Date of Award

12-20-2021

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Biology

First Advisor

Mariya Khodakovskaya

Abstract

Calcium ion plays a significant role in plant signal transduction pathways, including regulation of stress-induced gene expression. Sensor proteins such as proteins with calcium-binding C2 domains can perceive changes in cellular calcium level. Functional analysis of such sensor proteins will give us a better understanding of plant stress signaling. Synaptotagmins are a group of proteins containing C2 domains that are capable of binding calcium ions and regulate gene expression in response to external abiotic stress stimuli. Here, we used a reverse genetic approach to analyze the function of synaptotagmin – 4, which is one of the five identified synaptotagmin proteins in Arabidopsis thaliana. The T-DNA insertion knockout mutants for Arabidopsis' Syt4 gene showed enhanced tolerance to drought stress and increased sensitivity to salt stress. The syt4 mutant lines of Arabidopsis thaliana exhibited a slower rate of water consumption and increased levels of ABA in the leaves, showing an increase in overall growth efficiency under water deficit conditions. On the other hand, the syt4 mutant lines were sensitive to increased levels of salt in the growth media, showing slower rate of germination and inhibition of root growth under salt stress. Therefore, we can say that the synaptotagmin-4 protein works as a negative regulator of drought stress response and a positive regulator of salt stress response in Arabidopsis thaliana.

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