Publications of NIPGR Scientists
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Item A conserved HSF:miR169:NF-YA loop involved in tomato and Arabidopsis heat stress tolerance(John Wiley & Sons, 2022) Rao, Sombir; Gupta, Apoorva; Bansal, Chandni; Sorin, Celine; Crespi, Martin; Mathur, SaloniHeat stress transcription factors (HSFs) and microRNAs (miRNAs) regulate different stress and developmental networks in plants. Regulatory feedbacks are at the basis of these networks. Here, we report that plants improve their heat stress tolerance through HSF-mediated transcriptional regulation of MIR169 and post-transcriptional regulation of Nuclear Factor- YA (NF-YA) transcription factors. We show that HSFs recognize tomato and Arabidopsis MIR169 promoters using yeast-one-hybrid/ChIP-qPCR. Silencing tomato HSFs using virus induced gene silencing (VIGS) reduced Sly-MIR169 levels and enhanced Sly-NF- YA9/A10 target expression. Further, Sly-NF-YA9/A10-VIGS knock-down tomato plants and Arabidopsis plants overexpressing At-MIR169d or At-nf-ya2 mutants showed a link with increased heat tolerance. In contrast, Arabidopsis plants overexpressing At-NF-YA2, or those expressing a non-cleavable At-NF-YA2 form (miR169d-resistant At-NF-YA2) as well as plants inhibited for At-miRNA169d regulation (miR169d mimic plants) were more sensitive to heat stress, highlighting NF-YA as negative regulator of heat tolerance. Furthermore, post-transcriptional cleavage of NF-YA by elevated miR169 levels resulted in alleviating the repression of heat stress effectors HSFA7 in tomato and Arabidopsis revealing a retroactive control of HSFs by the miR169:NF-YA node. Hence, a regulatory feedback loop involving HSFs, miR169s and NF-YAs plays a critical role in the regulation of heat stress response in tomato and Arabidopsis plants.Item Cultivar-biased regulation of HSFA7 and HSFB4a govern high-temperature tolerance in tomato(Springer Nature Publishing AG, 2022) Rao, Sombir; Das, Jaishri Rubina; Balyan, Sonia; Verma, Radhika; Mathur, SaloniHeat shock factors (HSFs) are at the core of heat stress (HS) response in plants. However, the contribution of HSFs governing the inherent thermo-tolerance mechanism in tomato from sub-tropical hot climates is poorly understood. With the above aim, comparative expression profiles of the HSF family in a HS-tolerant (CLN1621L) and -sensitive cultivars (CA4 and Pusa Ruby) of tomato under HS revealed cultivar-biased regulation of an activator (HSFA7) and a repressor (HSFB4a) class HSF. HSFA7 exhibited strong upregulation while HSFB4a showed downregulation in tolerant tomato cultivar upon HS. Functional characterization of HSFA7 and HSFB4a in a tolerant–sensitive cultivar pair by virus-induced gene silencing (VIGS)-based silencing and transient overexpression established them as a positive and a negative regulator of HS tolerance, respectively. Promoter:GUS reporter assays and promoter sequence analyses suggest heat-mediated transcriptional control of both the HSF genes in the contrasting cultivars. Moreover, degradome data highlighted HSFB4a is a probable target of microRNA Sly-miR4200. Transient in-planta Sly-MIR4200-effector:HSFB4a-reporter assays showed miRNA-dependent target down-regulation. Chelation of miRNA by short-tandem-target-mimic of Sly-miR4200 increased target abundance, highlighting a link between Sly-miR4200 and HSFB4a. This miRNA has induced several folds upon HS in the tolerant cultivar where HSFB4a levels are reduced, thus exhibiting the inverse miR:target expression. Thus, we speculate that the alleviation of HSFB4a and increased HSFA7 levels govern thermo-tolerance in the tolerant cultivar by regulating downstream heat stress-responsive genes.Item The sly-miR166-SlyHB module acts as a susceptibility factor during ToLCNDV infection(Springer Nature Publishing AG, 2022) Prasad, Ashish; Sharma, Namisha; Chirom, Oceania; Prasad, ManojTomato leaf curl New Delhi virus (ToLCNDV) is a devastating pathogen that causes huge crop loss. It is spreading to new geographical locations at a very rapid rate-raising serious concerns. Evolution of insecticidal resistance in Bemisia tabaci which acts as the carrier for ToLCNDV has made insect control very difficult in the recent years. Thus, it is important that the host molecular mechanisms associated with ToLCNDV resistance/susceptibility are investigated to develop management strategies. In our study, we have identified that sly-miR166/SlyHB module acts as a susceptibility factor to ToLCNDV in Solanum lycopersicum. Sly-miR166 is differentially regulated upon ToLCNDV infection in two contrasting tomato cultivars; H-88-78-1 (tolerant to ToLCNDV) and Punjab Chhuhara (susceptible to ToLCNDV). Expression analysis of predicted sly-miR166 targets revealed that the expression of SlyHB is negatively correlated with its corresponding miRNA. Virus-induced gene silencing of SlyHB in the susceptible tomato cultivar resulted in the decrease in disease severity suggesting that SlyHB is a negative regulator of plant defence. In summary, our study highlights a miRNA/target module that acts as a susceptibility factor during ToLCNDV infection. To the best of our knowledge, this is the first report that highlights the role of sly-miR166/SlyHB module in ToLCNDV pathogenesis.Item Spodoptera litura-mediated chemical defense is differentially modulated in older and younger systemic leaves of Solanum lycopersicum(Springer Nature, 2018) Kundu, Anish; Mishra, Shruti; Vadassery, JyothilakshmiMain conclusion: Metabolite profling, biochemical assays, and transcript analysis revealed diferential modulation of specifc induced defense responses in local, older, and younger systemic leaves in Solanum lycopersicum upon Spodoptera litura herbivory. Plants reconfgure their metabolome upon herbivory to induce production of defense metabolites involved in both direct and indirect defenses against insect herbivores. Herbivory mediated leaf-to-leaf systemic induction pattern of primary and nonvolatile secondary metabolites is not well studied in tomato. Here, we show that, in cultivated tomato Solanum lycopersicum herbivory by generalist insect, Spodoptera litura results in diferential alteration of primary metabolites, majorly sugars and amino acids and specifc secondary metabolites in local, younger, and older systemic leaves. Cluster analysis of 55 metabolites identifed by GC–MS showed correlation between local and younger systemic leaves. Re-allocation of primary metabolites like glucose and amino acids from the local to systemic leaf was observed. Secondary metabolites chlorogenic acid, cafeic acid, and catechin were signifcantly induced during herbivory in systemic leaves. Among specifc secondary metabolites, chlorogenic acid and catechin signifcantly inhibits S. litura larval growth in all stages. Local leaf exhibited increased lignin accumulation upon herbivory. Diferential alteration of induced defense responses like reactive oxygen species, polyphenol oxidase activity, proteinase inhibitor, cell wall metabolites, and lignin accumulation was observed in systemic leaves. The metabolite alteration also resulted in increased defense in systemic leaves. Thus, comparative analysis of metabolites in local and systemic leaves of tomato revealed a constant re-allocation of primary metabolites to systemic leaves and diferential induction of secondary metabolites and induced defenses upon herbivory.Item Genome-wide sequence variations between wild and cultivated tomato species revisited by whole genome sequence mapping(BioMed Central Ltd, 2017) Sahu, Kamlesh Kumar; Chattopadhyay, DebasisBACKGROUND: Cultivated tomato (Solanum lycopersicum L.) is the second most important vegetable crop after potato and a member of thirteen interfertile species of Solanum genus. Domestication and continuous selection for desirable traits made cultivated tomato species susceptible to many stresses as compared to the wild species. In this study, we analyzed and compared the genomes of wild and cultivated tomato accessions to identify the genomic regions that encountered changes during domestication. RESULTS: Analysis was based on SNP and InDel mining of twentynine accessions of twelve wild tomato species and forty accessions of cultivated tomato. Percentage of common SNPs among the accessions within a species corresponded with the reproductive behavior of the species. SNP profiles of the wild tomato species within a phylogenetic subsection varied with their geographical distribution. Interestingly, the ratio of genic SNP to total SNPs increased with phylogenetic distance of the wild tomato species from the domesticated species, suggesting that variations in gene-coding region play a major role in speciation. We retrieved 2439 physical positions in 1594 genes including 32 resistance related genes where all the wild accessions possessed a common wild variant allele different from all the cultivated accessions studied. Tajima's D analysis predicted a very strong purifying selection associated with domestication in nearly 1% of its genome, half of which is contributed by chromosome 11. This genomic region with a low Tajima's D value hosts a variety of genes associated with important agronomic trait such as, fruit size, tiller number and wax deposition. CONCLUSION: Our analysis revealed a broad-spectrum genetic base in wild tomato species and erosion of that in cultivated tomato due to recurrent selection for agronomically important traits. Identification of the common wild variant alleles and the genomic regions undergoing purifying selection during cultivation would facilitate future breeding program by introgression from wild species.Item The α-crystallin domain containing genes: identification, phylogeny and expression profiling in abiotic stress, phytohormone response and development in tomato (Solanum lycopersicum)(Frontiers Media S.A., 2016) Paul, Asosii; Rao, Sombir; Mathur, SaloniThe α-crystallin domain (ACD) is an ancient domain conserved among all kingdoms. Plant ACD proteins have roles in abiotic stresses, transcriptional regulation, inhibiting virus movement, and DNA demethylation. An exhaustive in-silico analysis using Hidden Markov Model-based conserved motif search of the tomato proteome yielded a total of 50 ACD proteins that belonged to four groups, sub-divided further into 18 classes. One of these groups belongs to the small heat shock protein (sHSP) class of proteins, molecular chaperones implicated in heat tolerance. Both tandem and segmental duplication events appear to have shaped the expansion of this gene family with purifying selection being the primary driving force for evolution. The expression profiling of the Acd genes in two different heat stress regimes suggested that their transcripts are differentially regulated with roles in acclimation and adaptive response during recovery. The co-expression of various genes in response to different abiotic stresses (heat, low temperature, dehydration, salinity, and oxidative stress) and phytohormones (abscisic acid and salicylic acid) suggested possible cross-talk between various members to combat a myriad of stresses. Further, several genes were highly expressed in fruit, root, and flower tissues as compared to leaf signifying their importance in plant development too. Evaluation of the expression of this gene family in field grown tissues highlighted the prominent role they have in providing thermo-tolerance during daily temperature variations. The function of three putative sHSPs was established as holdase chaperones as evidenced by protection to malate-dehydrogenase against heat induced protein-aggregation. This study provides insights into the characterization of the Acd genes in tomato and forms the basis for further functional validation in-planta.Item Fruit ripening mutants reveal cell metabolism and redox state during ripening(Springer, 2016) Kumar, Vinay; Irfan, Mohammad; Ghosh, Sumit; Chakraborty, Niranjan; Chakraborty, Subhra; Datta, AsisRipening which leads to fruit senescence is an inimitable process characterized by vivid changes in color, texture, flavor, and aroma of the fleshy fruits. Our understanding of the mechanisms underlying the regulation of fruit ripening and senescence is far from complete. Molecular and biochemical studies on tomato (Solanum lycopersicum) ripening mutants such as ripening inhibitor (rin), nonripening (nor), and never ripe (Nr) have been useful in our understanding of fruit development and ripening. The MADS-box transcription factor RIN, a global regulator of fruit ripening, is vital for the broad aspects of ripening, in both ethylene-dependent and independent manners. Here, we have carried out microarray analysis to study the expression profiles of tomato genes during ripening of wild type and rin mutant fruits. Analysis of the differentially expressed genes revealed the role of RIN in regulation of several molecular and biochemical events during fruit ripening including fruit specialized metabolism and cellular redox state. The role of reactive oxygen species (ROS) during fruit ripening and senescence was further examined by determining the changes in ROS level during ripening of wild type and mutant fruits and by analyzing expression profiles of the genes involved in maintaining cellular redox state. Taken together, our findings suggest an important role of ROS during fruit ripening and senescence, and therefore, modulation of ROS level during ripening could be useful in achieving desired fruit quality.Item Light-induced indeterminacy alters shade avoiding tomato leaf morphology(American Society of Plant Biologists, 2015) Chitwood, Daniel H.; Kumar, Ravi; Ranjan, Aashish; Pelletier, Julie M.; Townsley, Brad T.; Ichihashi, Yasunori; Martinez, Ciera C.; Zumstein, Kristina; Harada, John J.; Maloof, Julin N.; Sinha, Neelima R.Plants sense the foliar shade of competitors and alter their developmental programs through the shade-avoidance response. Internode and petiole elongation, and changes in overall leaf area and leaf mass per area, are the stereotypical architectural responses to foliar shade in the shoot. However, changes in leaf shape and complexity in response to shade remain incompletely, and qualitatively, described. Using a meta-analysis of more than 18,000 previously published leaflet outlines, we demonstrate that shade avoidance alters leaf shape in domesticated tomato (Solanum lycopersicum) and wild relatives. The effects of shade avoidance on leaf shape are subtle with respect to individual traits but are combinatorially strong. We then seek to describe the developmental origins of shade-induced changes in leaf shape by swapping plants between light treatments. Leaf size is light responsive late into development, but patterning events, such as stomatal index, are irrevocably specified earlier. Observing that shade induces increases in shoot apical meristem size, we then describe gene expression changes in early leaf primordia and the meristem using laser microdissection. We find that in leaf primordia, shade avoidance is not mediated through canonical pathways described in mature organs but rather through the expression of KNOTTED1-LIKE HOMEOBOX and other indeterminacy genes, altering known developmental pathways responsible for patterning leaf shape. We also demonstrate that shade-induced changes in leaf primordium gene expression largely do not overlap with those found in successively initiated leaf primordia, providing evidence against classic hypotheses that shaded leaf morphology results from the prolonged production of juvenile leaf types.Item The tomato genome sequence provides insights into fleshy fruit evolution(NPG, 2012) The Tomato Genome Consortium; Sato, Shusei; Zamir, Dani; Giuliano, Giovanni; Tyagi, Akhilesh K.; Chattopadhyay, Debasis; et al.Tomato (Solanum lycopersicum) is a major crop plant and a model system for fruit development. Solanum is one of the largest angiosperm genera and includes annual and perennial plants from diverse habitats. Here we present a high-quality genome sequence of domesticated tomato, a draft sequence of its closest wild relative, Solanum pimpinellifolium, and compare them to each other and to the potato genome (Solanum tuberosum). The two tomato genomes show only 0.6% nucleotide divergence and signs of recent admixture, but show more than 8% divergence from potato, with nine large and several smaller inversions. In contrast to Arabidopsis, but similar to soybean, tomato and potato small RNAs map predominantly to gene-rich chromosomal regions, including gene promoters. The Solanum lineage has experienced two consecutive genome triplications: one that is ancient and shared with rosids, and a more recent one. These triplications set the stage for the neofunctionalization of genes controlling fruit characteristics, such as colour and fleshiness.Item The tomato sequencing project, the first cornerstone of the international Solanaceae project (SOL)(Wiley-Blackwell, 2005) Mueller, Lukas A.; Tanksley, Steven D.; Giovannoni, Jim J.; Eck, Joyce van; Stack, Stephen; Choi, Doil; Kim, Byung Dong; Chen, Mingsheng; Cheng, Zhukuan; Li, Chuanyou; Ling, Hongqing; Xue, Yongbiao; Seymour, Graham; Bishop, Gerard; Bryan, Glenn; Sharma, Rameshwar; Khurana, Jitendra; Tyagi, Akhilesh K.; Chattopadhyay, Debasis; Singh, Nagendra K.; Stiekema, Willem; Lindhout, P.; Jesse, Taco; Lankhorst, Rene Klein; Bouzayen, Mondher; Shibata, Daisuke; Tabata, Satoshi; Granell, Antonio; Botella, Miguel A.; Giuliano, Giovanni; Frusciante, Luigi; Causse, Mathilde; Zamir, DaniThe genome of tomato (Solanum lycopersicum) is being sequenced by an international consortium of 10 countries (Korea, China, the United Kingdom, India, The Netherlands, France, Japan, Spain, Italy and the United States) as part of a larger initiative called the ‘International Solanaceae Genome Project (SOL): Systems Approach to Diversity and Adaptation’. The goal of this grassroots initiative, launched in November 2003, is to establish a network of information, resources and scientists to ultimately tackle two of the most significant questions in plant biology and agriculture: (1) How can a common set of genes/proteins give rise to a wide range of morphologically and ecologically distinct organisms that occupy our planet? (2) How can a deeper understanding of the genetic basis of plant diversity be harnessed to better meet the needs of society in an environmentally friendly and sustainable manner? The Solanaceae and closely related species such as coffee, which are included in the scope of the SOL project, are ideally suited to address both of these questions. The first step of the SOL project is to use an ordered BAC approach to generate a high quality sequence for the euchromatic portions of the tomato as a reference for the Solanaceae. Due to the high level of macro and micro-synteny in the Solanaceae the BAC-by-BAC tomato sequence will form the framework for shotgun sequencing of other species. The starting point for sequencing the genome is BACs anchored to the genetic map by overgo hybridization and AFLP technology. The overgos are derived from approximately 1500 markers from the tomato high density F2-2000 genetic map (http://sgn.cornell.edu/). These seed BACs will be used as anchors from which to radiate the tiling path using BAC end sequence data. Annotation will be performed according to SOL project guidelines. All the information generated under the SOL umbrella will be made available in a comprehensive website. The information will be interlinked with the ultimate goal that the comparative biology of the Solanaceae — and beyond — achieves a context that will facilitate a systems biology approach.