Genetic Analysis And Fine Mapping Of Es-t Mutant In Rice (Oryza Sativa L.)

Rice is one of the most important grain crops in our country. Rice leaves senescence affect the photosynthetic efficiency of rice directly, and have great influence on rice yield. With the completion of sequencing its genome which published on the Internet and improvement of the basic study, rice is one of the most important model organisms. Therefore, developing the research of rice leaf senescence is most important for us to reveal the molecular mechanism of senescence, control and cultivate the anti-senescence variety. We identified a early-senescence rice mutant es-t from the mutant liabrary built, map-based cloning method was used to complete the gene mapping, and it will facilitate the positional cloning and shed light on the study on molecular mechanism of leaf early-senescence. The following are the results of our study:1. The leaf showed yellow since seeding stage, and the chlorophyll content was also decreased in es-t. The rusty spots were found with its growth, especially in leaf margin and tip. The plant showed a typical early-senescence in milky stage.2. The root growed slowly after germination in the mutant es-t, the length of main root was shorter in es-t than wild-type; the mutation of Es-t also affected yielding ability, which showed that its 1000-weigh, the number of the primary branches, number of grains per ear and number of tillers, were also fewer than wild-type. In addition, the spots and some break clever were found in the seeds of mutant when it is mature.3. The content of chlorophyll was lower in the mutant than wild-type, especially the content of chlorophyll a, but the ratio of the content of chlorophyll a from the content of chlorophyll b was not changed basically and fitted the normal ratio of 3:1.4. The mutant es-t showed smoother leaf surface than wild-type under scanning electron microscope, and it lacked siliceous protuberance around the stoma in leaf. Morever, the results of transmission electron microscope were that the chloroplasts with abnormal shape grow abnormally and filled with many large starch grains in es-t. Paraffin section analysis showed the development of prothenchyma and vascular bundles were also abnormal in the mutant.5. Genetic analysis indicated that the mutant es-t was a new early-senescence mutant and controlled by a recessive gene, and was different from the gene including dwl1, spl-7, spl-11 and spl-28, which have found already.6. Map-based cloning method was used to map the gene. The gene was finally fine delimited in a 42-kb interval on chromosome 5, with six open reading frames in this area.In this study, we illustrated the changes caused by the mutation of rice from morphology, physiology, tissue section and so on. All of these studies showed that, ES-t was the key gene in the normal growth and development of rice, the results of fine mapping was useful for the further gene mapping, illustration of the molecular mechanism of leaf senescence, and regulation of the leaf senescence procession, in order to serve to the agricultural production effectively and provide it with theoretic foundation.