Abstract
Plasma membrane aquaporin, PIP2 subfamily is considered to be regulated by protein phosphorylation. Putative phosphorylation residues, Ser115 and Ser280, in pear PcPIP2;2 were mutated to Ala (this mimics non-phosphorylated state) or Asp (this mimics phosphorylated state) and water transport activity of these mutants were measured in Xenopus oocytes. Water transport of PcPIP2;2s having only one mutation from Ser to Ala was almost the same as that of WT PcPIP2;2. By contrast, PcPIP2;2 mutant, whose Ser115 and Ser280 were mutated to Ala, showed lower water transport activity. There is no report telling Ser115 phophorylatinon in planta, although Ser280 phophorylatinon have been reported. This means that Ser115 is not phophorylated in planta or it,s phophorylation level is quite low, suggesting the importance of Ser280 phosphorylated state. Therefore we prepared phosphor-specific antibody against Ser280. Western blot showed that phosphorylated state of PcPIP2;2 accorded with diurnal growth of pear fruits.
