Functional Nalysis Of FgILV5 Invoived In The Branched Chain Amino Acid Biosynthesis Pathway In Fusarium Graminearum

Wheat scab (Fusarium head blight, FHB) is an epidemic disease of wheat crops (rye, barley, barley, wheat, etc.), which had occurred on all the wheat growing areas of entire country, especiallyYangtze River area is the most main area. In recent years, wheat scab has trended to Huang-Huai wheat area owing to the impact of changes in farming practices and other climatic factors (such as straw and global warming). Wheat Scab not only caused huge economic losses, but also reduced the quality of grain susceptible. It not only endangers human and animal health, but also threatens enormously food security mainly due to a variety of mycotoxins in susceptible grains as deoxynivalenol (DON) and zearalenone (ZEN). Currently due to lack of anti-scab of wheat varieties, the primary method for management of FHB is through fungicide application,because it only relies on benzimidazoles (carbendazim) fungicide, carbendazim resistant isolates have been frequently detected, Therefore, the development of new fungicide play a vital role in continued prevention and control of FHB.From the security point of agricultural products, certain biosynthetic pathways which are only present in a variety of organisms from bacteria to eukaryotes and higher plants, but not in animals become a hospot for developing a new safety drug target. E.g., BCAAs biosynthetic pathway, the body can only obtain by exogenous food, BCAAs are a class of essential amino acids, BCAAs biosynthesis enzyme is absent in the body.Thereby BCAAs synthase are only present in a variety of organisms from bacteria to eukaryotes and higher plants, but not in animals, the fact that make enzymes involved in these amino acids biosynthesis desirable targets for new herbicide and antimicrobial agents discovery. BCAAs biosynthesis enzyme becom potential drug target for developing non-toxic or low toxicity to mammals.In this study we characterized Fgllv5, a homologue of the Saccharomyces cerevisiae keto-acid reductoisomerase (KARI) from the important wheat head scab fungus Fusarium graminearum. KARI is a key enzyme in the branched-chain amino acids (BCAAs, including leucine, isoleucine and valine) biosynthetic pathway which exists in a variety of organisms from bacteria to fungi and high plants, but not mammals. The FgILV5 deletion mutant ? FgIlv5-4 failed to grow when the culture medium was nutritionally limited for BCAAs.When grown on PDA plates, ?FgIlv5-4 exhibited a significant decrease in aerial hyphae formation and red pigmentation. Conidia formation was also blocked in ?FgIlv5-4. Exogenous addition of 1 mM isoleucine and valine could rescue the defects of mycelial growth and conidial morphogenesis. Cellular stress assays showed that ?FgIlv5-4 was more sensitive to osmotic and oxidative stresses. In addition, virulence of ?FgIlv5-4 was dramatically reduced on wheat heads, and a low level of deoxynivalenol (DON) production was detected in ?FgIlv5-4 in wheat kernels. The expression level of TRI4, TRI5 and TRI6 in the mutant ?FgIlv5-4 was decreased by 92%,68% and 62%, respectively, as compared to those in wild type strain and complementary strain. Taken together, results of this study indicate that FgILV5 is involved in valine and isoleucine biosynthesis and is required for full virulence in F.graminearum.