Investigating calcium-related tropic responses mediated by PKS2, PUX5 and AtEH2 through quantitative phosphoproteomics analysis of arabidopsis

Abstract

Plants exhibit the ability to detect and respond to external stimuli such as gravity and light. Phototropism refers to the directional growth of plant toward light is instrumentally important for plants growth and development. Gravitropism means that plants’ growth is influenced to gravitational forces by reorienting their organs with respect to the gravity vector directions, such as the shoot stem curving upwards. This research endeavor utilized 4C quantitative phosphoproteomics to explore alterations in protein phosphosites following a 40-second unilateral blue light source and 20-second reorientation of Arabidopsis plants on Earth. Through this study, of the 55 blue light-regulated phosphopeptides identified on transgenic plant PHOT1/phot1pho2, 38 were related to or regulated to light irradiation, whereas 6625 phosphopeptides were identified in gravistimulated Arabidopsis, with quantitative analysis revealing the up-and down-regulation of unique PTM peptide arrays. Notably, proteins associated with cytoskeleton dynamics and plastid movement were among the responsive groups. The investigation highlighted that S239 of Phytochrome kinase substrate2 was most likely a target of PHOT1 supported by all these bioinformatics results and KUP5 has exhibited impair phototropic phenotype in the kup5 T-DNA insertion mutant. On the other hand, among Calcium/Camodulin related phosphosites, up-regulation of AtEH2 phosphorylation is shown in MS and phosphorylation of AtEH2 was found as one key regulator at the beginning of gravity vector alteration, followed by series of immunoblotting validation to study its function in gravitropism. Gravitropic curvature measurement shed the light of the hypothetical mechanism which AtEH2 phosphorylation is involved in the initial signaling of gravity sensing.

Date of Award	2024
Original language	English
Awarding Institution	The Hong Kong University of Science and Technology
Supervisor	Ning LI (Supervisor) & Karl Wah Keung TSIM (Supervisor)