The Mechanism Of OsPIMT1 Gene Affecting Seeds Vigor From Rice (Oryza Sativa.L)

Rice is one of the most important staple food crops in the world.Its stable production is the fundamental guarantee for national food security.Deterioration and loss of viability of rice grains during storage make a great impact on national food security and food safety.Previous researches showed that the protein L-isoaspartyl Methyltransferase(PIMT)is related to maintaining seed vigor and longevity.Overexpression of PIMT in seeds could repair the abnormal isoAsp into normal Asp,thus increasing seed viability during aging,and suppression of PIMT1 caused accumulation of isoAsp which lead to accelerated loss of seed vigor.In our previous work,we have isolated two PIMT genes from rice(Oryza sativa L.),i.e.OsPIMT1 and OsPIMT2.Transgenic lines with differential expressions of OsPIMT1 were obtained as well as mutant screened.In order to understand the mechanism of OsPIMT1 for seed vigor and storability,The corresponding research was performed and the main results are as follows:1.The OsPIMT1 gene of cultivated rice and wild rice was cloned and analyzed.The sequences of OsPIMT1 gene from different varieties.were some differences,most of which were located in introns,indicating the conservation of OsPIMT1 in the process of evolution and the importance of its function.2.The physiological and biochemical changes were investigated after the artificial aging of transgenic lines with OsPIMT1 and wild type Nipponbare seeds.The results showed that germination percentages of transgenic seeds overexpressing OsPIMT1 are higher than those of WT and RNAi lines after 13 days of aging treatment.3.OsPIMTl content and the isoAsp accumulation after artificial aging were determined.The results showed that the accumulation of isoAsp proteins in embryos isolated from overexpression line seeds was significantly lower than that in the WT seeds,whereas the RNAi lines tended to overaccumulate abnormal isoAsp in embryos during the whole treatment process,which indicated that the OsPIMT1-related longevity improvement is probably due to the repair of isoAsp-containing proteins that accumulate in embryos after artificial aging treatment.4.A total of 33 differential protein spots were identified by Two-dimensional gel electrophoresis.PIMT-based protein on-blot methylation analysis showed that there were a lot of isoAsp proteins with molecular weight of less than 55KD in embryos after artificial aging treatment.In our ongoing study,Two-dimensional gel electrophoresis and PIMT-based protein on-blot methylation analysis would be combined to identify the relation between isoaspartyl-containing proteins repaired by OsPIMT1 and differently expressed proteins related with seed aging,which would further elucidate the mechanism of OsPIMT1 in seed storability.