The Mechanism Of Arabidopsis Cytoplasmic Invertase Relyingon Glucose Signal Pathway To Regulate Root Growth

Plants grow root,stem and leaf organs,supply nutrients mainly comes from two aspects of plant growth,on the one hand,from the roots of the plants,the root is a plant to adapt to the conditions of land for a long time after the formation of the plays an important role in the organs,in the process of plant growth and development have fixed plant,absorb water,synthesis and transport of nutrients needed for itself,and other functions.The roots of plants indirectly regulate the growth of the aboveground organs.Therefore,it is of great significance to study the regulation mechanism of plant root growth and development for people to deeply understand the whole development process of plants.There are many factors that affect root growth,among which sugar and hormone play important roles.Plant in the process of growth,on the other hand,the required nutrients also depends on the photosynthesis,from its own photosynthesis is one of the main nutrients of cane sugar,sucrose via phloem transport unloaded to the "library" organs,such as flower,fruit,seeds and root organs,such as library to meet these than photosynthesis organs demand for nutrients.However,sucrose cannot be directly used by plants.Instead,it is broken down into glucose and fructose under the action of enzymes,which can be used by plants as a carbon source and energy source.Therefore,it is of great significance to study the regulatory mechanism of sucrose utilization in the reservoir organs for people to understand the distribution and coordination of nutrients in plants and the process of growth and development.Cytosolic Invertase(CINV)is recognized as the most important enzyme for the decomposition of sucrose.This enzyme family is encoded by nine genes,among which CINV1 and CINV2 are the two most important enzymes.These two enzymes regulate the metabolism of sucrose in plants and control the entry of sucrose into cells.It plays an important role in plant growth,especially in root growth.However,the molecular mechanism of precise regulation of CINV1/2 enzyme activity remains unclear.In this study,Arabidopsis thaliana was used as the experimental material to study the mechanism of how roots use CINV to coordinate the nutrient sucrose from photosynthesis to better adapt to the environment at the early growth stage.The main research results are as follows:(1)the internal and external source the increase of sucrose content,can promote the growth of Arabidopsis thaliana root,at the same time CINV1 within the plant root activity and the content of glucose also will increase,and the added exogenous glucose can also promote the growth of Arabidopsis thaliana root,and the phenomenon of exogenous added sucrose showed consistent,at this time within the plant root CINV1 activity also show the enhancement,It is speculated that the ultimate factor of sucrose promoting root elongation is the promotion of root growth by increasing endogenous glucose level,and this process is caused by enhanced CINV1 activity.These results indicated that both exogenous sucrose addition and enhanced photosynthesis promoted root growth by activating CINV1 activity and then increasing endogenous glucose content.(2)Sucrose,the photosynthetic product of plants,is decomposed into glucose by CINV1,and glucose is sensed by its receptor HXK1.HXK1 has both signaling and metabolic functions,and it transmits glucose signals by signal function.These glucose signals in turn promote the degradation of glucose signal component EIN3.The hormonal effects of glucose on plant growth and development reflect the outputs of a complex signaling network controlled by nutrient,hormonal,and environmental inputs,which is partially regulated by the glucose receptor HXK1 for functional integration.In this study,it was found that EIN3 acted on the upstream of CINV1 in the process of root growth mediated by glucose signals,but was not directly bound to the initiation region of CINV1.Therefore,other signal elements between EIN3 and CINV1 were explored in this study.It was found that EIN3 directly binding to the promoter of PAP1 had a negative regulation effect on PAP1 expression,while PAP1 directly binding to the promoter of CINV1 and activating CINV1 expression had a positive regulation effect.It has been proved by relevant studies that PIP5K9 is upstream of CINV1 and negatively regulates the growth of Arabidopsis roots.Therefore,this study further explores whether there is a regulatory relationship between EIN3 and PIP5K9 in the regulation of Arabidopsis root growth.It was found that EIN3 directly binds to the PIP5K9 promoter region to activate the expression of PIP5K9 and negatively regulate the growth of Arabidopsis roots.Based on the above studies,the existence of GLC-HXK1-EIN3-PAP1/PIP5K9-CINV1-GLC signal regulation loop was found.Since HXKI has both signaling and enzymatic functions,this study demonstrated the signaling function of HXK1 in this regulatory loop through experiments,and also confirmed that the GLC-HXK1-EIN3-PAP1/PIP5K9-CINV1-GLC signal regulatory loop is in dynamic regulation in response to changes in the external environment.