A Maize Lectin-Like Protein with Antifungal Activity against Aspergillus flavus

Abstract

The filamentous fungus Aspergillus flavus causes an ear rot on maize and produces a mycotoxin (aflatoxin) in colonized maize kernels. Aflatoxins are carcinogenic to humans and animals upon ingestion. Aflatoxin contamination results in a large loss of profits and marketable yields for farmers each year. Several research groups have worked to pinpoint sources of resistance to A. flavus and the resulting aflatoxin contamination in maize. Some maize genotypes exhibit greater resistance than others. A proteomics approach has recently been used to identify endogenous maize proteins that may be associated with resistance to the fungus. Research has been conducted on cloning, expression, and partial characterization of one such protein, which has a sequence similar to that of cold-regulated proteins. The expressed protein, ZmCORp, exhibited lectin-like hemagglutination activity against fungal conidia and sheep erythrocytes. Quantitative real-time PCR assays revealed that ZmCOR is expressed 50% more in maize kernels from the Mp420 line, a type of maize resistant to A. flavus, compared with the expression level of the gene in the susceptible B73 line. ZmCORp exhibited fungistatic activity when conidia from A. flavus were exposed to the protein at a final concentration of 18 mM. ZmCORp inhibited the germination of conidia by 80%. A 50% decrease in mycelial growth resulted when germinated conidia were incubated with the protein. The partial characterization of ZmCORp suggests that this protein may play an important role in enhancing kernel resistance to A. flavus infection and aflatoxin accumulation.

Proteomic analysis of leaves from a diploid cybrid produced by protoplast fusion between Satsuma mandarin and pummelo

“…Lectins are proteins that recognize and specifically bind to glycoproteins, glycolipids, or polysaccarides, and they are often synthesized during seed development. Especially, Lectins play an important role in resistance to fungal infection and a various abiotic stress (Baker et al 2009;Lyou et al 2009). Another protein, acidic class II chitinase (spot 8), which was highly expressed in the HBP, was also a pathogenesis-related protein and could prevent fungal development by hydrolyzing fungal cell wall (Schlumbaum et al 1986).…”

Development of Maize Host Resistance to Aflatoxigenic Fungi

“…ZmCORp, a protein with a sequence similar to cold-regulated protein and identified in the above-proteomic studies, was shown to exhibit lectin-like hemagglutination activity against fungal conidia and sheep erythrocytes [71]. When tested against A. flavus, ZmCORp inhibited germination of conidia by 80% and decreased mycelial growth by 50%, when germinated conidia were incubated with the protein.…”

Developing Resistance to Aflatoxin in Maize and Cottonseed

“…A chitinase isolated from the maize inbred Tex6 was shown to inhibit the growth of A. flavus by 50% at a concentration of 20 μg/mL, however the gene encoding the chitinase has yet to be cloned [39]. Proteomics of maize kernel proteins also identified a protein, ZmCORp, that was present at higher levels in a resistant line of maize compared to levels in a sensitive line [67]. The protein demonstrated homology to cold-regulated proteins and recombinant ZmCORp exhibited lectin-like hemagglutination activity against fungal conidia and sheep erythrocytes.…”