Tyrosine phosphorylation mediates starch metabolism in guard cell of Vicia faba
2015
Qin, Xiao-Mei | Bian, Ming-Di | Yang, Zhen-Ming | Shi, Wu-Liang
Protein tyrosine phosphorylation plays a central role in many signaling pathways leading to cell growth and differentiation in animals. However, the cellular roles for tyrosine phosphorylation in plant remain unclear. Here we describe that tyrosine phosphorylation involved in stomata closing pathway. Genistein, an inhibitor of protein tyrosine kinases (PTKs), could prevent darkness and abscisic acid (ABA)-induced stomatal closure of Vicia faba L. Stomatal closure induced by high external Ca²⁺ was prevented by phenylarsine oxide (PAO), a specific inhibitor of protein tyrosine phosphatases (PTPs), which promoted closed stomata reopening. Using anti-phosphotyrosine antibody, we detected the distribution of phosphotyrosyl proteins (PYP) by the immuno-fluorescence and immuno-gold electron microscope techniques in guard cells of Vicia faba. It shows that PYP is localized to nucleus, cytoplasm, vacuole and chloroplast of guard cells. Interestingly, the distribution of PYP in chloroplast of guard cell mainly was localized on the surface of starch granule, indicating that there is some relationship between tyrosine phosphorylation and starch metabolism in guard cells. In addition, the starch content in leaves of Vicia faba can be enhanced by inhibiting the activity of PTPs with PAO. Overall, these studies and combined previous report suggest that tyrosine phosphorylation may modulate starch degradation in guard cells, and thus regulating the stomatal movement.
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