In silico analysis of fungal prion-like proteins for elucidating their role in plant-fungi interactions.

Prion-like proteins (PrLPs) have emerged as beneficial molecules with implications in adaptive responses. These proteins possess a conserved prion-like domain (PrLD) which is an intrinsically disordered region capable of adopting different conformations upon perceiving external stimuli. Owing to changes in protein conformation, functional characteristics of proteins harboring PrLDs get altered thereby, providing a unique mode of protein-based regulation. Since PrLPs are ubiquitous in nature and involved in diverse functions, through this study, we aim to explore the role of such domains in yet another important physiological process viz. plant-microbe interactions to get insights into the mechanisms dictating cross-kingdom interactions. We have evaluated the presence and functions of PrLPs in 18 different plant-associated fungi of agricultural importance to unravel their role in plant-microbe interactions. Of the 241,997 proteins scanned, 3,820 (~ 1.6%) were identified as putative PrLPs with pathogenic fungi showing significantly higher PrLP density than their beneficial counterparts. Further, through GO enrichment analysis, we could predict several PrLPs from pathogenic fungi to be involved in virulence and formation of stress granules. Notably, PrLPs involved in (retro)transposition were observed exclusively in pathogenic fungi. We even analyzed publicly available data for the expression alterations of fungal PrLPs upon their interaction with their respective hosts which revealed perturbation in the levels of some PrLP-encoding genes during interactions with plants. Overall, our work sheds light into the probable role of prion-like candidates in plant-fungi interaction, particularly in context of pathogenesis, paving way for more focused studies for validating their role.

Concurrent improvement of rice grain yield and abiotic stress tolerance by overexpression of cytokinin activating enzyme LONELY GUY (OsLOG).

Meristem activity is important for normal plant growth as well as adaptive plastic development under abiotic stresses. Cytokinin has been recognized to have a major role in regulating meristem function which is controlled by cytokinin activating enzymes by fine-tuning the concentrations and spatial distribution of its bioactive forms. It was previously reported that LONELY GUY (LOG) acts in the direct activation pathway of cytokinin in rice shoot meristems. LOG has a cytokinin specific phosphoribohydrolase activity, which transforms inactive cytokinin nucleotides into active free bases. Here, we explored the role of OsLOG in controlling meristem activity mediated by cytokinin and its effects on growth, development, and stress resilience of rice plants. Overexpression of OsLOG in rice led to significant alterations in cytokinin levels in the inflorescence meristem, leading to enhanced plant growth, biomass and grain yield under both non-stress as well as stress conditions such as drought and salinity. Moreover, our study provides insight into how overexpression of OsLOG improves the ability of plants to withstand stress. The OsLOG-overexpressing lines exhibit reduced accumulation of H2O2 along with elevated antioxidant enzyme activities, thereby maintaining better redox homeostasis under stress conditions. This ultimately reduces the negative impact of stresses on grain yield and improves harvest index, as evidenced by observations in the OsLOG-overexpressing lines. In summary, our study emphasizes the diverse role of OsLOG, not only in regulating plant growth and yield via cytokinin but also in enhancing adaptability to abiotic stresses. This highlights its potential to improve crop yield and promote sustainable agriculture.

Nitric oxide, energy and redox-dependent responses to hypoxia.

Hypoxia occurs when the oxygen levels fall below the levels required for mitochondria to support respiration. Regulated hypoxia is associated with quiescence, particularly in storage organs (seeds) and stem cell niches. In contrast, environmentally-induced hypoxia poses significant challenges for metabolically-active cells that are adapted to aerobic respiration. The perception of oxygen availability through cysteine oxidases, which function as oxygen-sensing enzymes in plants that control the N-degron pathway, and the regulation of hypoxia-responsive genes and processes is essential to survival. Functioning together with reactive oxygen species (ROS), particularly hydrogen peroxide and reactive nitrogen species (RNS), such as nitric oxide (•NO), nitrogen dioxide (•NO2), S-nitrosothiols (SNOs), and peroxynitrite (ONOO-), hypoxia signaling pathways trigger anatomical adaptations such as formation of aerenchyma, mobilization of sugar reserves for anaerobic germination, formation of aerial adventitious roots and hyponastic response. NO and hydrogen peroxide (H2O2) participate in local and systemic signaling pathways that facilitate acclimation to changing energetic requirements, controlling glycolytic fermentation, the GABA shunt and amino acid synthesis. NO enhances antioxidant capacity and contributes to the recycling of redox equivalents energy metabolism through the phytoglobin (Pgb)-NO cycle. Here, we summarize current knowledge, highlighting the central role of NO and redox regulation in adaptive responses that prevent hypoxia-induced death in challenging conditions such as flooding.

A glutathione-independent DJ-1/Pfp1 domain containing glyoxalase III, OsDJ-1C, functions in abiotic stress adaptation in rice.

MAIN CONCLUSION: Overexpression of OsDJ-1C in rice improves root architecture, photosynthesis, yield and abiotic stress tolerance through modulating methylglyoxal levels, antioxidant defense, and redox homeostasis. Exposure to abiotic stresses leads to elevated methylglyoxal (MG) levels in plants, impacting seed germination and root growth. In response, the activation of NADPH-dependent aldo-keto reductase and glutathione (GSH)-dependent glyoxalase enzymes helps to regulate MG levels and reduce its toxic effects. However, detoxification may not be carried out effectively due to the limitation of GSH and NADPH in plants under stress. Recently, a novel enzyme called glyoxalase III (GLY III) has been discovered which can detoxify MG in a single step without needing GSH. To understand the physiological importance of this pathway in rice, we overexpressed the gene encoding GLYIII enzyme (OsDJ-1C) in rice. It was observed that OsDJ-1C overexpression in rice regulated MG levels under stress conditions thus, linked well with plants' abiotic stress tolerance potential. The OsDJ-1C overexpression lines displayed better root architecture, improved photosynthesis, and reduced yield penalty compared to the WT plants under salinity, and drought stress conditions. These plants demonstrated an improved GSH/GSSG ratio, reduced level of reactive oxygen species, increased antioxidant capacity, and higher anti-glycation activity thereby indicating that the GLYIII mediated MG detoxification plays a significant role in plants' ability to reduce the impact of abiotic stress. Furthermore, these findings imply the potential of OsDJ-1C in crop improvement programs.

OsRR26, a type-B response regulator, modulates salinity tolerance in rice via phytohormone-mediated ROS accumulation in roots and influencing reproductive development.

MAIN CONCLUSION: OsRR26 is a cytokinin-responsive response regulator that promotes phytohormone-mediated ROS accumulation in rice roots, regulates seedling growth, spikelet fertility, awn development, represses NADPH oxidases, and negatively affects salinity tolerance. Plant two-component systems (TCS) play a pivotal role in phytohormone signaling, stress responses, and circadian rhythm. However, a significant knowledge gap exists regarding TCS in rice. In this study, we utilized a functional genomics approach to elucidate the role of OsRR26, a type-B response regulator in rice. Our results demonstrate that OsRR26 is responsive to cytokinin, ABA, and salinity stress, serving as the ortholog of Arabidopsis ARR11. OsRR26 primarily localizes to the nucleus and plays a crucial role in seedling growth, spikelet fertility, and the suppression of awn development. Exogenous application of cytokinin led to distinct patterns of reactive oxygen species (ROS) accumulation in the roots of both WT and transgenic plants (OsRR26OE and OsRR26KD), indicating the potential involvement of OsRR26 in cytokinin-mediated ROS signaling in roots. The application of exogenous ABA resulted in varied cellular compartmentalization of ROS between the WT and transgenic lines. Stress tolerance assays of these plants revealed that OsRR26 functions as a negative regulator of salinity stress tolerance across different developmental stages in rice. Physiological and biochemical analyses unveiled that the knockdown of OsRR26 enhances salinity tolerance, characterized by improved chlorophyll retention and the accumulation of soluble sugars, K+ content, and amino acids, particularly proline.

Impact of individual, combined and sequential stress on photosynthesis machinery in rice (Oryza sativa L).

Abiotic stresses such as heat, drought and submergence are major threats to global food security. Despite simultaneous or sequential occurrence of these stresses being recurrent under field conditions, crop response to such stress combinations is poorly understood. Rice is a staple food crop for the majority of human beings. Exploitation of existing genetic diversity in rice for combined and/or sequential stress is a useful approach for developing climate-resilient cultivars. We phenotyped ~400 rice accessions under high temperature, drought, or submergence and their combinations. A cumulative performance index revealed Lomello as the best performer across stress and stress combinations at the seedling stage. Lomello showed a remarkable ability to maintain a higher quantum yield of photosystem (PS) II photochemistry. Moreover, the structural integrity of the photosystems, electron flow through both PSI and PSII and the ability to protect photosystems against photoinhibition were identified as the key traits of Lomello across the stress environments. A higher membrane stability and an increased amount of leaf chlorophyll under stress may be due to an efficient management of reactive oxygen species (ROS) at the cellular level. Further, an efficient electron flow through the photosystems and, thus, a higher photosynthetic rate in Lomello is expected to act as a sink for ROS by reducing the rate of electron transport to the high amount of molecular oxygen present in the chloroplast. However, further studies are needed to identify the molecular mechanism(s) involved in the stability of photosynthetic machinery and stress management in Lomello during stress conditions.

Maize and heat stress: Physiological, genetic, and molecular insights.

Global mean temperature is increasing at a rapid pace due to the rapid emission of greenhouse gases majorly from anthropogenic practices and predicted to rise up to 1.5°C above the pre-industrial level by the year 2050. The warming climate is affecting global crop production by altering biochemical, physiological, and metabolic processes resulting in poor growth, development, and reduced yield. Maize is susceptible to heat stress, particularly at the reproductive and early grain filling stages. Interestingly, heat stress impact on crops is closely regulated by associated environmental covariables such as humidity, vapor pressure deficit, soil moisture content, and solar radiation. Therefore, heat stress tolerance is considered as a complex trait, which requires multiple levels of regulations in plants. Exploring genetic diversity from landraces and wild accessions of maize is a promising approach to identify novel donors, traits, quantitative trait loci (QTLs), and genes, which can be introgressed into the elite cultivars. Indeed, genome wide association studies (GWAS) for mining of potential QTL(s) and dominant gene(s) is a major route of crop improvement. Conversely, mutation breeding is being utilized for generating variation in existing populations with narrow genetic background. Besides breeding approaches, augmented production of heat shock factors (HSFs) and heat shock proteins (HSPs) have been reported in transgenic maize to provide heat stress tolerance. Recent advancements in molecular techniques including clustered regularly interspaced short palindromic repeats (CRISPR) would expedite the process for developing thermotolerant maize genotypes.

Role of methylglyoxal and redox homeostasis in microbe-mediated stress mitigation in plants.

One of the general consequences of stress in plants is the accumulation of reactive oxygen (ROS) and carbonyl species (like methylglyoxal) to levels that are detrimental for plant growth. These reactive species are inherently produced in all organisms and serve different physiological functions but their excessive accumulation results in cellular toxicity. It is, therefore, essential to restore equilibrium between their synthesis and breakdown to ensure normal cellular functioning. Detoxification mechanisms that scavenge these reactive species are considered important for stress mitigation as they maintain redox balance by restricting the levels of ROS, methylglyoxal and other reactive species in the cellular milieu. Stress tolerance imparted to plants by root-associated microbes involves a multitude of mechanisms, including maintenance of redox homeostasis. By improving the overall antioxidant response in plants, microbes can strengthen defense pathways and hence, the adaptive abilities of plants to sustain growth under stress. Hence, through this review we wish to highlight the contribution of root microbiota in modulating the levels of reactive species and thereby, maintaining redox homeostasis in plants as one of the important mechanisms of stress alleviation. Further, we also examine the microbial mechanisms of resistance to oxidative stress and their role in combating plant stress.

Pokkali: A Naturally Evolved Salt-Tolerant Rice Shows a Distinguished Set of lncRNAs Possibly Contributing to the Tolerant Phenotype.

Pokkali is a strong representation of how stress-tolerant genotypes have evolved due to natural selection pressure. Numerous omics-based investigations have indicated different categories of stress-related genes and proteins, possibly contributing to salinity tolerance in this wild rice. However, a comprehensive study towards understanding the role of long-noncoding RNAs (lncRNAs) in the salinity response of Pokkali has not been done to date. We have identified salt-responsive lncRNAs from contrasting rice genotypes IR64 and Pokkali. A total of 63 and 81 salinity-responsive lncRNAs were differentially expressed in IR64 and Pokkali, respectively. Molecular characterization of lncRNAs and lncRNA-miRNA-mRNA interaction networks helps to explore the role of lncRNAs in the stress response. Functional annotation revealed that identified lncRNAs modulate various cellular processes, including transcriptional regulation, ion homeostasis, and secondary metabolite production. Additionally, lncRNAs were predicted to bind stress-responsive transcription factors, namely ERF, DOF, and WRKY. In addition to salinity, expression profiling was also performed under other abiotic stresses and phytohormone treatments. A positive modulation in TCONS_00035411, TCONS_00059828, and TCONS_00096512 under both abiotic stress and phytohormone treatments could be considered as being of potential interest for the further functional characterization of IncRNA. Thus, extensive analysis of lncRNAs under various treatments helps to delineate stress tolerance mechanisms and possible cross-talk.

Lactate Dehydrogenase Superfamily in Rice and Arabidopsis: Understanding the Molecular Evolution and Structural Diversity.

Lactate/malate dehydrogenases (Ldh/Maldh) are ubiquitous enzymes involved in the central metabolic pathway of plants and animals. The role of malate dehydrogenases in the plant system is very well documented. However, the role of its homolog L-lactate dehydrogenases still remains elusive. Though its occurrence is experimentally proven in a few plant species, not much is known about its role in rice. Therefore, a comprehensive genome-wide in silico investigation was carried out to identify all Ldh genes in model plants, rice and Arabidopsis, which revealed Ldh to be a multigene family encoding multiple proteins. Publicly available data suggest its role in a wide range of abiotic stresses such as anoxia, salinity, heat, submergence, cold and heavy metal stress, as also confirmed by our qRT-PCR analysis, especially in salinity and heavy metal mediated stresses. A detailed protein modelling and docking analysis using Schrodinger Suite reveals the presence of three putatively functional L-lactate dehydrogenases in rice, namely OsLdh3, OsLdh7 and OsLdh9. The analysis also highlights the important role of Ser-219, Gly-220 and His-251 in the active site geometry of OsLdh3, OsLdh7 and OsLdh9, respectively. In fact, these three genes have also been found to be highly upregulated under salinity, hypoxia and heavy metal mediated stresses in rice.

Genomic Survey of Flavin Monooxygenases in Wild and Cultivated Rice Provides Insight into Evolution and Functional Diversities.

The flavin monooxygenase (FMO) enzyme was discovered in mammalian liver cells that convert a carcinogenic compound, N-N'-dimethylaniline, into a non-carcinogenic compound, N-oxide. Since then, many FMOs have been reported in animal systems for their primary role in the detoxification of xenobiotic compounds. In plants, this family has diverged to perform varied functions like pathogen defense, auxin biosynthesis, and S-oxygenation of compounds. Only a few members of this family, primarily those involved in auxin biosynthesis, have been functionally characterized in plant species. Thus, the present study aims to identify all the members of the FMO family in 10 different wild and cultivated Oryza species. Genome-wide analysis of the FMO family in different Oryza species reveals that each species has multiple FMO members in its genome and that this family is conserved throughout evolution. Taking clues from its role in pathogen defense and its possible function in ROS scavenging, we have also assessed the involvement of this family in abiotic stresses. A detailed in silico expression analysis of the FMO family in Oryza sativa subsp. japonica revealed that only a subset of genes responds to different abiotic stresses. This is supported by the experimental validation of a few selected genes using qRT-PCR in stress-sensitive Oryza sativa subsp. indica and stress-sensitive wild rice Oryza nivara. The identification and comprehensive in silico analysis of FMO genes from different Oryza species carried out in this study will serve as the foundation for further structural and functional studies of FMO genes in rice as well as other crop types.

Effects of sublethal single, simultaneous and sequential abiotic stresses on phenotypic traits of Arabidopsis thaliana.

Plant responses to abiotic stresses are complex and dynamic, and involve changes in different traits, either as the direct consequence of the stress, or as an active acclimatory response. Abiotic stresses frequently occur simultaneously or in succession, rather than in isolation. Despite this, most studies have focused on a single stress and single or few plant traits. To address this gap, our study comprehensively and categorically quantified the individual and combined effects of three major abiotic stresses associated with climate change (flooding, progressive drought and high temperature) on 12 phenotypic traits related to morphology, development, growth and fitness, at different developmental stages in four Arabidopsis thaliana accessions. Combined sublethal stresses were applied either simultaneously (high temperature and drought) or sequentially (flooding followed by drought). In total, we analysed the phenotypic responses of 1782 individuals across these stresses and different developmental stages. Overall, abiotic stresses and their combinations resulted in distinct patterns of effects across the traits analysed, with both quantitative and qualitative differences across accessions. Stress combinations had additive effects on some traits, whereas clear positive and negative interactions were observed for other traits: 9 out of 12 traits for high temperature and drought, 6 out of 12 traits for post-submergence and drought showed significant interactions. In many cases where the stresses interacted, the strength of interactions varied across accessions. Hence, our results indicated a general pattern of response in most phenotypic traits to the different stresses and stress combinations, but it also indicated a natural genetic variation in the strength of these responses. This includes novel results regarding the lack of a response to drought after submergence and a decoupling between leaf number and flowering time after submergence. Overall, our study provides a rich characterization of trait responses of Arabidopsis plants to sublethal abiotic stresses at the phenotypic level and can serve as starting point for further in-depth physiological research and plant modelling efforts.

DTH8 overexpression induces early flowering, boosts yield, and improves stress recovery in rice cv IR64.

Rice yield and heading date are the two discrete traits controlled by quantitative trait loci (QTLs). Both traits are influenced by the genetic make-up of the plant as well as the environmental factors where it thrives. Drought and salinity adversely affect crop productivity in many parts of the world. Tolerance to these stresses is multigenic and complex in nature. In this study, we have characterized a QTL, DTH8 (days to heading) from Oryza sativa L. cv IR64 that encodes a putative HAP3/NF-YB/CBF subunit of CCAAT-box binding protein (HAP complex). We demonstrate DTH8 to be positively influencing the yield, heading date, and stress tolerance in IR64. DTH8 up-regulates the transcription of RFT1, Hd3a, GHD7, MOC1, and RCN1 in IR64 at the pre-flowering stage and plays a role in early flowering, increased number of tillers, enhanced panicle branching, and improved tolerance towards drought and salinity stress at the reproductive stage. The presence of DTH8 binding elements (CCAAT) in the promoter regions of all of these genes, predicted by in silico analysis of the promoter region, indicates the regulation of their expression by DTH8. In addition, DTH8 overexpressing transgenic lines showed favorable physiological parameters causing less yield penalty under stress than the WT plants. Taken together, DTH8 is a positive regulator of the network of genes related to early flowering/heading, higher yield, as well as salinity and drought stress tolerance, thus, enabling the crops to adapt to a wide range of climatic conditions.

Physiological and molecular signatures reveal differential response of rice genotypes to drought and drought combination with heat and salinity stress.

Rice is the staple food for more than 3.5 billion people worldwide. The sensitivity of rice to heat, drought, and salinity is well documented. However, rice response to combinations of these stresses is not well understood. A contrasting set of rice genotypes for heat (N22, Gharib), drought (Moroberekan, Pusa 1121) and salinity (Pokkali, IR64) were selected to characterize their response under drought, and combination of drought with heat and salinity at the sensitive seedling stage. Sensitive genotypes (IR64, Pusa 1121, Gharib) recorded higher reactive oxygen species accumulation (20-40%), membrane damage (8-65%) and reduction in photosynthetic efficiency (10-23%) across the stress and stress combinations as compared to stress tolerant checks. On the contrary, N22 and Pokkali performed best under drought + heat, and drought + salinity combination, respectively. Moreover, gene expression pattern revealed the highest expression of catalase (CAT), ascorbate peroxidase (APX) and GATA28a in N22 under heat + drought, whereas the highest expression of CAT, APX, superoxide dismutase (SOD), DEHYDRIN, GATA28a and GATA28b in Pokkali under drought + salinity. Interestingly, the phenotypic variation and expression level of genes highlighted the role of different set of physiological traits and genes under drought and drought combination with heat and salinity stress. This study reveals that rice response to stress combinations was unique with rapid readjustment at physiological and molecular levels. Moreover, phenotypic changes under stress combinations showed substantial adaptive plasticity in rice, which warrant further investigations at molecular level. Supplementary Information: The online version contains supplementary material available at 10.1007/s12298-022-01162-y.

Glyoxalase III enhances salinity tolerance through reactive oxygen species scavenging and reduced glycation.

Methylglyoxal (MG) is a metabolically generated highly cytotoxic compound that accumulates in all living organisms, from Escherichia coli to humans, under stress conditions. To detoxify MG, nature has evolved reduced glutathione (GSH)-dependent glyoxalase and NADPH-dependent aldo-keto reductase systems. But both GSH and NADPH have been reported to be limiting in plants under stress conditions, and thus detoxification might not be performed efficiently. Recently, glyoxalase III (GLY III)-like enzyme activity has been reported from various species, which can detoxify MG without any cofactor. In the present study, we have tested whether an E. coli gene, hchA, encoding a functional GLY III, could provide abiotic stress tolerance to living systems. Overexpression of this gene showed improved tolerance in E. coli and Saccharomyces cerevisiae cells against salinity, dicarbonyl, and oxidative stresses. Ectopic expression of the E. coli GLY III gene (EcGLY-III) in transgenic tobacco plants confers tolerance against salinity at both seedling and reproductive stages as indicated by their height, weight, membrane stability index, and total yield potential. Transgenic plants showed significantly increased glyoxalase and antioxidant enzyme activity that resisted the accumulation of excess MG and reactive oxygen species (ROS) during stress. Moreover, transgenic plants showed more anti-glycation activity to inhibit the formation of advanced glycation end product (AGE) that might prevent transgenic plants from stress-induced senescence. Taken together, all these observations indicate that overexpression of EcGLYIII confers salinity stress tolerance in plants and should be explored further for the generation of stress-tolerant plants.

Seedling-stage salinity tolerance in rice: Decoding the role of transcription factors.

Rice is an important staple food crop that feeds over half of the human population, particularly in developing countries. Increasing salinity is a major challenge for continuing rice production. Though rice is affected by salinity at all the developmental stages, it is most sensitive at the early seedling stage. The yield thus depends on how many seedlings can withstand saline water at the stage of transplantation, especially in coastal farms. The rapid development of "omics" approaches has assisted researchers in identifying biological molecules that are responsive to salt stress. Several salinity-responsive quantitative trait loci (QTL) contributing to salinity tolerance have been identified and validated, making it essential to narrow down the search for the key genes within QTLs. Owing to the impressive progress of molecular tools, it is now clear that the response of plants toward salinity is highly complex, involving multiple genes, with a specific role assigned to the repertoire of transcription factors (TF). Targeting the TFs for improving salinity tolerance can have an inbuilt advantage of influencing multiple downstream genes, which in turn can contribute toward tolerance to multiple stresses. This is the first comparative study for TF-driven salinity tolerance in contrasting rice cultivars at the seedling stage that shows how tolerant genotypes behave differently than sensitive ones in terms of stress tolerance. Understanding the complexity of salt-responsive TF networks at the seedling stage will be helpful to alleviate crop resilience and prevent crop damage at an early growth stage in rice.

Shaping the root system architecture in plants for adaptation to drought stress.

Root system architecture plays an important role in plant adaptation to drought stress. The root system architecture (RSA) consists of several structural features, which includes number and length of main and lateral roots along with the density and length of root hairs. These features exhibit plasticity under water-limited environments and could be critical to developing crops with efficient root systems for adaptation under drought. Recent advances in the omics approaches have significantly improved our understanding of the regulatory mechanisms of RSA remodeling under drought and the identification of genes and other regulatory elements. Plant response to drought stress at physiological, morphological, biochemical, and molecular levels in root cells is regulated by various phytohormones and their crosstalk. Stress-induced reactive oxygen species play a significant role in regulating root growth and development under drought stress. Several transcription factors responsible for the regulation of RSA under drought have proven to be beneficial for developing drought tolerant crops. Molecular breeding programs for developing drought-tolerant crops have been greatly benefitted by the availability of quantitative trait loci (QTLs) associated with the RSA regulation. In the present review, we have discussed the role of various QTLs, signaling components, transcription factors, microRNAs and crosstalk among various phytohormones in shaping RSA and present future research directions to better understand various factors involved in RSA remodeling for adaptation to drought stress. We believe that the information provided herein may be helpful in devising strategies to develop crops with better RSA for efficient uptake and utilization of water and nutrients under drought conditions.

Genetic Conservation of CBS Domain Containing Protein Family in Oryza Species and Their Association with Abiotic Stress Responses.

Crop Wild Relatives (CWRs) form a comprehensive gene pool that can answer the queries related to plant domestication, speciation, and ecological adaptation. The genus 'Oryza' comprises about 27 species, of which two are cultivated, while the remaining are wild. Here, we have attempted to understand the conservation and diversification of the genes encoding Cystathionine ß-synthase (CBS) domain-containing proteins (CDCPs) in domesticated and CWRs of rice. Few members of CDCPs were previously identified to be stress-responsive and associated with multiple stress tolerance in rice. Through genome-wide analysis of eleven rice genomes, we identified a total of 36 genes encoding CDCPs in O. longistaminata, 38 in O. glaberrima, 39 each in O. rufipogon, O. glumaepatula, O. brachyantha, O. punctata, and O. sativa subsp. japonica, 40 each in O. barthii and O. meridionalis, 41 in O. nivara, and 42 in O. sativa subsp. indica. Gene duplication analysis as well as non-synonymous and synonymous substitutions in the duplicated gene pairs indicated that this family is shaped majorly by the negative or purifying selection pressure through the long-term evolution process. We identified the presence of two additional hetero-domains, namely TerCH and CoatomerE (specifically in O. sativa subsp. indica), which were not reported previously in plant CDCPs. The in silico expression analysis revealed some of the members to be responsive to various abiotic stresses. Furthermore, the qRT-PCR based analysis identified some members to be highly inducive specifically in salt-tolerant genotype in response to salinity. The cis-regulatory element analysis predicted the presence of numerous stress as well as a few phytohormone-responsive elements in their promoter region. The data presented in this study would be helpful in the characterization of these CDCPs from rice, particularly in relation to abiotic stress tolerance.