OsPIP2-1 positively regulates rice seed germination by modulating OsAmy3C and α-amylase expression

As timely germination of seeds is crucial to crop yield and quality, the low germination percentage for direct seeding in rice and preharvest sprouting during the late stage of maturity have extremely adverse effects on rice production. Herein, we found that an aquaporin gene OsPIP2-1 was significantly expressed during rice seed germination. The OsPIP2-1 overexpression seeds showed a higher germination rate, while the knockout lines showed a delayed germination phenotype, indicating that this gene positively regulates seed germination. Furthermore, in seeds of OsPIP2-1 overexpression and knockout lines, the activity of α-amylase and the expression of its encoding genes, OsAmy1C and OsAmy1E, were respectively enhanced and suppressed. When OsAmy3C was knocked out in the OsPIP2-1 overexpression lines, seed germination was significantly inhibited. Also, the germination of seeds with OsAmy3C knocked out in the wild-type background was delayed, and the expression level of OsPIP2-1 in these seeds remained almost unchanged during germination, suggesting that OsPIP2-1 is upstream of OsAmy1C. In addition, the ABA-biosynthesis genes OsNCED2/3 were reduced in OsPIP2-1 overexpression lines but raised in knockouts, while the ABA-catabolism gene OsABA8ox1-3 exhibited the opposite trend. Moreover, we have also applied nanosilver, a potential inhibitor of aquaporins, which effectively delays rice seed germination. At the molecular level, the expression of OsPIP2-1 in transcriptional and translational levels was significantly decreased by AgNPs. Meanwhile, the expression of α-amylase and its gene expression were also inhibited by AgNPs. In conclusion, OsPIP2-1 positively regulates rice seed germination by regulating OsAmy3C and α-amylase. It can enhance seed germination vigor in direct-seeded rice cultivation. Nanosilver delays germination by affecting OsPIP2-1 and α-amylase, thus offering a potential strategy for preventing preharvest sprouting.