Amylopectin Induces Fumonisin B₁ Production by Fusarium verticillioides During Colonization of Maize Kernels

Abstract

Fusarium verticillioides, a fungal pathogen of maize, produces fumonisin mycotoxins that adversely affect human and animal health. Basic questions remain unanswered regarding the interactions between the host plant and the fungus that lead to the accumulation of fumonisins in maize kernels. In this study, we evaluated the role of kernel endosperm composition in regulating fumonisin B1 (FB1) biosynthesis. We found that kernels lacking starch due to physiological immaturity did not accumulate FB1. Quantitative polymerase chain reaction analysis indicated that kernel development also affected the expression of fungal genes involved in FB1 biosynthesis, starch metabolism, and nitrogen regulation. A mutant strain of F. verticillioides with a disrupted a-amylase gene was impaired in its ability to produce FB1 on starchy kernels, and both the wild-type and mutant strains produced significantly less FB1 on a high-amylose kernel mutant of maize. When grown on a defined medium with amylose as the sole carbon source, the wild-type strain produced only trace amounts of FB1, but it produced large amounts of FB1 when grown on amylopectin or dextrin, a product of amylopectin hydrolysis. We conclude that amylopectin induces FB1 production in F. verticillioides. This study provides new insight regarding the interaction between the fungus and maize kernel during pathogenesis and highlights important areas that need further study.

MED18 interaction with distinct transcription factors regulates multiple plant functions

“…Statistically significant changes were determined by R-package V3.16.5 (Po0.05, t-test). Gene expression was determined by quantitative RT-PCR (qPCR) using the Arabidopsis Actin2 gene as a reference for normalization as described 51 .…”

HISTONE MONOUBIQUITINATION1 Interacts with a Subunit of the Mediator Complex and Regulates Defense against Necrotrophic Fungal Pathogens inArabidopsis

“…A. brassicicola growth was determined using qPCR amplification of the fungal Cutinase DNA (Ab CutA). The relative DNA levels were calculated by the comparative cycle threshold method (Applied Biosystems) with Arabidopsis Actin2 as the endogenous reference for normalization as described (Bluhm and Woloshuk, 2005). The statistical significance of the differences in the mean values was analyzed as described in the legend for Figure 1.…”

“…Three technical replicates of the qPCR assay were used for each sample, and there were at least two biological replicates. The DNA levels were calculated by the comparative cycle threshold method (Applied Biosystems) with Arabidopsis Actin2 as the endogenous reference for normalization as described (Bluhm and Woloshuk, 2005).…”

“…The PCR was performed for 28 cycles using 2.5 mL of cDNA as a template and specific primer pairs (948C for 30 s, 528C for 30 s, and 728C for 1 min). qPCR was performed essentially as described by Bluhm and Woloshuk (2005). Total RNA (1 mg) was reverse transcribed using oligo(dT) primers and superscript II reverse transcriptase (Invitrogen).…”

Low pH regulates the production of deoxynivalenol by Fusarium graminearum

“…For example, the production of fumonisin by Fusarium verticillioides during infection of maize ears is triggered by amylopectin, a component of starch (Bluhm & Woloshuk, 2005). In Aspergillus nidulans, endogenous and exogenous oxylipids differentially regulate sterigmatocystin and penicillin production (Tsitsigiannis & Keller, 2006).…”