Physiological Studies on Pseudo-Histidine Phosphotransfer Protein 3 (OsPHP3) in Rice
Date Issued
2016
Date
2016
Author(s)
LEE, CHIA-YUN
Abstract
Cytokinins are phytohormones that play important roles in plant development and stress tolerance. Cytokinin signaling involves a multiple two-component signaling system. Histidine phosphotransfer proteins (HP) mediate the transfer of phosphoryl groups from membrane-bound receptor, histidine kinases (HK), to response regulators (RR) that trigger the downstream responses. It has been shown that Arabidopsis histidine phosphotransfer protein 6 (AHP6) which lacks the conserved His residue acts as a cytokinin negative regulator. Oryza sativa pseudo-histidine phosphotransfer protein (OsPHP) also lacks the conserved His residue required for phosphotransfer that is found in authentic-HPs. However, studies on the functions of OsPHPs remain limited. In this study, the gene expression and the alternative splicing of OsPHP3 were characterized. OsPHP3 has three alternative splicing variants. The gene expression and the alternative splicing of OsPHP3 are tissue-specifically expressed. RT-PCR analysis indicates that the expression level of OsPHP3.1 is higher than that of OsPHP3.2/ OsPHP3.3 in most tissues. The root tip is the only tissue where the expression level of OsPHP3.2/ OsPHP3.3 is higher than that of OsPHP3.1. The gene expression and the alternative splicing of OsPHP3 are also regulated by dark, cytokinin, auxin, salt and drought. In Osphp3-deficient and OsPHP3-overexpression plants, OsPHP3 negatively regulates root growth and decreases the cytokinin sensitivity which can be reflected in chlorophyll rentention, and shoot callus regeneration experiments. In addition, OsPHP3 enhances survival rate under heat treatment but decreases survival rate under salt treatment. These results indicate that OsPHP3 is a negative regulator of rice cytokinin signaling and plays different roles in heat and salt tolerance in rice.
Subjects
Oryza sativa pseudo-histidine phosphotransfer protein
cytokinin signaling
alternative splicing
abiotic stress
Type
thesis
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