Map-based Cloning And Function Analysis Of The Premature Leaf Senescence Gene OsPLS3 In Rice

Early senescence of functional leaves,which are responsible for photosynthesis,significantly determines rice yield and grain quality.Therefore,studying the mechanisms of molecular and physiology of precocious leaf senescence is quite critical to rice resistance to premature aging.In this study,ospls3(Oryza sativa precocious leaf senescence 3)was obtained from a rice indica restore line N142 irradiated by 60Co.Then physiological,cytological and molecular methods were conducted to study ospls3 to detect its mechanisms of precocious senescence.The main results are shown as following:1.Compared with its wild type,ospls3 did not show any phenotypic differences before the four or five-leaf stage of development.When the plant progressed to the tilling stage,leaves except heart leaf exhibited early senescence.At late booting stage,all leaves were senescent.As a result,the main agronomic traits of ospls3 were significantly lower than its wild type.2.Genetic analysis and gene mapping verified that the ospls3 was a recessive nuclear mutant and OsPLS3 was located between RM28723 and RM28753 on chromosome 12 limited to a 294 kb region.Then,the sequencing results showed that LOC_Os12g42420 encoding a putative DNA binding protein lost 22 nucleotides from its exon,which led to frame-shifting mutation.Last,this gene was confirmed by functional complementation.3.The ROS measurement and histochemical staining indicated that large ROS was accumulated in ospls3 at booting stage,which caused membrane lipid peroxidation with increase of MDA and ion leakage rate.Compared with its wild type,both the detached leaves and the seedlings of ospls3 were sensitive to the exogenous H2O2.All these results indicated that the ROS accumulation played a critical role in premature leaf senescence.4.High concentration of exogenous 6-BA promoted senescence of detached leaves of ospls3 and inhibited its seedlings root number and length.In molecular analysis,most ERFs genes expression homologous to CRFs was significantly elevated in ospls3.