HXK1 regulates carbon catabolism, sporulation, fumonisin B1 production and pathogenesis in Fusarium verticillioides

Abstract

In Fusarium verticillioides, a ubiquitous pathogen of maize, virulence and mycotoxigenesis are regulated in response to the types and amounts of carbohydrates present in maize kernels. In this study, we investigated the role of a putative hexokinase-encoding gene (HXK1) in growth, development and pathogenesis. A deletion mutant (Dhxk1) of HXK1 was not able to grow when supplied with fructose as the sole carbon source, and growth was impaired when glucose, sucrose or maltotriose was provided. Additionally, the Dhxk1 mutant produced unusual swollen hyphae when provided with fructose, but not glucose, as the sole carbon source. Moreover, the Dhxk1 mutant was impaired in fructose uptake, although glucose uptake was unaffected. On maize kernels, the Dhxk1 mutant was substantially less virulent than the wild-type, but virulence on maize stalks was not impaired, possibly indicating a metabolic response to tissue-specific differences in plant carbohydrate content. Finally, disruption of HXK1 had a pronounced effect on fungal metabolites produced during colonization of maize kernels; the Dhxk1 mutant produced approximately 50 % less trehalose and 80 % less fumonisin B 1 (FB 1 ) than the wild-type. The reduction in trehalose biosynthesis likely explains observations of increased sensitivity to osmotic stress in the Dhxk1 mutant. In summary, this study links early events in carbohydrate sensing and glycolysis to virulence and secondary metabolism in F. verticillioides, and thus provides a new foothold from which the genetic regulatory networks that underlie pathogenesis and mycotoxigenesis can be unravelled and defined.

Comparative analysis of phylogenetic relationships, morphologies, and pathogenicities among Curvularia lunata isolates from maize in China

“…Conidiation-related genes may therefore be linked to some extent with pathogenicity-related genes. This hypothesis is further supported by the results of various other studies on plant fungi (Yi et al, 2008;Kim et al, 2011). In the present study, no relationship was observed between the colony color and the pathogenicity of the isolates.…”

The role of MADS-box transcription factors in secondary metabolism and sexual development in the maize pathogen Fusarium verticillioides

“…For purification, FB1 crude extracts were passed through equilibrated HyperSep C18 SPE columns (Thermo Fisher Scientific) and ergosterol crude extracts were passed over Acrodisc 13 mm nylon 0.45 mm filters (Pall Life Sciences). HPLC analyses of FB1 and ergosterol were performed as described elsewhere (Shim & Woloshuk, 1999;Kim et al, 2011). FB1 levels were then normalized to ergosterol contents.…”

Identification of Novel Knockout Targets for Improving Terpenoids Biosynthesis in Saccharomyces cerevisiae

“…In addition, the genes encoding hexokinase (HXK1 and −2), aminotransferase (ALT2 and SER1) and the citrate transporter (CTP1) are positive knockouts for improving isoprenoid fluxes. HXK1 and −2 are isoenzymes acting on glucose metabolism in the upper glycolytic pathway [36], [37]. It was reported that deletion of HXK2 led to a 10-fold increase of HXK1 expression in S. cerevisiae strains [38].…”