Functional Studies Of Populus Euphratica BR Biosynthesis Enzyme Gene PeDWF4

Brassinosteroids(BRs), a new class of phytohormones, play an extremely important role in plant growth and development, including seed germination, cell elongation, differentiation of vascular bundles, photomorphogenesis, plant fertility,aging, etc. Furthermore, it also can enhance the plant’s ability adapting a variety of environment stress. Currently, investigations on regulation mechanisms of BR biosynthesis and roles in plant growth are mainly focused on annual herbs such as rice, peas and Arabidopsis, fewer in perennial woody plants. DWF4 is a crucial rate limiting enzyme gene in BR biosynthesis pathway. Woody plants are significantly different from herbs in morphology, physiology and other aspects, but it’s still unclear wether the function of DWF4 in woody plants is exactly the same as that in herbs and no one has done research yet. To investigate the function of DWF4 gene in perennial woody, we use the expression vector with DWF4(Pe DWF4), which is homologous to Arabidopsis DWF4(AtDWF4), to transform Arabidopsis dwf4 mutant through inflorescence dip method, and obtained several Atdwf4-PeDWF4 homozygous transgenic lines. Systematic comparison and analysis were producted in morphology,anatomy, genetics, physiology and molecular characterization. The main results are as follows.1. Total four Atdwf4-PeDWF4 homozygous transgenic lines, named C12-2, C14-1,C16-1 and C18-1, were obtained through PCR identification.2. Mophological analysis revealed that compared with Atdwf4 mutant, the number of rosette leaves, leaf area, ratio of leaf length to width, petiole length, cell length and width of rosette leaf, veins cell length and lobe numbers of the transgenic lines were obviously increased, while stomatal density exhibited a decrease. In comparision with WT, the number of rosette leaves, petiole length, seed length and width as well as grain weight were significantly increased, but the length and width of rosette leaf, leaf area, stem diameter, silique number, inflorescence size and budnumber were decreased. But the seed number of single pod, branch number of stem was basically the same as that of WT.3. Physiological study showed that under the light and dark, the elongation rates of hypocotyls and primary roots of transgenic lines was significantly increased compared with Atdwf4 mutant. Compared with WT, the elongation rate of their hypocotyls increased, while the elongation rates of primary roots decreased.4. RT-PCR analysis showed that the expression levels of PeDWF4 in the transgenic lines was C16-1<C12-2<C18-1<C14-1. The expression level was negatively correlated with the degree of recovery phenotype.These results suggest that the roles of PeDWF4 and AtDWF4 in the regulation of plant growth and development are similar but possibly not exactly the same. Specific reason is open to study.