Regulation Mechanism Of BR-Induced And AOX1a Resistance To Salinity Stress In Brassica Juncea

BR, as a new and efficient plant growth regulator, plays a very extremely role in improving plants resistance to various stresses. Our previous study showed that BR could significantly increase the transcript level of the AOX1 a gene, and the AOX had similar functions to BR in improving plants response to stresses. In order to explore the regulation mechanism of between BR and AOX in plants resistance to stresses, mustard germplasm No.9 was used to study the regulation mechanism of BR in salt tolerance. To study the regulation mechanism of AOX1 a in mustard salt resistance, SHAM and AA was used in order to chemically inhibit and induce the expression of the AOX1 a gene; to study the regulation mechanism of BR in mustard salt tolerance, BR and BR inhibitor was used; to investigate the regulation role of H2O2 in mustard salt resistance, H2O2 and H2O2 inhibitor was used. The objective of this paper was to clarify the possible regulation pathway mediated by the BR-induced AOX1 a gene based on the changes of the AOX1 a gene expression, the ROS levels and relative enzyme activities, etc., among the different treatments.The main research conclusions are as follows:1.The c DNA fragments of DET1、DET2、DWF1、DWF4 from leaf tissue of Brassica juncea were amplified using the primers designed on the basis of the conserved domain of DET1 、 DET2 、 DWF1 、 DWF4 in Brassica rapa, Brassica oleracea,arabidopsis thaliana and Brassica napus.2. The relative transcript levels of Mustard DET1, DET2, DWF1,DWF4 gene are not affected by the AOX1 a gene, suggesting that BR biosynthesis may not be affected by the AOX1 a gene expression in the mustard.3. Under salt stress, BR could improve salinity tolerance by inducing the gene expressions of both AOX1 a and relative protective enzyme, increasing the activities of the protective enzymes, and reducing the contents of intracellular reactive oxygen species and MDA.4. Under salt stress, the induction of the AOX1 a gene expression can increase the activities of antioxidant enzymes, reduce the content of the reactive oxygen species and MDA in the plant cell, and thus enhance the salt resistance of plants.5. Under salt stress, BR can promote the accumulation of intracellular H2O2 and the increase of H2O2 can induce the up-regulation of the AOX1 a gene.