AUTHOR=Wang Liuqing , Wang Meng , Jiao Jian , Liu Hongmei 

TITLE=Roles of AaVeA on Mycotoxin Production via Light in Alternaria alternata

JOURNAL=Frontiers in Microbiology

VOLUME=13

YEAR=2022

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2022.842268

DOI=10.3389/fmicb.2022.842268

ISSN=1664-302X

ABSTRACT=<p><italic>Alternaria alternata</italic> is a principal plant pathogen responsible for the biosynthesis of mycotoxins, including tenuazonic acid (TeA), alternariol (AOH), and alternariol monomethyl ether (AME). The velvet gene <italic>VeA</italic> is involved in fungal growth, development, and secondary metabolism, including mycotoxin biosynthesis <italic>via</italic> light regulation. In this study, the detailed regulatory roles of Aa<italic>VeA</italic> in <italic>A. alternata</italic> with various light sources were investigated from the comparative analyses between the wild type and the gene knockout strains. In fungal growth and conidiation, mycelial extension was independent of light regulation in <italic>A. alternata</italic>. Red light favored conidiation, but blue light repressed it. The absence of Aa<italic>VeA</italic> caused the marked reduction of hyphae extension and conidiophore formation even though red light could not induce more spores in ΔAa<italic>VeA</italic> mutant. The differentially expressed genes (DEGs) enriched in hyphal growth and conidiation were drastically transcribed from the comparatively transcriptomic profile between the wild type and ΔAa<italic>VeA</italic> mutant strains with or without light. In mycotoxin production, TeA biosynthesis seems no obvious effect by light regulation, but AOH and AME formation was significantly stimulated by blue light. Nevertheless, the disruption of Aa<italic>VeA</italic> resulted in a marked decrease in mycotoxin production and the action of the stimulation was lost <italic>via</italic> blue light for the abundant accumulation of AOH and AME in the ΔAa<italic>VeA</italic> strain. From DEG expression and further verification by RT-qPCR, the loss of Aa<italic>VeA</italic> caused the discontinuous supply of the substrates for mycotoxin biosynthesis and the drastic decline of biosynthetic gene expression. In addition, pathogenicity depends on Aa<italic>VeA</italic> regulation in tomato infected by <italic>A. alternata in vivo</italic>. These findings provide a distinct understanding of the roles of Aa<italic>VeA</italic> in fungal growth, development, mycotoxin biosynthesis, and pathogenicity in response to various light sources.</p>