Dissecting Calcium Homeostasis in Arabidopsis thaliana: Roles in Temperature Response and Immune Signaling

Calcium (Ca²⁺) is an essential secondary messenger for plant signal transduction. Plants typically maintain a low concentration of cytosolic Ca²⁺ ([Ca²⁺]cyt), allowing for a rapid increase in [Ca²⁺]cyt in response to environmental stimuli. [Ca²⁺]cyt is maintained through the function of different Ca²⁺ transporters including autoinhibited Ca²⁺ ATPases (ACAs) and Ca²⁺/H⁺ antiporters (CAXs), which are localized to various subcellular compartments. Prior studies have uncovered the physiological effects of elevated [Ca²⁺]cyt, while little is known about those of reduced [Ca²⁺]cyt. To address this gap, we generated Arabidopsis lines overexpressing tonoplast-localized CAX3 to lower [Ca²⁺]cyt, allowing us to investigate the impacts of reduced [Ca²⁺]cyt on temperature tolerance. In this study, we found that overexpressing CAX3 improves plants’ heat tolerance but increases plants’ susceptibility to chilling stress. To further understand the mechanisms underlying [Ca²⁺]cyt regulation, we also examined the interaction of ACA8/10 and salicylic acid (SA)-immune pathway. Specifically, we tested the genetic interaction between ACA8/10 and two genes of interest involved in SA signaling or biosynthesis, CBP60g and SID2. We generated aca8 aca10 cbp60g and aca8 aca10 sid2 triple mutants, and compared the phenotypes of the triple mutants with that of the aca8 aca10 double mutants and the corresponding cbp60g or sid2 single mutants. Preliminary phenotyping data suggests that SID2 mediates the autoimmune phenotype of aca8 aca10, and future experiments will be needed to confirm this relationship.

My summer BTI internship has been an invaluable experience. Over the past six weeks, I have gained first-hand experience on how plant research is carried out in a lab. Not only have I learned a number of lab techniques, I have also been exposed to a variety of professional skills. Whether it was proposing and summarizing a research project or performing PCR and gel electrophoresis, I appreciated each step of the research process. I also really enjoyed learning about all the diverse research going on at BTI through the weekly Wednesday seminars. Seeing how passionate each speaker was about their research was truly inspiring. One of the most valuable skills I learned through participating in this program is how to think critically and respond to setbacks. This internship has taught me that science is not always linear, and that I should approach questions and analyze results with an open mind. The skills that I have learned in this program will definitely follow me in my future research endeavors. I would like to thank my mentor Peiqiao Xie, Dr. Jian Hua, the Hua Lab, and BTI for providing me with this incredible opportunity.