Study On Relationship Between ABA And Different Senescent Phenotypic Of Rice

Rice is an important grain crop and economic crop in China.It has a wide area for planting and is the staple food for most people in China.In recent years,with the increase of the population and people's pursuit of quality of life,the simultaneous realization of high quality and high yield of rice has become a new direction of rice breeding in the new situation.It is necessary to break the contradiction between the high quality and high yield of rice and solve the problem of high quality of low yield,and low quality of high yield.For a long time,the factors that plagued the high yield of high-quality rice varieties are not strong resistance,low photosynthetic energy efficiency,and premature aging.Therefore,studying the aging mechanism and photosynthetic energy efficiency of rice has become a new breakthrough in solving the next rice breeding problem.In this study,the relationship between the endogenous hormone ABA and different senescent phenotypes of rice was studied.The sterile lines HD9802s,Y58s,and restorer lines Jin 23B,R287 were used as research materials,the research was conducted in differences of chlorophyll content,photosynthetic efficiency,ABA content,and the expression of ABA and chlorophyll metabolism related genes.The results were as follows:1.The results of photosynthetic efficiency showed that the photosynthetic indexes of the premature cultivars Jin 23B and Y58s were superior to those of the green rice varieties 8287 and HD9802s at the heading stage and grain filling stage,but they decreased even more faster during the milk ripening stage and the wax ripening stage.In the wax ripening stage,the photosynthetic efficiency of the premature-fail rice varieties is worse than that of the green rice varieties.2.Established a method for rapid determination of chlorophyll content in rice leaves.The results of different solvent extractions showed that the best extraction solution for chlorophyll in rice leaves was acetone:ethanol(1:1).When leached for 22 hours under shading at room temperature,the chlorophyll content in the extract was up to Peak.At the heading and filling stages,there was no significant difference in chlorophyll content between the green-susceptible and premature-decaying varieties.During the wax ripening period,the green-susceptible rice varieties HD9802s and R287 had higher chlorophyll a and chlorophyll b contents in comparison with the pro-progressive rice varieties Y5 8s and Jin 23 B,respectively.3.The ABA content of the four rice varieties gradually increased with the development process.From the heading stage,the endogenous ABA content of the early-decaying cultivars was higher than that of the chlorogenic cultivars.The ABA content in the Jin 23B was 1.16 times that in the R287,and the ABA content in the Y58s was 1.05 times that of the HD9802s.During the grain filling stage,milk ripening stage and wax ripening stage,the difference was increasing.In the wax ripening stage,the ABA content in Jin 23B was 1.17 times that in R287,and the ABA content in Y58s was 1.13 times that of HD9802s.4.The study of rice seedlings showed that application of exogenous ABA could induce leaf yellowing in rice seedlings.The results of the expression analysis of chlorophyll-related gene indicated that the expression of chlorophyll degradation-related genes increased continuously while the rice seedlings were treated with exogenous ABA.and the expression of NCED1,a gene related to ABA synthesis,increased first,and then stabilized or even decreased.This indicates that ABA may participate in the regulation of rice green by affecting the expression of chlorophyll metabolism genes.5.The results of analysis on the expression of ABA and chlorophyll biosynthesis-related genes in rice leaves at different developmental stages showed that the differences in gene expression between the green-susceptible rice varieties and the premature-decay rice cultivars mainly occurred during the wax ripening period.The green rice cultivars HD9802s and R287 compared the corresponding progeria rice varieties Y58s and Jin 23B,respectively.The chlorophyll synthesis-related genes CHLH and CHLI expression levels were relatively higher at the wax ripening stage,CHLH was about 2.16-fold and 1.31-fold respectively,CHLI were about 1.42 times and 1.85 times.At the same time,the chlorophyll degradation-related genes NYC3 and SGR were 0.81 fold,0.75 fold,0.83 fold and 0.77 fold,respectively.The expression of ABA synthesis gene NCED1 and degradation-related gene ABA80X1 decreased by 0.73 fold,0.83 fold and 0.72 fold,0.87 fold,respectively.These differences maintained the endogenous AB A content of the green rice cultivars during the wax ripening period is at relatively low levels,and the chlorophyll content is at a relatively high levels.Based on the above findings,we believe that the occurrence of different senescent phenotypes in rice is mainly due to differences in the expression levels of endogenous ABA and aging-related genes in different rice varieties at the milk ripening stage and the wax ripening stage.The endogenous ABA content of green-susceptible rice cultivars was lower than that of the early-decay rice cultivars during the milk ripening stage and the wax ripening stage.At the same time,the chlorophyll synthesis-related gene expression levels of green-susceptible rice varieties were higher than that of the premature-fat rice,the expression levels of chlorophyll degradation-related genes,ABA synthesis and degradation-related gene were lower than those of the early-decayed varieties.These characteristics together ensure that the green rice can maintain relatively low levels of ABA and relatively high levels of chlorophyll content during milk ripening and wax ripening stage.The above experimental results will provide theoretical guidance and material basis for the further study of the molecular mechanisms involved in rice endogenous ABA and senescence phenotypes.