Molecular Mechanism Of 35S: AtDREB1A Chrysanthemum Improving Tolerance To Heat Stress

Groundcover Chrysanthemum are cultivated in gardens and greenbelts worldwide with better ornamental and tolerance to extensive management. But,with the development of global warming, the sensitivity of this cultivar to heat stress has been the key factors limiting its cultivation in southern china. This study provide theoretic basis for DREB1A and its down stream network regulation mechanism, and actual basis for engineering breeding of groundcover Chrysanthemum.Over-expression of AtDREB1A in chrysanthemum transgenic plants conferred strong tolerance to heat stress. Transgenic plants with 35S:AtDREB1A construct and wild type plants were exposed to 45℃as heat stress treatment, When heat-treated for 36 h and followed by a 3-week recovery, the 35S plants have higher survival rate than the WT plants. The experiment of Paraffin section observation about the bud differentiation process indicates that both strains bud differentiation is restrained in 45℃high temperature conditions compared with the wild type, the restrained degree of transgenic plants is weaken. There is a relationship between cellmembrane injury rate, malondialdehyde content, soluble protein content and the expression of integrated exogenous gene. We speculate that the introduction of exogenous gene DREBIA can affect the various metabolie regulations in high temperature conditions, thereby strengthen the capacity of cellmembrane self-protection and embrane lipid peroxidation.Here, we isolated 74 genes up-regulated by AtDREB1A using suppression subtractive hybridization, and analyzed enhancement patterns of AtDREBIA regulon expression in 35S plants relative to wild type (WT) plants under the stress conditions through cDNA macroarray. We also found that the 35S plants maintained significantly higher photosynthetic capacity,and elevated activity of Rubisco and sucrose-phosphate synthase under heat stress. These results suggest that improvement of heat stress tolerance in transgenic chrysanthemum may be associated with enhanced capacity of photosynthesis.