Involvement of ZFR1 of Fusarium verticillioides in kernel colonization and the regulation of FST1, a putative sugar transporter gene required for fumonisin biosynthesis on maize kernels

Abstract

Fumonisins comprise a class of carcinogenic mycotoxins produced by Fusarium verticillioides during colonization of maize kernels. In previous work, we identified ZFR1, which is predicted to encode a Zn(II)2Cys6 zinc finger transcription factor required for fumonisin B(1) (FB(1)) production during growth on kernels. In this study, we characterized the role of ZFR1 in colonizing maize kernels and inducing FB(1) biosynthesis. The ZFR1 deletion strain (Deltazfr1) grew approximately 2.5-fold less than the wild-type on endosperm tissue and a variety of other carbon sources, including glucose and amylopectin. However, the Deltazfr1 strain displayed higher alpha-amylase activity and expression of genes involved in starch saccharification than the wild-type, thus indicating that the reduced growth of the Deltazfr1 strain was not due to inhibition of amylolytic enzymes. In the wild-type strain, expression of six genes encoding putative sugar transporters was significantly greater on endosperm tissue than on germ tissue, and expression of at least three of the six genes was negatively affected by disruption of ZFR1. Intriguingly, disruption of FST1 had no effect on growth, kernel colonization or kernel pH but decreased FB(1) production by approximately 82% on maize kernels. Based on these findings, we hypothesize that ZFR1 controls FB(1) biosynthesis by regulating genes involved in the perception or uptake of carbohydrates.

Lae1 regulates expression of multiple secondary metabolite gene clusters in Fusarium verticillioides

“…Furthermore, many environmental and nutritional factors affect gene expression via broad-domain transcription factors. In F. verticillioides, nitrogen regulatory elements, pH regulatory elements as well as sugar transporters affect FUM gene cluster expression (Bluhm and Woloshuk, 2006;Bluhm et al, 2008;Flaherty et al, 2003;Kim and Woloshuk, 2008). In Aspergillus, genes that regulate conidia and ascospore production also affect secondary metabolite pathways (Bayram and Braus, 2011 and references therein).…”

PHL1 of Cercospora zeae-maydis encodes a member of the photolyase/cryptochrome family involved in UV protection and fungal development

“…Strains Dphl1-1 and Dphl1-2 (disrupted in PHL1) were constructed as described below. Strains WT-GUS and phl1-GUS were constructed by transforming strains SCOH1-5 and strain Dphl1-2, respectively, with plasmid pDB23, a vector constructed by cloning a geneticin-resistance cassette from pKS-GEN (Bluhm et al, 2008), into the EcoRI site of vector pNOM102 (GenBank Accession No. Z32701).…”

Functional Characterization of fst1 in Fusarium verticillioides During Colonization of Maize Kernels

“…Acquisition of the starch-derived sugars by the fungus requires sugar transporters. The genome of F. verticillioides has at least 147 putative genes that encode proteins with significant similarity to sugar transporters, none of which has been biochemically characterized (Bluhm et al 2008). The F. verticillioides gene fst1 was identified by comparative microarray analysis of RNA isolated from colonized maize germ and endosperm.…”