Functional Analysis Of Salicylic Acid And Its Regulation-related Genes(SABP2?SAMT)in Plant Stress Tolerance

Abiotic stresses such as drought are the major environmental factors that severely limit the normal development of plants and the productivity of global crops.Salicylic acid(SA)is a plant hormone that plays an important role in the growth and development of plants and their response to abiotic stresses.In order to further study the function of endogenous SA in plant stress tolerance,the SA binding protein 2(SABP2)-like gene LcSABP and SA carboxyl methyltransferase(SAMT)-like gene LcSAMT which were related to SA metabolic regulation from Lycium chinense were isolated in our study.Then,transgenic tobacco plants with strong expression of LcSABP or LcSAMT were obtained via Agrobacterium-mediated genetic transformation method,respectively.The physiological and biochemical indexes of LcSABP overexpressing tobacco plants were tested.The results showed that the SA content,chlorophyll content,photosynthetic capacity,antioxidant enzyme activities and expression levels of stress-related genes in transgenic plants were significantly higher than those in wild-type(WT)plants after drought stress treatment.This suggested that LcSABP-mediated elevation of endogenous SA levels played positive regulatory role in plant responses to drought stress.In addition,under drought stress conditions,compared with the control group,overexpression of Lc SAMT in tobaccos down-regulated the endogenous SA levels,which further reduced plant tolerance to drought stress.And the LcSAMT transgenic plants showed the increased accumulation of ROS and MDA,decreased proline content and antioxidant enzyme activities.At the same time,the transgenic plants exhibited the increased sensitivity to drought stress which accompanied by a decrease both in the content of ABA and the transcription levels of genes involved in stress response.The above results demonstrated that LcSABP and LcSAMT-mediated changes in plant endogenous SA levels played an important regulatory role in plant responses to drought stress.In order to further explore the role of SA and its regulation-related genes(SABP2 and SAMT)in agricultural crops resistance to abiotic stresses,the potato plants were selected as the target plants to analyze the effects of SA and its metabolic regulation-related genes(SABP2 and SAMT)on plant response to heavy metal Cd stress through exogenous SA spraying.The results demonstrated that the contents of endogenous SA,chlorophyll,proline and antioxidant enzymes activity increased,and the contents of MDA,H₂O₂ and O₂^-decreased in potato plants with exogenous SA treatment under Cd stress.Additionally,the expression levels of stress-related genes and SA metabolism-related genes(StSABP2 and StSAMT)in potato plants were significantly increased after exogenous application of SA under Cd stress.This revealed that SA treatment enhanced the tolerance of potato to Cd stress,and StSABP2 and StSAMT genes involved in the process of plants response to Cd stress.