The Fuctional Study Of Auxin Response Gene Mdgh3-2/12 In Apple In Response To Salt And Low Nitrogen Stress

Apple is one of the main fruit trees in the world.It is widely planted in temperate regions.China has a long history of apple cultivation.As the world’s largest apple consumption and planting base,China’s apple planting area and output account for more than 50%of the world’s output,ranking first in the world.As a major apple producing area in China,Northwest China has abundant sunshine and large temperature difference between day and night,but dry climate,low annual average precipitation,poor terrain conditions of some orchards and inadequate irrigation conditions,drought,salt stress and lack of nitrogen have become the important factors restricting the development of apple industry in this region.Previous studies have confirmed that some GH3 genes will participate in plant growth and development and play an important role in response to abiotic stress.However,there are few studies on GH3 genes in apples.It has been previously proved in our laboratory that RNA interference with MdGH3-2/12apple plants decreased tolerance to drought.In order to further expand GH3 family in apple art function research,this experiment as the wild type GL-3 and RNA interference MdGH3-2/12-3 apple plant materials,has carried on the 15d 120 Mm/L NaCl hydroponic treatment and for a period of 25d 0.03 mM/L hydroponic low nitrogen treatment,phenotype of apple plants under salt stress,growth,photosynthetic parameters,MDA content,ROS,stress the expression of related genes,and the change of the enzyme system was analyzed,and to determine the growth index,photosynthetic parameters and related enzyme activities of plants under low nitrogen conditions.In this study,the responses of apple plants to salt stress and low nitrogen after MdGH3-2 and Md GH3-12 gene interference were investigated,which provided a theoretical basis for improving apple salt tolerance.The main research results are as follows:1.Under salt stress,RNA interference MdGH3-2/12 apple plants showed more brown spots and necrosis on leaf surface than GL-3 plants,which affected plant growth and photosynthesis.Chlorophyll content decreased more,MDA content and REL increased more;the stomatal opening of leaves also decreased significantly under salt stress;Pro content in RNAi lines increased significantly,while Asp content decreased.The accumulation of ROS in leaves was more than that of GL-3,but the activity of antioxidant enzymes was less than that of GL-3.The Na~+/K~+ratio of plants was higher than that of GL-3,but the changes of related ion transporters were not as sensitive as that of GL-3,Na~+can not be excreted,and the plant is poisoned by sodium ions.The above results show that,after interference with MdGH3-2/12gene,the resistance of apple plants to salt stress decreased.The MdGH3-2/12 gene plays an important role in salt resistance in apple plants.2.Under low nitrogen stress,the growth and biomass accumulation of MdGH3-2/12 affected plants were adversely affected.The physiological indexes such as net photosynthetic rate and chlorophyll content decreased.The accumulation of N,P and K in the body also decreased significantly compared with GL-3;the activities of nitrogen assimilation and absorption related enzymes NR,NIR,GS and GOGAT were also decreased compared with GL-3.The expression of nitrogen assimilation and transport related genes AMTs and NRTs were significantly decreased compared with GL-3.The above results indicated that the tolerance of apple plants to low nitrogen decreased after the interference of MdGH3-2/12 gene,the MdGH3-2/12 gene may also play an important role in the resistance mechanism of plants to low nitrogen stress.