Publications of NIPGR Scientists

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Author: search.filters.author.Rao, SombirSubject: search.filters.subject.Heat

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    Deciphering the role of MIR169d:NF-YA2 module under individual as well as combined drought and heat stress in Arabidopsis
    (Springer Nature Publishing AG, 2024) Gupta, Apoorva; Ghosh, Debasish; Rao, Sombir; Mathur, Saloni
    Plants are often subjected to a combination of abiotic stresses under natural environmental conditions. The response of plants to combined stresses can be very diferent from that to the individual stress. Several regulatory mechanisms work in harmony to maintain plant’s homeostasis during stress conditions. Among them the roles of microRNAs (miRNAs) in combined stresses are beginning to be unravelled. In this study, we evaluated the MIR169d: NF-YA2 target module in individual as well as combined drought and heat stress (HS) in Arabidopsis. We found that MIR169d is highly HS inducible, however, contrary to the reported downregulation of MIR169a/c forms in drought stress in literature, MIR169d is upregulated in drought. Moreover, while MIR169d expression is upregulated during combined stress, the response is less than individual stresses. Further, Arabidopsis plants overexpressing MIR169d or target nf-ya2 knockout mutant plants are more tolerant to both individual as well as combined heat and drought stress as indicated by the higher expression of stress responsive genes and less Trypan blue staining, while plants overexpressing NF-YA2 or those in which miR169defg isoform is sponged up (MIM169defg) are more prone to individual as well as combined heat and drought stress. The MIR169d promoter harbours both heat and drought stress-responsive cis-elements. Assessment of GUS expression in MIR169d-promoter:GUS and NF-YA2-promoter:GUS transgenic lines shows increased and reduced reporter expression in all the three stress conditions as compared to control, respectively. This suggests a stress-induced transcriptional regulation of the MIR169d:NF-YA2 pair. Thus, the MIR169d:NF-YA2 module can be potentially exploited to engineer crops for resistance to multiple abiotic stresses.
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    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, Saloni
    Heat 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.
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    Characterization of novel regulators for heat stress tolerance in tomato from Indian sub-continent
    (John Wiley & Sons, 2020) Balyan, Sonia; Rao, Sombir; Jha, Sarita; Bansal, Chandni; Das, Jaishri Rubina; Mathur, Saloni
    The footprint of tomato cultivation, a cool region crop that exhibits heat stress (HS) sensitivity, is increasing in the tropics/sub‐tropics. Knowledge of novel regulatory hot‐spots from varieties growing in the Indian sub‐continent climatic zones could be vital for developing HS‐resilient crops. Comparative transcriptome‐wide signatures of a tolerant (CLN1621L) and sensitive (CA4) cultivar‐pair shortlisted from a pool of varieties exhibiting variable thermo‐sensitivity using physiological, survival and yield‐related traits revealed redundant to cultivar‐specific HS‐regulation. The antagonistically‐expressing genes encode enzymes and proteins that have roles in plant defense and abiotic stresses. Functional characterization of three antagonistic genes by overexpression and silencing established Solyc09g014280 (Acylsugar acyltransferase) and Solyc07g056570 (Notabilis), that are up‐regulated in tolerant cultivar, as positive regulators of HS‐tolerance and Solyc03g020030 (Pin‐II proteinase inhibitor), that is down‐regulated in CLN1621L, as negative regulator of thermotolerance. Transcriptional assessment of promoters of these genes by SNPs in stress‐responsive cis‐elements and promoter swapping experiments in opposite cultivar background showed inherent cultivar‐specific orchestration of transcription factors in regulating transcription. Moreover, overexpression of three ethylene response transcription factors (ERF.C1/F4/F5) also improved HS‐tolerance in tomato. This study identifies several novel HS‐tolerance genes and provides proof of their utility in tomato thermotolerance.