Researches On The Dwarf Mechanism And Stress Tolerance Of Transgenic Perennial Ryegrass With DREB1A And BADH-CMO Gene

Perennial Ryegrass(Lolium perenne L.) is a widely planted cool-season turfgrass for utility turf, home lawns, sport fields, and golf fairways. Based on the construction of high frequency regeneration system of Perennial Ryegrass, DREBIA and BADH-CMO gene were transformed into embryogenic calli via biolostic bombardment by Xue Li. The transcription factor dehydration-responsive element binding proteins (DREB1A)/C repeat (CRT) binding factors (CBF) play an important role in regulating gene expression and growth involved in drought and salt stress tolerance. Choline monooxygenase (CMO) and betaine aldehyde dehydrogenase (BADH) catalyze the first and second steps in the biosynthesis of glycine betaine in betaine-accumulating plants. Not only enhanced drought and salt stress tolerance but also significant dwarfism had been observed from DREBIA and BADH-CMO transgenic Lolium perenne plants. The dwarf phenotype, dwarf mechanism and stress tolerance of transgenic Perennial Ryegrass was dicussed in this paper. The future vision of turgrass breeding and safety evaluation was also discussed. Conclusions of this reseach showed as followings:1. Height of transgenic plants was decreased obviously compared with the control. Measurement of endogenous GA content demonstrated that both GA1 and GA4 decreased in BADH-CMO transgenic plants and decreased GA1 content was observed in DREB1A/CBF3 transgenic plants, respectively. Dwarf trait of transgenic plants can be recovered by application of exogenous GAs. The result of relative expression level of GA20ox indicates that, relative expression level of GA20ox was decreased in transgenic plants with DREBIA gene and increased in transgenic plants with BADH-CMO gene, compared to control. The further study about function of GA20ox in mechanism of dwarfism was wanted. These results demonstrated that the DREB1A/CBF3 gene and BADH-CMO gene enhanced drought and salt tolerance and induced dwarfism in transgenic Lolium perenne. Dwarfism induced by DREB1A/CBF3 and BADH-CMO was associated with synthesis of endogenous GAs and it could be recovered by application of exogenous GAs.2. Enhanced drought, salt and high temperature stress tolerance had been observed in transgenic plants.In order to further understand the influence of exogenous GA on drought tolerance of transgenic plants with DREB1A/CBF3 and BADH-CMO gene, the research is focused on the analysis of the physiological properties of transgenic plants after drought and restoration treatment. The result of chlorophyll content,relative conductivity,relative water content,water content and sugar content showed that, drought tolerance of all materials was decreased by exogenous GA and the difference between transgenic plants and non-transgenic ones was significant. It suggested that exogenous GA had significant influence on drought stress tolerance of transgenic plants. The further study regarding on the mechanism of this phenomenon is wanted.3. The salt tolerance of transgenic plant seedling with DREB1A gene under different NaCl treatments was identified by determining the physiological indices. The results showed that the seed relative germination potential,relative germination rate,seedling height,chlorophyll Content,Water Content and RWC decreased with NaCl concentration increasing, and the difference was significant between transgenic group and control group. The rule of root length was not obvious. The contents of relative conductivity increased with the increasing of salt concentration and the difference between transgenic plants and CK was significant. This suggested that transgenic group was salt-tolerant. In order to study the double stress tolerance of T1 generation of transgenic plants with DREB1A gene, the research is focused on the analysis of the physiological properties of transgenic plants after PEG,NaCl and PEG+ NaCl treatment at germination stage, with the control group of water treatment. The result of relative germination potential,relative germination rate,seedling height,relative conductivity,wilting degree and chlorophyll content showed that, all materials with DREB1A gene showed the highest tolerance under NaCl stress. The result of relative water content and survival range indicated that materials with DREB1A gene had the highest tolerance under PEG stress. All materials with DREB1A gene had significant tolerance under PEG+ NaCl stress and the difference between transgenic plants and CK was significant. This suggested that T1 generation of transgenic Perennial Ryegrass was stress-tolerant and could be extended in drought and salinity soil to improve drought and salinity land.4. As to safety evaluation, transgenic Perennial Ryegrass with DREB1A/CBF3 and BADH-CMO gene was safe to environment.