Analysis Of Lignin And Related Synthetic Gene Expression In Leymus Racemosus

Leymus racemosus(Lam.)Tzvel is a perennial tetraploid species with intensive reproductive structure and strong asexual reproduction ability in the Triticeae(Poaceae).As an endangered precious wild plant resource and an excellent sand-fixing plant,many genes,involving resistance to drought,salt,alkali,diseases and insect pests etc,have been recived much attantion by scientists.There is a close relationship between stress resistance and lignin biosynthesis.However,little known about the effects of stress resistance and the genes of lignin biosynthesis pathway in L.racemosus.In this study,the genes of lignin biosynthesis pathway were obtained by molecular cloning,and were analyzed using gene expression and enzyme activity monitoring.We also analyzed the effected on between lignin accumulation and the five key genes in the lignin biosynthesis pathway of L.racemosus.The main results are as follows:1.Five gene sequences,including 4CL,C3 H,C4H,F5 H and PAL,were obtained by the method of homologous cloning.Complete c DNA sequences of PAL genes was obtained using RACE.The PAL gene ORF is 2121 bp in length,encoding 697 amino acids.The protein size is 75.9 k Da.The length of 5’ non-coding region(5’-UTR)is 142 bp.The length of 3’ non-coding region(3’-UTR)with a 16 bp 3’Poly A tail is 262 bp.2.Monitoring the relative expression and acid-insoluble lignin content of the five genes in the annual growth cycle showed that the relative expression of 4CL,C4 H,F5H and PAL genes increased firstly and then decreased during the annual growth cycle,and the change trend was the same as that of lignin accumulation,but not synchronous.These four genes are the key nodes controlling lignin synthesis,and the accumulation of lignin increases with the expression of genes.On contrary,the change of C3 H gene first decreased and then increased,which had feedback regulation on lignin accumulation.3.Through the monitoring of peroxidase during the annual growth cycle,it was found that the change trend of lignin content and peroxidase activity was the same and synchronous.This indicated that peroxidase is necessary for the polymerization of lignin monomers,and there is no branching pathway.