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Previous studies have demonstrated the possible role of several aquaporins in seed germination. But systematic inves-tigation of the role of aquaporin family members in this process is lacking. Here, the developmental regulation of plasmamembrane intrinsic protein (PIP) expression throughout germination and post-germination processes in rice embryoswas analyzed. The expression patterns of the PIPs suggest these aquaporins play different roles in seed germination andseedling growth. Partial silencing of the water channel genes, OsPIP1;1 and OsPIP1;3, reduced seed germination whileover-expression of OsPIP1;3 promoted seed germination under water-stress conditions. Moreover, spatial expressionanalysis indicates that OsPIP1;3 is expressed predominantly in embryo during seed germination. Our data also revealedthat the nitric oxide (NO) donors, sodium nitroprusside (SNP) and S-nitrosoglutathione (GSNO), promoted seed germi-nation; furthermore, the NO scavenger, 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide, inhibitedgermination and reduced the stimulative effects of SNP and GSNO on rice germination. Exogenous NO stimulated thetranscription of OsPIP1;1, OsPIP1;2, OsPIP1;3 and OsPIP2;8 in germinating seeds. These results suggest that waterchannels play an important role in seed germination, acting, at least partly, in response to the NO signaling pathway.
Previous studies have demonstrated the possible role of several aquaporins in seed germination. But, the developmental regulation of plasmamembrane intrinsic protein (PIP) expression throughout germination and post- The expression patterns of the PIPs suggest these aquaporins play different roles in seed germination and seeding growth. Partial silencing of the water channel genes, OsPIP1; 1 and OsPIP1; 3, reduced seed germination while over-expression of OsPIP1; 3 was expressed predominantly in embryo during seed germination. Our data also shows that the nitric oxide (NO) donors, sodium nitroprusside (SNP) and S-nitrosoglutathione ( GSNO), promoted seed germi-nation; furthermore, the NO scavenger, 2- (4-carboxyphenyl) -4,4,5,5-te tramethylimidazoline-1-oxyl-3-oxide, inhibitedgermination and reduced the stimulative effects of SNP and GSNO on rice germination. Exogenous NO stimulated the transcription of OsPIP1; 1, OsPIP1; 2, OsPIP1; 3 and OsPIP2; 8 in germinating seeds. These results suggest that waterchannels play an important role in seed germination, acting, at least partly, in response to the NO signaling pathway.