Research Projects

Plants are constantly subjected to various stresses, including biotic and abiotic stresses, that affect normal growth, development, and productivity of the plants. Endoplasmic Reticulum (ER) provides an environment for proper folding and post-translational modification of secretory proteins. A condition called ER stress is caused by unfolded or misfolded proteins that accumulate in ER under biotic and abiotic stresses. It sets off a molecular response called Unfolded protein Response (UPR)) to attain ER homeostasis (Walter and Ron, 2011). The UPR is mediated by a conserved signaling network composed of two branches in plants. The first branch consists of Inositol Requiring Enzyme-I and basic leucine zipper60 (IRE1-bZIP60). Upon ER stress, IRE1 splices bZIP60 mRNA, which now encode a protein that move to the nucleus and act as a transcription factor to activate the expression of downstream genes. IRE1 also activate a RIDD pathway degrading many mRNAs there by reducing the protein load and stress in the ER. The second branch involves two ER membrane-associated transcription factors, bZIP17 and bZIP28 (Howell, 2013). These are membrane proteins, but upon moving to the Golgi, under ER stress, they are cleaved by an intramembrane proteolysis and the cytosolic domain is now move to the nucleus and act as a transcription factor. bZIP28/17 and bZIP60 work together or with other co-activators to enhance gene expression., ultimately mitigating ER stress. Upon persistent and prolonged ER stress, UPR cannot re-establish ER homeostasis, resulting in shifting of signaling from pro-survival to pro-death response ultimately leading to the activation of Programmed Cell Death (PCD) pathway. PCD is a fundamental genetically controlled process under the influence of a certain threshold of stress factors that lead to disturbance in the metabolic pathway (Foyer & Noctor, 2005). PCD pathways in animals are relatively well characterized. Even though PCD plays an essential role in many aspects of plant development and stress responses, the underlying molecular mechanisms are poorly understood. The signaling pathways of PCD in animal cells have several pro-apoptotic proteases called caspases, which are crucial in ER stress-induced PCD as well. Plants do not have such caspases but have caspase-like proteases. Vacuolar processing enzymes (VPE), proteasome subunit β1(PBA1), cathepsin, metacaspases, BAX inhibitor and membrane associated transcription factor NAC089 are believed to be involved in ER stress-induced PCD in plants (Simoni et al., 2022). It is not clear what triggers the cell death and also the regulation of the pathway in plants. In animals, IRE1 seems to play a major role in cell fate decisions. The research envisages to understand the switching of pro-survival to pro-death response using tomato model system. To understand pathways leading to a cell death response chemical inducers tunicamycin and dithiothreitol will be used. The concentration of these chemicals will be determined by following/ monitoring cell death inducer genes which are known from other cell death systems in plants (eg: developmental cell death, stress induced cell death). Once these concentrations and time intervals of treatment are determined, the treated cells/ tissues will be subjected to RNA-seq analysis and differential gene expression profile will be analysed. These datasets will be further analyzed to see signatures of cell death pathway for known plant PCD pathways and genes including those used earlier. The information will be used for a comparative analysis of pro-death and pro-survival pathways. Specifically, we will look into communication between organelles, the ER, mitochondria, and the chloroplast. These genes will be tested for their involvement in cell death induced by abiotic stresses like heat. The information gathered will be further experimented with for developing stress-tolerant plants in tomato