Phenotype Identification And Genetic Mechanism Of A Lesion Mimic Mutant Lmm-t In Rice

The rice lesion mimic mutant can usually activate disease defense response and enhance the disease resistance.Therefore,people were enough to excavate rice lesion mimic mutants and clone the related genes that helping to enrich the mechanism of the lesion mimic and laying a theoretical foundation for further study of programmed cell death and its resistance mechanism in rice.In this research,we have identified a rice lesion mimic mutant and analyzed its genetic mechanism.The mutant derived from a gene Os06t0675300 overexpression transgenic rice was obtained from the Oryza sativa L.ssp.Japonic Nipponbare,temporary called Lmm-t.Under natural conditions,the red-brown spots appeared on the young panicle of mutant Lmm-t.Subsequently,the spots gradually spreaded from the leaf tip to sheath,and downwarded along both edges of the leaf blade,the lesion mimic phenotype has been the entire growth period.Under natural conditions,the red-brown spots appeared on the leaves at the heading stage of mutant Lmm-t.Subsequently,the spots gradually spreaded from the leaf tip to sheath,and downwarded along both edges of the leaf blade,the lesion mimic phenotype has been the entire growth period.The agronomic traits of the mutant Lmm-t compared with the wild type plants showing a significant difference,such as tiller number,plant height,flag leaf,pamicle length and seed setting rate.Compared with the wild type,the ROS accumulated excessively and the activity of its etabolic enzyme was enhanced in the mutant Lmm-t,then the leaf cells were necrotic.The results showed that the resistance of Lmm-t mutant to 10 Filipino physiological races was significantly enhanced through the resistance analysis of Xoo with both mutant Lmm-t and wild type plants.And the expression of some pathogenesis-related genes were up-regulation in mutant Lmm-t.Through the resistance screening of the hygromycin and the Southern hybridization analysis with the mutant Lmm-t and the separation plants,indicating that the phenotype of the mutant Lmm-t caused by T-DNA insertion as a single copy.The mutation phenotype are dominant in genetics.The T-DNA insertion site was found in mutant Lmm-t genome through TAIL-PCR and sequencing,then we used PCR amplification to verify the insertion site.On one hand,we analysed the three candidate genes near the upstream and downstream of the insertion site by Real-time PCR,the expression of one of the candidate gene 0s02g0131700 was up-regulation caused by the T-DNA insertion.Then we constructed the overexpression vector of this gene,and obtained the transgenic lines of Nipponbare,which set the stage for the phenotypic identification subsequently.On the other hand,overexpression of the gene Os06t0675300 may also cause the lesion mimic mutant Lmm-t producing lesion mimic phenotype.These results provided a solid foundation for the cloning and functional research of Lmm-t mutant genes subsequently.