| The Loess Plateau region is one of the main apple production areas in China with abundant sunlight and preference temperature.However,less annual precipitation,uneven distribution of precipitation time and global warming climate caused water deficit,which significantly limits apple production in this area nowadays.Therefore,it’s of great significance to identify the key genes involved in drought resistance regulation from apple tree and uncover their resistance mechanism.The plasma membrane intrinsic aquaporin（PIP）is responsible for the transport of water,CO2 and other small molecule solutes across the cell membrane.This subject focused on the aquaporin gene MpPIP2;1 cloned from the drought-resistant Malus species Malus prunifolia.Transgenic apple seedling and Arabidopsis thaliana overexpressing MpPIP2;1 were obtained by genetic transformation,and subjected to drought and salt stress treatment to analyze the function of MpPIP2;1 in response to abiotic stresses.In addition,silicon was involved here,which is a beneficial element that alleviates plant drought,to analyze the role of apple PIP2;1 in silicon mediated drought stress alleviation.The main results obtained were as follows:1.The transgenic A.thaliana overexpressing MpPIP2;1 were obtained,which exhibited higher tolerances to drought and salt stresses compared to wild type.Under drought and salt stress conditions,the transgenic A.thaliana resulted in higher seed germination rate;longer primary root;higher survival rate with lower malondialdehyde content and relative conductivity,and higher antioxidant activity compared to wild type.This indicated that MpPIP2;1 gene could reduce the oxidative damage of A.thaliana seedlings and increase the activity of antioxidant enzymes to relieve stress and promote the growth of A.thaliana under drought and salt stress conditions.2.Overexpression of MpPIP2;1 in M.domestica seedlings‘GL3’was generated using agrobacterium-mediated transformation,and which was confirmed by molecular analysis at both DNA and RNA levels.3.Apple PIP2;1 gene might be involved in silicon mediated alleviation of drought stress in apple seedling.Under PEG induced drought stress in hydroponics or soil drought treatment,Malus hupehensis seedlings with exogenous silicon application,growing either in hydroponic or soil systems,had higher silicon content,improving photosynthesis with less oxidative damage and higher antioxidant activity compared to the control.Additionally,the level of apple PIP2;1 expression was upreguated by silicon application under drought stress.In summary,transgenic apple seedling and A.thaliana overexpressing MpPIP2;1 were obtained.Overexpression of MpPIP2;1 enhanced the drought and salt stress resistances in transgenic A.thaliana.In addition,apple PIP2;1 gene might participate in silicon mediated alleviation of drought stress in apple seedling.Silicon application could increase the silicon content in apple seedling,which exhibited better tolerance to drought stress.This course followed with higher level of apple PIP2;1 expression. |
