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Exploring the relationship between micro RNAs and heat stress transcription factors in tomato

Student name: Ms Priyanka S
Guide: Dr Ramakrishnan Sitaraman
Year of completion: 2018
Host Organisation: National Institute of Plant Genome Research (NIPGR), New Delhi
Supervisor (Host Organisation): Dr Saloni Mathur
Abstract: To mitigate the adverse effects of heat stress (HS) on crop production, it is imperative to have deep knowledge of the heat-defense-mechanism that has evolved in plants to tide over hyper-thermal stress.Heat stress transcription factors (HSFs) are mediators of signal transduction chain regulating activation of several genes, triggering an intricate transcriptional network. Similarly, microRNAs (miRNAs), small non-coding regulatory molecules regulate various aspects of plant growth and development including stress response.However, knowledge of the interplay of miRNAs:HSFs in regulating HS-response is still elusive; only a handful of heat-responsive miRNAs have been reported in plants, none of which have been functionally validated to target any HSFs. In the present study eleven miRNAs regulating HSFs post-transcriptionally have been identified from degradome data and validated by 5’RLM-RACE and transient assays in Nicotianabenthamiana. HsfB2a was established as miRSM-1 target by transient assay. Expression analysis of HsfB2a and miRSM-1 in leaf and inflorescence tissues confirms its cleavage by miRNASM-1. To further exploring the role of HsfB2a we have performed transactivation assays in yeast confirming HsfB2a as a repressor of transcription. Overexpression analysis in tomato seedlings shows HsfB2a as negative regulator of growth and thermos-tolerance. This study confirms the regulation of tomato HsfB2a by miRNASM-1, this regulatory loop further helps the plant in thermo-tolerance during heat stress.