Suppression and overexpression of Lsi1 induce differential gene expression in rice under ultraviolet radiation

Low silicon rice gene 1 (Lsi1) belongs to a member of Nod26-like major intrinsic protein (NIP) subfamily and is thought to control silicon (Si) accumulation in rice. In order to further elucidate its regulatory mechanisms in the defense of rice plants to enhanced ultraviolet-B (UV-B) radiation stress, Lsi1 was subjected to suppressed and overexpressed treatments in a UV-B tolerance rice accession Lemont as well as to overexpressed treatment in a UV-B sensitive rice accession Dular. The results showed that transcript levels of Lsi1 increased in Lsi1-overexpressed transgenic lines of rice accessions Lemont and Dular, but down-regulated in Lsi1-RNAi transgenic line of Lemont in comparison with their wild types (WT). A similar tendency was found in the root Si uptake and the Si concentrations in leaves. Further, the different transgenic rice lines and their WT were exposed to enhance UV-B radiation, study by suppression subtractive hybridization (SSH) found that Lsi1 not only could regulate the expression of phenylalanine ammonia-lyase (PAL), 4-coumarate-CoA ligase (4CL) and photolyase (PL), but also could induce other signal transduction-, detoxification-, resistance-, and photosynthesis-related genes. The findings suggested that the regulation of silicon nutrient by enhancing/inhibiting expression of Lsi1 could effectively induce the transcription of the mRNAs relative to tolerance in rice.