The PHD Transcription Factor Cti6 is Involved in the Fungal Colonization and Aflatioxin B1 Biological Synthesis of Aspergillus Flavus

Abstract

Aspergillus flavus and its main secondary metabolite AFB1 pose a serious threat to several important crops worldwide. Recently, it has been reported that some PHD family transcription factors are involved in the morphogenesis and AFB1 biological synthesis in A. flavus, but the role of Cti6, a PHD domain containing protein in A. flavus, is totally unknown. The study was designed to reveal the biological function of Cti6 in the fungus by deletion of cti6, and its two domains (PHD and Atrophin-1) through homologous recombination, respectively. The results showed that Cti6 might up-regulate the mycelium growth, conidiation, sclerotia formation and AFB1 biological synthesis of A. flavus by its PHD domain, while Atrophin-1 also improved the conidiation of the fungus. The qRT-PCR analysis showed that Cti6 increased the conidiation of the fungus through AbaA and BrlA mediated conidiation pathway, triggered the formation of sclerotia by orthodox sclerotia formation pathway, and improved the production of AFB1 by orthodox AFB1 synthesis pathway. Crops models analysis showed that A. flavus Cti6 plays vital role in colonization and the production of AFB1 on the host grains mainly via PHD domain. Bioinformatics analysis showed Cti6 is conservative in Aspergillus spp., and mCherry mediated subcellular localization showed that most Cti6 accumulated in the nuclei, which reflected that Cti6 performed its important biological function in the nuclei in Aspergillus spp.. The results of the current study elucidate the roles of PHD domain containing proteins in the mechanism of the infection of crops by A. flavus, and provided a novel target for effectively controlling the contamination of Aspergillus spp. to crops.

The Plant Homeodomain Protein Clp1 Regulates Fungal Development, Virulence, and Autophagy Homeostasis in Magnaporthe oryzae

“…For example, the nuclear protein ING2, which contains a PHD, interacts with PtdIns(5)P in vivo to regulate the ability of ING2 to activate p53 and p53-dependent apoptotic pathways ( 65 ). In M. oryzae , the PHD was indispensable for the function of Clp1, which is consistent with previous reports in other filamentous fungi ( 31 , 34 , 35 ). The clp1 Δ PHD strain, in which the PHD of Clp1 was deleted, had phenotypes similar to those of the Δ clp1 mutant.…”

“…In T. reesei , the growth of Δ clp1 is comparable to that of the wild type, but Δ clp1 has a severe defect in conidiation ( 34 ). In A. flavus , deletion of CTI6 results in attenuated growth and reduced conidiation ( 35 ). In M. oryzae , the Δ clp1 mutant also displayed decreased growth but increased conidiation.…”

“…In the filamentous fungus Trichoderma reesei , Clp1, a Cti6-like protein, is involved in the regulation of cellulase gene expression and sporulation ( 34 ). In another filamentous fungus, Aspergillus flavus , deletion of the CTI6 or PHD of CTI6 resulted in alterations in mycelial morphology, slowed growth, and reduced sporulation and decreased the biosynthesis of aflatoxin B1 (AFB1) ( 35 ).…”