Interaction Mechanism Between Rhizosphere Microbes And Rice Plants Mediated By OsCIPK2 Gene Specifically Expressed In Root

Nitrogen is one of the indispensable factors in rice growth and development.The nitrogen has been mostly overused for rice production in China,therefore the nitrogen use efficiency is fairly low.It is a tough question how to decrease application of nitrogen and rise its utilization efficency for rice production.Many studies have been done for exploring the molecular and physiological mechanism,as well as the cultivation measures,but the interaction between rhizosphere environment and rice is poorly understood.There is complex interaction of plant roots and rhizosphere microbial flora,which plays very important role in soil nutrient supply and plant growth and development.In this study,we used the root specific expression OsCIPK2 transgenic rice to investigate the mutual effect between plants and rhizophere microbial mediated by CIPK2.The main results are showed as follows.Firstly,four nitrogen application rates have been seted in field(0,5,10,15kg N/667m2),to reseach the influence on rice yield and nitrogen use efficiency of specific expression CIPK2 in rice root Variance analysis demonstrated that the interaction of factors between rice genotype and nitrogen treatments showed extremely significant effect on yield.As the results,when nitrogen application rate was 0 and 5kg N/667m2,the yield and nitrogen uptake of root specific exprssion CIPK2 transgenic rice were significantly increased,of which the yield was increased by 11.3%and 5.75%,and the nitrogen uptake was increased by 11.75%and 4.42%,The improvement of rice yield was most significant under 0 nitrogen treatment.Regression analysis showed that root specific expression CIPK2 transgenic rice can reduce nitrogen application rate by 10.45%without decreasing yield.Further the experiment was implemented in pots,high throughput sequencing technology of bacterial 16S rRNA gene was used to analysis the bacteria communities of rhizosphere,rhizoplane,endosphere of rice under no nitrogen and nomal nitrogen treatment.The result showed that CIPK2 specifically expressed in rice root can increase diversity of bacteria communities in rice rhizosphere and rhizoplane under no nitrogen treatment.The relative abundance of ammoxidation bacteria Nitrospira and associative azotobacteria Arthrobacter,Flavobacterium,Azospirillum,Pseudomnas were also increased,which can promote the circulation and transformation of nitrogen in rhizosphere soil.The iron fluxes at root apical were detected by Non-invasive Micro-test Technique,it was found that root specific expression CIPK2 transgenic rice can absorb more Ca2+ and NO3-under low nitrogen condition.Finally,through investigating the growth of rice,the result showed that the root specific expression CIPK2 transgenic rice has more flourishing roots,more actively growing shoot,and the yield and nitrogen uptake were significantly increased,while there was no significant difference under nomal nitrogen treatment.In conclusion,under the condition of low soil nitrogen content,CIPK2 specifically expressed in rice root can increase diversity of bactria communities in rice rhizophere and rhizoplane,and change the bacteria communities in rice endosphere.The relative abundance of ammoxidation bacteria and associative azotobacteria significantly increased,which can promote the cycle of soil nitrogen and nitrifiction.Meanwhile,the rice can assimilate more NO3-to promote the growth of root system.The flourish root can absorb more nutrients to facilitate the growth and yield of rice.This preliminary study reveals the interaction mechanism between rhizosphere bacterial community and rice plants mediated by CIPK2,and action mode of the nitrogen assimilation in rice.The result laid the foundation for further reseach of nitrogen absorption and utilization of rice from rhizophere soil,and provided theory gist for studies on high-yielding and high-efficiency of rice.