Involvement Of Aspartate Transaminase(GOT1)in Magnaporthe Oryzae Pathogenic Development

Rice blast is one of the main rice diseases caused by Magnaporthe oryzae,which causes huge economic losses to rice production every year.Magnaporthe oryzae is a semi-biotrophic pathogenic fungi.During the biotrophic phase,Magnaporthe oryzae not only face the defense response of the host,but also deal with the threat caused by nutritional deficiencies.Amino acids are important nitrogen sources,which can not only be used as materials for protein synthesis,but also be metabolized for other biological processes.Earlier studies in our laboratory found that the aspartate metabolic pathway may be involved in the pathogenic process of Magnaporthe oryzae.This research aims to address this scientific issue,in terms of amino acid utilization of Magnaporthe oryzae to investigate the role of key genes of the aspartate metabolic pathway in the growth,development and pathogenicity.It lays a theoretical foundation for analyzing the pathogenic mechanism of Magnaporthe oryzae.The aspartate metabolism pathway in the organism is involved in the biosynthesis of various amino acids,and plays an important role in plants and humans.Aspartate-?-semialdehyde dehydrogenase?ASD?is involved in the aspartate metabolic pathway.Previous laboratory research found that the absence of ASD affects the pathogenic of Magnaporthe oryzae.This result preliminarily illustrates the contribution of the aspartate metabolic pathway to the pathogenicity of Magnaporthe oryzae.Aspartate aminotransferase?GOT1?is at the beginning of the aspartate metabolic pathway.In order to further confirm the pathogenic role of the aspartate metabolic pathway,we selected GOT1 as the research object and got the following results:1.Compared with the wild type strain,the growth rate of knockout mutant?GOT1 was slowed,and the colony melanin became lighter.2.The spore production capacity of?GOT1 and appressorium formation rate were reduced.3.The pathogenicity of?GOT1 was also weakened and the invasive hyphae growth rate of?GOT1 in plant cells was slower.Gene expression analysis showed that the expression level of GOT1 gene was up-regulated within 72 hours after infection,further confirming the correlation between GOT1 expression and pathogenicity.4.When cultured in a medium containing H₂O₂,NaCl,Congo red,and SDS,it was found that H₂O₂ significantly inhibited the growth of?GOT,but NaCl,Congo red,and SDS had no significant effect on the growth of?GOT1.5.When aspartate or asparagine was used as the sole nitrogen source in the medium,wild type strain could grow normally but?GOT1 grew extremely slowly,there was no significant difference in growth rate between?GOT1 and wild type strain when using NH₄⁺,NO₃^-,glutamine and other amino acids as the only nitrogen source.The above results indicate that GOT1 is involved in the mycelial growth,melanin synthesis,the resistance to ROS,conidia and appressorium formation,pathogenicity and the utilization of aspartate and asparagine.Since GOT1 is at the beginning of the aspartate metabolic pathway,this study proves the aspartate metabolic pathway is involved in the pathogenic development of Magnaporthe oryzae.