| Aging is an age-dependent process,and its initiation is strictly regulated by endogenous factors including plant hormones and metabolic state.It is known that nutrient and water deficiency and shading can accelerate leaf senescence,because nutrient deficiency can promote protein hydrolysis and recycling of plant resources.Due to premature senescence,tillering,leaf spreading and noon photosynthesis were inhibited by drought stress.The accumulation of osmotic substances and organic acids,the decrease of photosynthetic efficiency and the change of carbohydrate metabolism are typical physiological and biochemical drought tolerance responses of rice.In the process of plants adapting to the external biological environment,protein phosphatase regulates the reversible phosphorylation process of several protein kinases to make plants adapt to the external environment.Type 2C protein phosphatase(PP2C)is a kind of protein phosphatase widely existing in plants.It regulates the growth and development of cells and signal transmission through dephosphorylation,thus adjusting the changes of related genes in vivo to resist stress.In the previous research,the rice gene Os SAG113 encoded by PP2 C protein phosphatase was screened,and the corresponding overexpressed transgenic rice and the corresponding mutant were obtained.In this experiment,the function of 35S-Os SAG113 transgenic rice and mutant ossag113 rice was analyzed,and the response of 35S-Os SAG113 transgenic rice and mutant ossag113 rice to drought stress was studied.The effective tiller number of transgenic rice with rice senescence-related gene Os SAG113 increased,leaf area decreased,SPAD value of flag leaf relative chlorophyll content decreased,photosynthesis weakened,heading was advanced,and plant leaves yellowed in advance.The effect on the physiological characteristics of rice is that the SOD activity,POD activity,CAT activity and soluble sugar content of 35S-Os SAG113 transgenic rice show a significant downward trend.The expression levels of transcription factors NAP,NAPR1,NKCL and SAG12 in transgenic rice with 35S-Os SAG113 senescence marker gene are higher than those in control SN9816,and the expression levels are on the rise with the aging.The expression of chlorophyll degradation related gene PAO increased with the aging process,and the expression of chlorophyll synthesis related gene CAO increased at tillering stage and heading stage of 35S-Os SAG113 transgenic rice,but decreased at wax ripening stage.Os SAG113 gene plays a positive role in regulating rice drought stress. |
