Initial characterization of a subgroup of Arabidopsis group VIII receptor-like cytoplasmic kinases in immune and flowering time pathways
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In order to defend against disease, plants have evolved a tightly coordinated signaling network to rapidly prevent the spread of infection. Given the severity of yearly crop loss to pathogen threats, further understanding of how plants defend against pathogens is vital to the improvement of current agricultural strategies. Receptor protein kinases on the plant cell surface recognize microbes and trigger phosphorylation-dependent signaling events, ultimately leading to genetic reprogramming. Receptor-likecytoplasmic kinases are key mediators of immune signal transduction, but many remain largely understudied. This thesis focuses on the group VIII RLCKs in Arabidopsis thaliana, also known as the AtPTI1-like kinases, for which an immune function has not been shown. Using a functional genomics approach, I demonstrate that a subgroup of the group VIII RLCKs regulate flowering time and may additionally function as negative regulators of immunity by mediating the oxidative burst. Additionally, I found that one of these RLCKs, PTI1-1, interacts with the negative regulator of defense CALCIUM - DEPENDENT PROTEIN KINASE 28 (CPK28) and the positive immune regulator BOTRYTIS INDUCED KINASE 1 (BIK1), further suggesting the involvement of these RLCKs in immune signal transduction. Broadly, this work has shown two novel functions for the AtPTI1-like kinase family in both defense and development, and primes future research for this previously uncharacterized group.