Study On The Molecular Physiological Mechanism Of Lsi1 Mediated Rice Defense To UV-B Stress

Silicon plays an important role to enhance the capacity of rice resistance to stress,and it is absorbed into the rice basing on NOD26,which is an aquaporins encoded by low silicon gene 1(Lsil).In this study,Lsil overexpression transgenic Lemont,Lsil RNA interference transgenic Lemont,Lsil overexpression transgenic Dular and their wild types(WT)were used as donor plants.First of all,Tail-PCR was conducted to detect the insertion site of the transgenic vector in transgenic rice plants,the results showed that genetic transformation did not disrupt other function genes.On this basis,comparison of the silicon content among these rice lines showed that the silicon content was increased significantly in Lsi1-overexpressed rice,however,the silicon content was significantly reduced in Lsi1-RNAi rice,when compared to that of WT.Observation by scanning electron microscope also found that more silicas was deposited in Lsi1-overexpression transgenic rice leaf than the wild type.Further,change of the activity of ascorbic acid peroxidase(APX),superoxide dismutase(SOD),peroxidase(POD)and phenylalnine ammonialyase(PAL)and the content of malondialdehyde(MDA)and proline(Pro),total polyphenols,flavonoids in different transgenic rice plants and their wild type plants were also studied,the results showed that the enzyme activity of APX,SOD,POD,PAL was significantly improved in the Lsi1-overexpression rice leaf,and the contents of Pro,total phenol and flavonoids were significantly increased,but the content of MDA was decreased significantly,of which are helpful to improve rice resistance;however,the reverse as true in that of Lsi1-RNAi transgenic rice.Enhancing on UV-B radiation resulted in increased enzyme activity,Pro,total phenol and flavonoids content and decreased MDA contents in each rice,but the Lsi1-overexpression transgenic rice still presented highest enzyme activity,Pro,total phenol and flavonoids content and lowest MDA content,all of which contribute to enhance rice UV-B resistance,but in contrast to this,Lsi1-RNAi transgenic rice was shown weakest in UV-B resistance.Among the enzymes,PAL is an important enzyme which can control the synthesis of secondary metabolites such as the total phenol and flavonoids.The gene encoding PAL is a multigene family which contains 11 gene members.Quantitative PCR(qPCR)was then used to detect the different expression level of the 11 gene members,it was found that PAL8 could be positively regulated by Lsil,according to compare the changes gene expression levels of the 11 members,the results suggested that Lsil regulates the synthesis of the substances such as total phenol and flavonoids by up-regulating the gene expression level of PAL8.In addition,comparative proteomics from Lsi1-overexpression,Lsi1-RNAi and WT under UV-B radiation showed that Lsi1 can also comprehensively enhance rice resistance to UV-B stress through control the defence-relative proteins such as germin-like protein 8-14,L-ascorbate peroxidase 2 in cytosolic,Phosphoglycerate kinase,chaperone Os06g0114000 protein,chlorophyll a/b-binding protein.