Browsing by Author "Gilbert, Matthew K."

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    Carbon dioxide mediates the response to temperature and water activity levels in Aspergillus flavus during infection of maize kernels
    (MDPI, 2017-12-22) Gilbert, Matthew K.; Medina-Vayá, Ángel; Mack, Brian M.; Lebar, Matthew D.; Rodriguez, Alicia; Bhatnagar, Deepak; Magan, Naresh; Obrian, Gregory; Payne, Gary
    Aspergillus flavus is a saprophytic fungus that may colonize several important crops, including cotton, maize, peanuts and tree nuts. Concomitant with A. flavus colonization is its potential to secrete mycotoxins, of which the most prominent is aflatoxin. Temperature, water activity (aw) and carbon dioxide (CO2) are three environmental factors shown to influence the fungus-plant interaction, which are predicted to undergo significant changes in the next century. In this study, we used RNA sequencing to better understand the transcriptomic response of the fungus to aw, temperature, and elevated CO2 levels. We demonstrate that aflatoxin (AFB1) production on maize grain was altered by water availability, temperature and CO2. RNA-Sequencing data indicated that several genes, and in particular those involved in the biosynthesis of secondary metabolites, exhibit different responses to water availability or temperature stress depending on the atmospheric CO2 content. Other gene categories affected by CO2 levels alone (350 ppm vs. 1000 ppm at 30 °C/0.99 aw), included amino acid metabolism and folate biosynthesis. Finally, we identified two gene networks significantly influenced by changes in CO2 levels that contain several genes related to cellular replication and transcription. These results demonstrate that changes in atmospheric CO2 under climate change scenarios greatly influences the response of A. flavus to water and temperature when colonizing maize grain.
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    Interactions between water activity and temperature on the Aspergillus flavus transcriptome and aflatoxin B1 production
    (Elsevier, 2017-05-26) Medina-Vayá, Ángel; Gilbert, Matthew K.; Mack, Brian M.; OBrian, Gregory R.; Rodriguez, Alicia; Bhatnagar, Deepak; Payne, Gary; Magan, Naresh
    Effects of Aspergillus flavus colonization of maize kernels under different water activities (aw; 0.99 and 0.91) and temperatures (30, 37 °C) on (a) aflatoxin B1 (AFB1) production and (b) the transcriptome using RNAseq were examined. There was no significant difference (p = 0.05) in AFB1 production at 30 and 37 °C and 0.99 aw. However, there was a significant (p = 0.05) increase in AFB1 at 0.91 aw at 37 °C when compared with 30 °C/0.99 aw. Environmental stress effects using gene ontology enrichment analysis of the RNA-seq results for increasing temperature at 0.99 and 0.91 aw showed differential expression of 2224 and 481 genes, respectively. With decreasing water availability, 4307 were affected at 30 °C and 702 genes at 37 °C. Increasing temperature from 30 to 37 °C at both aw levels resulted in 12 biological processes being upregulated and 9 significantly downregulated. Decreasing aw at both temperatures resulted in 22 biological processes significantly upregulated and 25 downregulated. The interacting environmental factors influenced functioning of the secondary metabolite gene clusters for aflatoxins and cyclopiazonic acid (CPA). An elevated number of genes were co-regulated by both aw and temperature. An interaction effect for 4 of the 25 AFB1 genes, including regulatory and transcription activators occurred. For CPA, all 5 biosynthetic genes were affected by aw stress, regardless of temperature. The molecular regulation of A. flavus in maize is discussed.