Effects Of Growth And Development On Transgenic Populus Overexpressing Of PtDET2

Populus,playing an extremely significant role in ecological defense,beautifyingenvironment and industrial application,is one of the most important wood species inartificial forest.Conventional cross breeding programmes contributed greatly topopulous breeding and obtained many achievements.Fortunately,the development ofmodern biotechnology opens up genetically engineer trees for tree improvement,bywhich foreign genes can be transferred into target plant genomes.Brassinosteroids play an important role in plant growth and development process.BRs,by regulating many plant physiological responses such as: promoting cell redifferentiation,promoting growth,delaying senescence,enhancing plant resistance to environment stress and so on,,are essential for plant growth and development.BRs,the new plant growth accelerants next to other plant hormones: auxins,gibberelins,cytokinins,abascisic acid and ethylene.The steroid 5 alpha-reductase encoded by DET2 is important in the biosynthesis of brassinosteroid which plays an important role in plant growth and development.This paper is concerned with the transformation of Pt DET2 cloned from populous.The function of Pt DET2 had been investigated in transgenic tobacco and populous.The main results are as follows: 1.Construction of plant expression vectors and acquisition of transgenic plantsWe constructed a vector on the basis of vector PSH737,which gus::npt? fusion gene acted as a selection marker gene and a reporter gene named p SH-35S-Pt DET2.We obtained 52 lines of transgene 35S::Pt DET2 tobacco by leaf discs after screening and identification.2.Analysis of drought resistant function in transgene Pt DET2 tobaccoThe 3 different T1 seeds TP10,TP12 and TP15 were used to analyze the seed germination and seedling drought tolerance at 0,150 and 300 mmol/L mannitol simulated drought conditions.Results showed that the seed germination rate of transgenic plants were over 40% higher than that of wild type under 300mmol/L mannitol treatment for 15 d.Physiological-biochemical indices analyses showed that transgenic lines had higher super-oxide dismutase(SOD)contents,peroxidase(POD)contents and catalase(CAT)contents but lesser malondialdehyde(MDA)accumulation than wild type under drought resistant.Preliminary identification of Pt DET2 gene expression improves the drought tolerance of tobacco plants.3.Analysis of salinity resistant function in transgene Pt DET2 tobaccoThe 3 different T1 seeds TP10,TP12 and TP15 were used to analyze the seed germination and seedling salinity tolerance at 0,100 and 200 mmol/L Na Cl simulated salt conditions.Results showed that the seed germination rate of transgenic plants were over 50% higher than that of wild type under 200mmol/L Na Cl treatment for 15 d.Physiological-biochemical indices analyses showed that transgenic lines had higher super-oxide dismutase(SOD)contents,peroxidase(POD)contents and catalase(CAT)contents but lesser malondialdehyde(MDA)accumulation than wild type under Na Cl resistant.Preliminary identification of Pt DET2 gene expression improves the Na Cl tolerance of tobacco plants.4.Effect of overexpression Pt DET2 on tobacco stem vascular bundles and pithThe study found that rephloem layer of transgene 35S::Pt DET2 were 2.28,2.83 and 2.89 fold than wild type.Studies have shown that the length of transgene tobacco was larger than wild type.5.Genetic transformation of populusThe target gene transformation was conducted via recombinant plasmid,and 3 plantlets were proved to be positive transgenic plants by GUS histochemical assy and PCR analysis.The results showed the transgenic line,compared with control,exhibits more numerous and longer xylem fibers,more branches.Overexpression of Pt DET2 promoted the initiation and growth of lateral roots,hypocotyl and adventitious roots.The relationship of BRs to various phytohormones was further investigated using transgenic tobaccos overexpression Pt DET2 background.IAA and BRs independently promote hypocotyl elongation,but counteract in promoting root growth,while IBA and BRs counteract in promoting hypocotyls elongation,but enhance root growth independently.KT and BRs act counteraction in promoting hypocotyls,but act independently on root growth.GAs and BRs act counteraction in promoting hypocotyls,but act independently on root growth.BRs exhibit relatively independently on the growth,and these tow hormones act counteraction on root growth.6.Effect of overexpression Pt DET2 on populus stem vascular bundles and pithCompared with WT control,transgenic populus has thicker xylem,more numerous ray cells and wooden fiber cells,larger cell volume and numbers.