oleic acid (C18:1) at S3 and S4. The outcomes reveal new insights into the complex oleogenic metabolism during P. pinnata seed development at macro level.