Research Projects

TCP proteins, an extensive family of plant specific transcription factors (TF), is instrumental in orchestrating a wide range of developmental activities in plants and is broadly divided into two classes I and II, depending on their DNA sequence binding preferences., TCPs were reported to be instrumental in leaf shape maintenance, as suggested from mutational analysis. Specifically, mutation of class II TCP genes, leads to development of curly, crinkly leaf phenotype in plants, symptomatically similar to that when plants were infected with leaf curl viruses. Phytohormone jasmonic acid plays important role in regulating plant immune as well as developmental responses under multiple environmental stimuli and in certain cases its signaling had been found to be regulated by TCP TFs. Jasmonic acid(JA) signaling, as studied earlier was found to deter progression of some leaf curl viruses in plants. Evolutionarily, spatiotemporal regulation of TCP gene expression in plants was found to be under control of microRNA 319(miR319) family. Almost a decade ago, a study pointed out that severe infection of Tomato leaf curl virus(TolCV) in tomato (Solanum lycopersicum) was correlated with high transcript accumulation of miR319. But no further studies envisaged to look into molecular details of consequence of miR319 upregulation in TolCV pathogenesis and plant immune response manipulation. As miR319 targets TCPs, which is pivotal in leaf shape maintenance and immune response regulation via JA signaling, analyzing miR319-TCP-JA interplay in backdrop of TolCV infection would provide an in-depth insight into overall immune-developmental signaling network of tomato. This would be of extreme importance to design antiviral tomato lines in near future. Our preliminary study segregated available 5 different miR319 isoforms into Group-I (Sly-miR319a, b, c-3p) and Group-II (Sly-miR319c-5p, d) based on sequence homology. Out of 30 available TCP TFs in tomato, we found 8 of them (TCP-1,2,3,10,19, 24,29,30) targeted by group-I miR319 isoforms, while group-II doesn’t target any TCPs. We further found Group-I miR319 isoforms are highly upregulated with simultaneous suppression of gene expression of TCP-1,2,3,10,24 in tomato during TolCV infection. Transient overexpression of Sly-miR319a in tomato resulted in increase of TolCV titer, hinting favored viral infection. Further we plan to look into details how different Sly-miR isoforms are boosting TolCV pathogenesis. Their suggested involvement in regulating leaf curling phenotype will also be investigated by both overexpression and STTM based silencing studies. We will study the mechanism of targeted suppression of TCPs by Sly-miR319 isoforms during infection. We will identify specific TCP capable of best transcriptional reprogramming during infection using STTM background and analyze its mechanistic role in leaf shape regulation and antiviral response. Insights from this study will be leveraged to develop specific TCP overexpressing transgenic tomato, which will be exploited for studying in-depth transcriptional reprogramming using RNA seq analysis. Categorizing and interpreting differential gene expression will provide a comprehensive picture about immuno-developmental signaling network, much needed to analyze TCP dependent antiviral strategy. We found distinct suppression of JA biosynthesis (AOS) gene during TolCV infection in preliminary study and identified probable TCP binding site at its promoter. Further we will check whether miR319 is suppressing JA signaling or not and JA itself only can deter TolCV infection. Next, analysis of transcriptome data is expected to hint regulation of JA signaling genes by TCP as part of antiviral response, which will be later validated by EMSA and transactivation assay. Overall this project will reveal the role of TCP in shaping immune response against TolCV and is expected to provide important cues to generate virus resilient tomato lines in near future.