Preliminary Study On The Mechanism Of Overexpression Low Silicon Rice Gene 1 (Lsil) To Enhance Rice UV-B Resisitance

Depletion of stratospheric ozone (O3) due to the emission of chlorofluorocarbons and other trace gases has resulted in increased solar ultraviolet-B radiation on the earth′s surface, which would affect the agricultural production and the growth of plants, and harmful to the food security. Rice is one of the most important food crops, and the yield and quality maybe decreased when it was exposed to UV-B supplement. Therefore, an effective measure to reduce UV-B damage to food crops seems important to the agricultural production. Earlier research has shown that silicon is beneficial to rice growth and helps rice overcome abiotic and biotic stress, such as reduing lodging, increasing resistance to pests and diseases, as well as other stressful conditions. Our preliminary study suggested that silicon contributes to enhance rice UV-B resistance. Rice is a crop with high silicon-accumulation, a NOD-26 transporter encoded by low silicon rice 1 (Lsi1) gene which locates in rice roots uptaking silicate and transporte them from the external environment to the root cells for the plant. Therefore, rice ability to absorb silicate maybe relative to the expression level of Lsi1, and result in contributing to the rice UV-B tolerance. However, the further mechanism is unknown, and indicating the mechanism is helpful for regulating rice UV-B resisitance.In this study, we used a UV-B-sensitive rice accession Dular as the donor material. Base on the open reading frame (ORF) sequence of rice Lsi1, we designed the PCR primers to amplificate rice Lsi1 and inserted it into a gene-overexpression vector namedly Ubiquitin1301 to construct the recombinant plasmid (Lsi1-Ubiquitin1301), and then transformed it into Agrobacterium EHA105; Using Agrobacterium-mediated genetic transformation system, we obtained the Dular's mutants with Lsi1 overexpression in root. The gene expression levels of phenylalanine ammonia-lyase (PAL) and photolyase were detected by semi-quantitative RT-PCR, which showed that both of the genes expression levels were enhanced in Lsi1-overexpression in rice leaves, when compared to the wild type (WT). Enhancing UV-B radiation could activate this function, showing higher physiological effect than that in WT; Whilst the content of secondary metabolites, such as total phenol, total flavonoids etc.which could absorb UV-B radiation were increased, and enhancing UV-B radiation could increase the contents significantly higher than that in WT under UV-B radiation. The results suggested that overexpression of Lsi1 can increase the content of UV-B absorbing compounds and enhance DNA repairing capacity to UV-B damage by enhancing the expression of related genes, which contribute to enhance rice UV-B tolerance.The findings help us breed UV-B resistant rice in breeding with the molecular genetic way.