Proteomic analysis of the maize rachis: Potential roles of constitutive and induced proteins in resistance to Aspergillus flavus infection and aflatoxin accumulation

Abstract

Infection of the maize (Zea mays L.) with aflatoxigenic fungus Aspergillus flavus and consequent contamination with carcinogenic aflatoxin is a persistent and serious agricultural problem causing disease and significant crop losses worldwide. The rachis (cob) is an important structure of maize ear that delivers essential nutrients to the developing kernels and A. flavus spreads through the rachis to infect kernels within the ear. Therefore, rachis plays an important role in fungal proliferation and subsequent kernel contamination. We used proteomic approaches and investigated the rachis tissue from aflatoxin accumulation resistant (Mp313E and Mp420) and susceptible (B73 and SC212m) maize inbred lines. First, we compared rachis proteins from resistant and susceptible inbred lines, which revealed that the young resistant rachis contains higher levels of abiotic stress-related proteins and proteins from phenylpropanoid metabolism, whereas susceptible young rachis contains pathogenesis-related proteins, which are generally inducible upon biotic stress. Second, we identified A. flavus-responsive proteins in rachis of both resistant and susceptible genotypes after 10- and 35-day infection. Differential expression of many stress/defense proteins during rachis juvenility, maturation and after A. flavus challenge demonstrates that resistant rachis relies on constitutive defenses, while susceptible rachis is more dependent on inducible defenses.

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.…”

Development of Maize Host Resistance to Aflatoxigenic Fungi

“…A study was conducted to investigate the proteome of rachis tissue, maternal tissue that supplies nutrients to the kernels [75]. An interesting finding in this study is that after infection by A. flavus, rachis tissue of aflatoxin-resistant genotypes did not up-regulate PR proteins as these were already high in controls where they had strongly and constitutively accumulated during maturation.…”

“Omics” of Maize Stress Response for Sustainable Food Production: Opportunities and Challenges

“…A comparative proteomic analysis of rachises from a resistant and a susceptible maize genotype has been performed (Pechanova et al, 2011). The resistant line was found to primarily contain higher levels of abiotic stress-related proteins and phenylpropanoid metabolism related-proteins, whereas the susceptible line contained pathogenesis-related proteins.…”