Identification of Maize Genes Associated with Host Plant Resistance or Susceptibility to Aspergillus flavus Infection and Aflatoxin Accumulation

Abstract

Background Aspergillus flavus infection and aflatoxin contamination of maize pose negative impacts in agriculture and health. Commercial maize hybrids are generally susceptible to this fungus. Significant levels of host plant resistance have been observed in certain maize inbred lines. This study was conducted to identify maize genes associated with host plant resistance or susceptibility to A. flavus infection and aflatoxin accumulation.ResultsGenome wide gene expression levels with or without A. flavus inoculation were compared in two resistant maize inbred lines (Mp313E and Mp04∶86) in contrast to two susceptible maize inbred lines (Va35 and B73) by microarray analysis. Principal component analysis (PCA) was used to find genes contributing to the larger variances associated with the resistant or susceptible maize inbred lines. The significance levels of gene expression were determined by using SAS and LIMMA programs. Fifty candidate genes were selected and further investigated by quantitative RT-PCR (qRT-PCR) in a time-course study on Mp313E and Va35. Sixteen of the candidate genes were found to be highly expressed in Mp313E and fifteen in Va35. Out of the 31 highly expressed genes, eight were mapped to seven previously identified quantitative trait locus (QTL) regions. A gene encoding glycine-rich RNA binding protein 2 was found to be associated with the host hypersensitivity and susceptibility in Va35. A nuclear pore complex protein YUP85-like gene was found to be involved in the host resistance in Mp313E.ConclusionMaize genes associated with host plant resistance or susceptibility were identified by a combination of microarray analysis, qRT-PCR analysis, and QTL mapping methods. Our findings suggest that multiple mechanisms are involved in maize host plant defense systems in response to Aspergillus flavus infection and aflatoxin accumulation. These findings will be important in identification of DNA markers for breeding maize lines resistant to aflatoxin accumulation.

Aflatoxin Resistance in Maize: What Have We Learned Lately?

“…These studies identified differentially expressed proteins from resistant versus susceptible maize genotypes both with [45][46][47][48] and without [49,50] infection of A. flavus during the experiment. Genome-wide association studies (GWAS) have also been brought to bear on the aflatoxin problem in maize.…”

“…Transgenic or mutant lines overexpressing or silencing the gene of interest were used to study the trypsin inhibitor gene [56], the PR10 gene [57], and the genes encoding lipoxygenase ZmLox10 [58] and lipoxygenase ZmLox3 [59]. Quantitative PCR has confirmed the differential expression of genes and proteins, although their functions have not been characterized [47,60]. Finally, reduced levels of aflatoxin can be correlated with a specific enzyme activity or protein component from infected maize kernels, for example, an aldose reductase [49], pericarp wax components [61], and 1-a Cys peroxiredoxin (PER 1), confirmed to be more expressed in one resistant maize inbred line than a susceptible inbred by Chen et al [62] but not associated with aflatoxin resistance in an association mapping panel by Warburton et al [33].…”

Factors controlling mycotoxin contamination in maize and food in the Hebei province, China

“…Aspergillus and Fusarium species can invade maize at different production stages especially during pre-and post-harvest handling (Chulze 2010). In warm and humid conditions, maize ears are ideal parts for colonization and dominance of Aspergillus flavus and Aspergillus parasiticus (Kelley et al 2012), resulting in aflatoxin formation. Fusarium species also cause a variety of diseases in maize, including seedling disease, stalk rots, and ear rots (Ma et al 2013).…”

Aflatoxins: biosynthesis, prevention and eradication

“…Enhancement of maize resistance to A. flavus infection is a desirable feature to reduce AF contamination at the preharvest stage of maize production. The maize resistance to A. flavus is a quantitative trait involving co-expression of many genes (Kelley et al, 2012). Identification of controlling genes and the gene network interaction is essential to the development of DNA markers and the transfer of maize resistance into commercial maize lines (Asters et al, 2015).…”