AUTHOR=Huang Pengyun , Cao Huijuan , Li Yan , Zhu Siyi , Wang Jing , Wang Qing , Liu Xiaohong , Lin Fu-Cheng , Lu Jianping 

TITLE=Melanin Promotes Spore Production in the Rice Blast Fungus Magnaporthe oryzae

JOURNAL=Frontiers in Microbiology

VOLUME=13

YEAR=2022

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2022.843838

DOI=10.3389/fmicb.2022.843838

ISSN=1664-302X

ABSTRACT=<p>The rice blast pathogen, <italic>Magnaporthe oryzae</italic>, spreads through spores and invades rice through appressoria. Melanin is necessary for an appressorium to penetrate plant cells, but there are many unknown aspects of its role in fungal conidiation. In this study, we confirmed that melanin promotes spore production in <italic>M. oryzae</italic>, and that this effect is related to the background melanin content of wild-type strains. In the wild-type 70-15 strain with low melanin content of aerial hyphae, increased melanin synthesis promoted sporulation. In contrast, increased melanin synthesis in the wild-type Guy11 strain, which has higher melanin content, did not promote sporulation. The transcription factor Cnf1 (conidial production negative regulatory factor 1), which negatively regulates melanin synthesis, has opposite effects in conidiophore differentiation of Guy11 and 70-15. Deletion of <italic>CNF1</italic> did not abolish the defects of Δ<italic>cos1</italic> and Δ<italic>hox2</italic> (where <italic>COS1</italic>/conidiophore stalk-less 1 or <italic>HOX2</italic>/homeodomain protein 2 was deleted) in conidiation, while increased the conidiation of Δ<italic>gcc1</italic> and Δ<italic>gcf3</italic> (where <italic>GCC1</italic>/growth, conidiation and cell wall regulatory factor 1, or <italic>GCF3</italic>/growth and conidiation regulatory factor 3 was deleted). Pig1 (pigment of <italic>Magnaporthe</italic> 1) regulates the melanin synthesis of hyphae but not of conidiophores, spores, or appressoria. Deletion of the same gene in different wild-type strains can lead to different phenotypes, partly because of differences in melanin content between fungal strains. Overall, this study reveals the functional diversity and complexity of melanin in different <italic>M. oryzae</italic> strains.</p>