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Poster: Biology & Disease Mgmt: Genetics of Resistance


Two SREBP Transcription Factors are Required for Ergosterol Biosynthesis and DMI Resistance in Penicillium digitatum
R. RUAN (1) (1) Institute of Biotechnology, Zhejiang University, China

Application of imazalil is a common method for control of citrus green mold caused by Penicillium digitatum. As a consequence of continuous use, imazalil-resistant P. digitatum strains have emerged worldwide. Our previous study showed that overexpression of imazalil target genes CYP51A and CYP51B, induced by the insertion mutations in their promoter regions, is responsible for the resistance. However, the regulators inducing overexpression of CYP51s are unclear. In this study, we demonstrated two SREBP homologs, designated as PdSrbA and PdSrbB. Both ?PdsrbA and ?PdsrbB showed markedly reduced ergosterol contents and increased sensitivities to imazalil and other DMIs, while double deletion led to hypersensitive to DMIs. ?PdsrbA but not ?PdsrbB is hypersensitive to terbina?ne and tridemorph, two SBIs targeting to ERG1 and ERG24, respectively. In addition, PdsrbA also mediated responses to iron-depletion and hypoxia. However, no change was observed in growth rate or virulence for those mutants. Expression of CYP51s and other genes involved in ergosterol biosynthesis was significantly down-regulated in ?PdsrbA and ?PdsrbB. These results suggested that these two SREBP homologs co-regulate ergosterol biosynthesis as well as DMIs resistance in P. digitatum, and PdsrbA may be with wider functions.