The Effects Of Molecular Regulation Of Caffeic Acid 3-O-methyltransferase On Lignin Biosynthesis And Plant Growth And Development

This dissertation consists two major parts of works related to COMT gene from wheat One is the work of tobacco. The binary vector pATCOMT, which containing the COMT cDNA from wheat, was constructed and transformed into tobacco. We studied the effects of antisense COMT cDNA on lignin biosynthesis and plant growth and development. The other is the work of wheat. We transformed the sense and antisense COMT cDNA into two kinds of wheat mediated by pollen tube method in order to get the data about the effects of molecular regulation on plant growth and development.1. Effects of Antisense COMT cDNA on Lignin Biosynthesis and Plant Growth and DevelopmentAntisense caffeic acid 3-O-methytransferase (COMT) cDNA of wheat was transformed into tobacco W38 mediated by Agrobcterium tumefaciens. The results of PCR, PCR-Southern analysis indicated that the cDNA was integrated into the genome of the transgenic tobacco. As compared to wild type plants, the phenotypes of 2-month-old transgenic plants (in vegetative growth period) were similar to the controls. In the flowering period, compared to wild type plants, 4-month-old transformants were dramatically dwarf, their lignin content were slightly lower, the S/G ratio was reduced and some xylem vessels of transformants were collapsed and deformed. We also found that the photosynthesis rate and transpiration rate of 2-month-old the first generation progenys of transgenic line ATCOMT-R were higher than controls. Our results suggest that the suppression of endogenous COMT expression can affect the lignin biosynthesis. With the accumulated process of effects of downregulation of COMT on lignification of plant secondary wall, the transgenic plants can display the abnormal characters.2. To get transgenic wheat by pollen tube methodSense and antisense COMT cDNA from wheat were transformed into the wheat through pollen tube method. About 2000 wheat floweuwere conducted on the flower stage of wheat and we got 1117 seeds in the end. We planted the seeds that fall and got 321 seedlings then. The total rate of seedlings alive was 28.7%. We gained 5 transgenic lines of wheat after screening using 80ppm PPT and identification of PCR. There is one positive plant of H4564 conducted with antisense gene, 2 positive plants of C6001 conducted with sense gene and 2 positive plants of C6001 conducted with antisense gene. We also found heights of transgenic wheats were much lower than controls, their growth and development were affected. Further study should be done to know whether there is some relation between the molecular regulation of COMT and the plant physiological changes.