AUTHOR=Zhang Shuai , Zhu Panpan , Cao Boning , Ma Shuyu , Li Ruolan , Wang Xie , Zhao Aichun 

TITLE=An APSES Transcription Factor Xbp1 Is Required for Sclerotial Development, Appressoria Formation, and Pathogenicity in Ciboria shiraiana

JOURNAL=Frontiers in Microbiology

VOLUME=12

YEAR=2021

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2021.739686

DOI=10.3389/fmicb.2021.739686

ISSN=1664-302X

ABSTRACT=<p>Sclerotinia diseases are important plant fungal diseases that, causes huge economic worldwide losses every year. <italic>Ciboria shiraiana</italic> is the main pathogen that results in mulberry sclerotia diseases. Sclerotia and appressoria play important roles in long-term pathogen survival and in host infection during life and disease cycles. However, the molecular mechanisms of sclerotial development and appressoria formation in <italic>C. shiraiana</italic> have not been well studied. Here, an Asm1p, Phd1p, Sok2p, Efg1p and StuAp (APSES)-type transcription factor in <italic>C. shiraiana</italic>, <italic>CsXbp1</italic>, involved in sclerotial development and appressoria formation was functionally characterized. Bioinformatics analyses showed that CsXbp1 contained an APSES-type DNA binding domain. The expression levels of <italic>CsXbp1</italic> were higher in sclerotia and during later stages of infection. Compared with wild-type strains, hyphal growth was slower, the number and weight of sclerotia were reduced significantly, and appressoria formation was obviously delayed in <italic>CsXbp1</italic> RNA interference (RNAi) strains. Moreover, the <italic>CsXbp1</italic> RNAi strains showed weakened pathogenicity owing to compound appressoria defects. Tobacco rattle virus-mediated host-induced gene silencing enabled <italic>Nicotiana benthamiana</italic> to increase its resistance to <italic>C. shiraiana</italic> by reducing the <italic>CsXbp1</italic> transcripts level. Thus, <italic>CsXbp1</italic> plays vital roles in sclerotial formation, appressoria formation, and pathogenicity in <italic>C. shiraiana</italic>. This study provides new insights into the infection mechanisms of <italic>C. shiraiana</italic> and plant resistance breeding.</p>