Cloning And Anaylsis Of Two Oryza Sativa Protein Repair L-isoaspartyl Methyltransferases

It is well known that,rice,one of the most important grain crops in the world,feeds almost half of the population worldwide.China is the world's largest producer and consumer of rice;therefore,stable production of rice is the fundamental guarantee of national food security,and of great significance.However,rice production is facing many challenges in China,such as large-scale input of chemical fertilizers with low utilization efficiency and rice grain deterioration caused by improper storage.The PIMT in plants is considered to be associated with seed vigor and storability;however,to date,there is no research focusing on PIMT in rice.In this study,two candidate PIMT genes were successfully cloned from rice,and their preliminary functions were identified through a series of bioinformatics analysis and molecular biology assays.Finally,Plant materials with differential expressions of OsPIMTs were generated through genetic transformation as well as mutant screening,to further explore their biological functions in seed storability and under low nitrogen stress.The main results are as follows:1.In this study,the full-length cDNA sequences of two rice PIMT genes,referred as to OsPIMT1 and OsPIMT2,were cloned using Smarter RACE.Similarities and differences in structure and function between two genes,OsPIMT1 and OsPIMT2,and previously cloned PIMTs were analyzed using bioinformatics.Characteristics of two genes were summarized,which laid the foundation for subsequent research..2.Through analysis of expression patterns OsPIMTs,the results showed that OsPIMTs were induced by adversity stress to different extent,and also upregulated by the ABA treatment.Meanwhile,they exhibited different expression patterns in various tissues,in which OsPIMT2 was mainly in green tissues,and able to localize in chloroplast,while OsPIMT1 was universal in tissues,and existed mainly in the cytoplasm.For nutrient deficiency stress,the candidate gene elf4a was screened out as reference gene.OsPIMTs were found to be most sensitive to nitrogen deficiency stress in a short period exposure to nutrient deficiency,although displaying a broad up-regulation by a long period exposure to nutrient deficiency.3.The artificial aging of homozygous 4ZH mutant and wild-type Zhonghua 11 were carried out,and the result showed that 4ZH conferred lower germination rate than wild-type,indicating that 4ZH is more sensitive to artificial aging.Analysis of transgenic plants under low-nitrogen stress,showed that compared with wild-type,overexpression transgenic plants exhibits lower lipid peroxidation level and higher biomass.