Multi‐factor regulation of pectate lyase secretion by Colletotrichum gloeosporioides pathogenic on avocado fruits

Abstract

Tissue alkalinization during Colletotrichum gloeosporioides attack enhances the expression of PELB, which encodes pectate lyase (PL), and PL secretion, which is considered essential for full virulence. We studied the regulation of PL secretion by manipulation of C. gloeosporioides PELB. PELB was down-regulated by knocking out PAC1, which encodes the PacC transcription factor that regulates gene products with pH-sensitive activities. We functionally characterized a PACC gene homologue, PAC1, from C. gloeosporioides wild-type (WT) Cg-14 and two independent deletion strains, Deltapac1(372)and Deltapac1(761). Loss-of-function PAC1 mutants showed 85% reduction of PELB transcript expression, delayed PL secretion and dramatically reduced virulence, as detected in infection assays with avocado fruits. In contrast, PELB was up-regulated in the presence of carbon sources such as glucose. When glucose was used as a carbon source in the medium for the WT strain and the Deltapac1 mutant at pH 6.0, PELB transcript expression and PL secretion were activated. Other sugars, such as sucrose and fructose (but not galactose), also activated PELB expression. These results suggest that the pH-regulated response is only part of a multi-factor regulation of PELB, and that sugars are also needed to promote the transition from quiescent to active necrotrophic development by the pathogen.

Development of new tools for studying gene function in fungi based on the Gateway system

“…This differential gene expression obtained by the RNAi mutants allowed us to obtain a series of mutant showing decreasing growth at pH 8.0, decreased alkaline phosphatase activity and PL secretion as the level of expression of PAC1 decreased (Figs. 3C and 4, Table 3) and confirm our early finding that PL secretion is Pac1 dependent (Miyara et al, 2008).…”

Priority colonization of Cinnamomum camphora litter by endophytes affects decomposition rate, fungal community and microbial activities under field conditions

“…Also, some endophytes may cause diseases in their hosts. For example, Colletotrichum gloeosporioides has often been encountered as endophyte in many studies (Hata et al, 2002;Hata and Sone, 2008;Osono and Hirose, 2009;He et al, 2012), but it may also cause anthracnose, black canker and leaf spot in host plants under certain conditions (Spiers and Hopcroft, 2007;Miyara et al, 2008;Embaby et al, 2010).…”

pH controls both transcription and post-translational processing of the protease BcACP1 in the phytopathogenic fungus Botrytis cinerea

“…PacC is a transcriptional activator of alkaline-induced genes and a transcriptional repressor of acid-induced genes (Tilburn et al, 1995). PacC and its regulatory pathway are conserved in fungi, and it has been demonstrated that this regulator participates in the virulence of some pathogenic fungi (Rollins, 2003;Caracuel et al, 2003;You & Chung, 2007;Miyara et al, 2008).…”