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ARS Home » Southeast Area » New Orleans, Louisiana » Southern Regional Research Center » Food and Feed Safety Research » Research » Publications at this Location » Publication #418522
Research Project: Aflatoxin Control through Identification of Intrinsic and Extrinsic Factors Governing the Aspergillus Flavus-Corn Interaction

Location: Food and Feed Safety Research

Title: The Aspergillus flavus hacA Gene in the Unfolded Protein Response Pathway Is a Candidate Target for Host-Induced Gene Silencing

Author
item Chang, Perng Kuang

Submitted to: The Journal of Fungi
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/11/2024
Publication Date: 10/16/2024
Citation: Chang, P. 2024. The Aspergillus flavus hacA Gene in the Unfolded Protein Response Pathway Is a Candidate Target for Host-Induced Gene Silencing. The Journal of Fungi. 10(10). Article 719. https://doi.org/10.3390/jof10100719.
DOI: https://doi.org/10.3390/jof10100719

Interpretive Summary: The fungus, Aspergillus flavus, is a plant pathogen and infects corn, cottonseed, peanut, and tree nuts. It produces highly toxic and carcinogenic aflatoxins that are harmful to human and animal health. Significant economic losses have resulted from aflatoxin contamination of food and feed. Three major intervention technologies are currently employed: good agricultural practices, crop resistance breeding and biological control. This study characterized a regulatory gene that maintains cellular protein balance levels , which are critical to the fungus’ growth and development. The gene has the potential to be used in the engineering of crop resistance against fungal infection and thus reduce aflatoxin contamination.

Technical Abstract: Fungal HacA/Hac1 transcription factors regulate unfolded protein response (UPR). Cells use UPR to control endoplasmic reticulum (ER) protein homeostasis, which is critical to growth, development and virulence. In this study, Aspergillus flavus HacA functional domains were dissected by CRISPR/Cas9 to reveal the relationship between genotype and phenotype. Changes in hacA encoding basic/acidic amino acid-rich (Bsc) and basic leucine zipper (bZIP) domains in regenerated transformants were exclusively in-frame. Total transformant numbers of the experimental sets were found to be only up to16% of the controls. These results suggest that out-of-frame mutations in Bsc- and bZIP-coding sequences are lethal. Changes in the non-conventional intron included primarily out-of-frame insertions and deletions. The transformant survival rate also was low at about 7%. Beside conidial morphology, sclerotial, mixed (conidial and sclerotial), and mycelial colony morphologies, were observed among the mutants. An ER stress test with dithiothreitol showed that the sclerotial and the mycelial mutants were much more sensitive than the conidial mutants. The mycelial mutants were unable to produce aflatoxin but still produced aspergillus acid and kojic acid. RNAi experiments with a hacA sequence region encompassing the Bsc- and bZIP domains showed that transformant survival rates were generally decreased; a small portion of transformants displayed phenotypic changes. Hence, A. flavus hacA may be considered a candidate target for future host-induced gene silencing to control infection and aflatoxin contamination of crops.