1. ¹Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, 300 Fenglin Road, Shanghai 200032, China
2. ²Korea Research Institute of Bioscience and Biotechnology, Oun-dong 52, Yusong, Taejon 305-333, South Korea

Correspondence: Wei-Ai Su, Tel: +86-21-54924247; Fax: +86-21-54924015 E-mail: zstressc@online.sh.cn

Received 31 October 2006; Revised 10 January 2007; Accepted 25 January 2007.

Abstract

Previous studies have demonstrated the possible role of several aquaporins in seed germination. But systematic investigation of the role of aquaporin family members in this process is lacking. Here, the developmental regulation of plasma membrane intrinsic protein (PIP) expression throughout germination and post-germination processes in rice embryos was analyzed. The expression patterns of the PIPs suggest these aquaporins play different roles in seed germination and seedling growth. Partial silencing of the water channel genes, OsPIP1;1 and OsPIP1;3, reduced seed germination while over-expression of OsPIP1;3 promoted seed germination under water-stress conditions. Moreover, spatial expression analysis indicates that OsPIP1;3 is expressed predominantly in embryo during seed germination. Our data also revealed that the nitric oxide (NO) donors, sodium nitroprusside (SNP) and S-nitrosoglutathione (GSNO), promoted seed germination; furthermore, the NO scavenger, 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide, inhibited germination 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 water channels play an important role in seed germination, acting, at least partly, in response to the NO signaling pathway.