Nano-silver and forskolin regulate rice seed germination mediated by OsPIP2-1 and α-amylase

As timely germination of seeds is crucial to crop yield and quality, the low germination percentage for direct seeding in rice and pre-harvest sprouting during late stage of maturity have extremely adverse effects on rice production. Herein, we found that nano-silver inhibited rice seed germination while forskolin promoted this process. Germination assay showed that 20 M AgNPs and 0.5 M forskolin could be the optimal concentrations regulating rice seed germination. At the molecular level, an aquaporin gene, OsPIP2-1, was most highly expressed among those homologous genes during rice seed germination, and was decreased by AgNPs and increased by forskolin. Meanwhile, the activity of -amylase and its genes expression were also inhibited by AgNPs and promoted by forskolin. Next, the germination percentage of OsPIP2-1 overexpressing seeds was significantly higher than that of wild-type, and that of OsPIP2-1 knockout seeds was dramatically reduced. Furthermore, compared with the wild type, -amylase activity and the transcription of OsAmy3C and OsAmy3E were increased in OsPIP2-1 overexpressing seeds and decreased in OsPIP2-1 knockout seeds, indicating that OsPIP2-1 positively regulates -amylase. Interestingly, seed germination, -amylase activity and its genes expression in OsPIP2-1 overexpressed and knockdout lines could also be inhibited by nano-silver and promoted by forskolin. In conclusion, we propose that nano-silver and forskolin regulated seed germination by modulating the expression of OsPIP2-1 and thus -amylase. Our results may bring new application of nano-silver and forskolin in rice cultivation.