Aspergillus flavus infection induces transcriptional and physical changes in developing maize kernels

Abstract

Maize kernels are susceptible to infection by the opportunistic pathogen Aspergillus flavus. Infection results in reduction of grain quality and contamination of kernels with the highly carcinogenic mycotoxin, aflatoxin. To understanding host response to infection by the fungus, transcription of approximately 9000 maize genes were monitored during the host-pathogen interaction with a custom designed Affymetrix GeneChip® DNA array. More than 4000 maize genes were found differentially expressed at a FDR of 0.05. This included the up regulation of defense related genes and signaling pathways. Transcriptional changes also were observed in primary metabolism genes. Starch biosynthetic genes were down regulated during infection, while genes encoding maize hydrolytic enzymes, presumably involved in the degradation of host reserves, were up regulated. These data indicate that infection of the maize kernel by A. flavus induced metabolic changes in the kernel, including the production of a defense response, as well as a disruption in kernel development.

Near Infrared Spectrometry for Rapid Non-Invasive Modelling of Aspergillus-Contaminated Maturing Kernels of Maize (Zea mays L.)

“…This may be due to an increase in the sugar content as the fungus increased amylase activity and catabolised complex carbohydrates [36]. Similarly, the minimal catabolism of the dough samples were close in features to the dent stage samples.…”

“…This demonstrated that the spectral pre-treatment corrected for the differences due to path length alone and highlighted the differences in chemical composition [44,47]. The accumulation of free amino acids are reported in the less mature kernels compared to the more mature kernels [36,48]. Also, there is increased starch accumulation as the kernels mature [49,50].…”

“…In gene expression profiles, Reese et al [35] identified that genes for amino acid transport, carbohydrate and protein metabolism were active during aflatoxin metabolism at different stages of grain maturity. Also, Dolezal et al [36] identified expression of genes associated with starch metabolism and hexose mobilization genes during aflatoxin metabolism at different stages of crop maturity. These studies demonstrate that aflatoxin contamination occurs at different stages of grain maturity.…”

Global health issues of aflatoxins in food and agriculture: challenges and opportunities

“…Host resistance is a very attractive area on aflatoxin research, and various aspects of A. flavus-plant host interaction were investigated with special focuses on mechanisms resistant to fungal growth and aflatoxin production (Dolezal et al, 2014;Fountain et al, 2014;Hruska et al, 2014;Scarpari et al, 2014;Shan and Williams, 2014). In the up-to-date review on environmental influences on aflatoxin production on maize, Fountain et al (2014) detailed the history of research on this complex interaction and pointed out future directions for elucidating host resistance and susceptibility to A. flavus colonization in relation to abiotic stress such as drought and heat stresses, and oxidative stress in which aflatoxin may function as an antioxidant to the producing fungus.…”

“…Their results highlighted the important role of maize oxylipins in driving secondary metabolism in A. flavus. In the microarray study to identify maize genes expressed during pathogen infection, Dolezal et al (2014) found that metabolic processes are linked to defense responses, which include physical changes within the kernel as well as a disruption in kernel development. Shan and Williams (2014) provided a concise but clear overview of current knowledge about quantitative trait loci of corn related to aflatoxin contamination and ongoing efforts in the development of resistant corn lines.…”