Functional Analysis Of Chitinase Genes Of Larix Gmelinii

Chitinase is a pathogenesis-related protein that plays an important role in defense to fungi plants,the chitinase protein functions in reducing the freezing point,inhibiting the growth and recrystallization of ice crystals,and enhancing resistance to freezing injury.Therefore,the chitinase gene provides an important candidate gene for plant genetic engineering of disease resistance and cold tolerance.In this studay,transcriptome of Larix gmelinii was analyzed by RNA-Seq technology.,and chitinase gene family in the larch was investigated.On the other hand.the functions of the chitiase genes isolated from Larix gmelinii in our previous study were investigated by transforming Arabidopsis.The main result are as follows:1.The RNA-Seq analysis showed that 7 of chitinase genes were found in transcriptome of L.gmelinii,involved in chitin binding,chitinase activity,cellular metabolirc processes,chitin catabolism,and chitinase defense.The results laid a foundation for the systematic analysis of chitinase gene characterisstics,regulatory mechanisms and biologyical function of Larix gmelinii.2.For analyzing the function of Lgchi genes,transgenic Arabidopsis thaliana lines were obtained using Arabidopsis tumefaciens-mediated transformation.The experimental results of low temperature stress showed that the chitinase activity increased and then decreased with the increase of stress time.The chitinase activity of transgenic Arabidopsis plants was significantly higher than that of the wild type,and the chitinase activity of transgenic lines over-expressing Lgchia2 is greater than that of transgenic lines over-expressing Lgchia1,indicating that the chitinase.genes play a role in cold tolerance.3.Under the cold stress conditions,the antioxidant enzyme activities were significantly increased,and the antioxidant enzyme activities of transgenic plants were higher than those of wild-type plants,indicating that overexpression of Lgchia1 and Lgchia2 enhanced the cold resistance of the transgenic Arabidopsis.4.The experimental results of infection with Fusarium oxysporum showed that the chitinase activity of the infected plants was increased first and then and chitinase activity activities of transgenic plants overpressing Lgchi1 and Lgchi2 were higher than those of wild-type plants.In addition,The spread of lesions on leaves of transgenic plants is slower than that of wild-type plants,confirming that the overepression of Lgchi1 and Lgchi2 improved the disease-resistance of transgenic plants.The above results provide a basis for the further analysis of the function.These results laid a foundation for further analysis of the function and mechanisms of the chitinase genes in L.arix gmelinii defense against low temperature and disease,and provided valuable candidate for genetic engineering for improving cold-tolerance and disease-resistance of crops and forest trees.