Abstract
Aspergillus flavus is a common saprophytic filamentous fungus that produces the highly toxic natural compound aflatoxin during its growth process. Synthesis of the aflatoxins, which can contaminate food crops causing huge losses to the agricultural economy, is often regulated by epigenetic modification, such as the histone acetyltransferase. In this study, we used Aspergillus flavus as an experimental model to construct the acetyltransferase gene rtt109 knockout strain (△rtt109) and its complementary strain (△rtt109·com) by homologous recombination. The growth of △rtt109 was significantly suppressed compared to the wild type (WT) strain and the △rtt109·com strain. The sclerotium of △rtt109 grew smaller, and the amount of sclerotia generated by △rtt109 was significantly reduced. The number of conidiums of △rtt109 was significantly reduced, especially on the yeast extract sucrose (YES) solid medium. The amount of aflatoxins synthesized by △rtt109 in the PDB liquid medium was significantly decreased We also found that the △rtt109 strain was extremely sensitive to DNA damage stress. Through the maize seed infection experiment, we found that the growth of △rtt109 on the surface of affected corn was largely reduced, and the amount of aerial mycelium decreased significantly, which was consistent with the results on the artificial medium. We further found that H3K9 was the acetylated target of Rtt109 in A. flavus. In conclusion, Rtt109 participated in the growth, conidium formation, sclerotia generation, aflatoxin synthesis, environmental stress response, regulation of infection of A. flavus. The results from this study of rtt109 showed data for acetylation in the regulation of life processes and provided a new thought regarding the prevention and control of A. flavus hazards.
Highlights
In eukaryotic organisms, chromatin is a dynamic and highly regulated structure that functions in compacting DNA into the nucleus and affects vital functions, such as gene expression, cell differentiation, and cell division
A BLAST search and phylogenetic analysis revealed that regulator of Ty1 transposition 109 (Rtt109) or its homologous proteins were found in Saccharomyces cerevisiae, Aspergillus niger, Aspergillus flavus, Aspergillus fumigatus, Aspergillus nidulans, Zea mays, Arabidopsis thaliana, Dorsophilia melanogaster, Mus musculus, and Homo sapiens (Fig. 1a)
Rtt109 is a typical B-type histone acetyltransferases (HATs) predominantly localized in vacuoles or vesicles There are two types of intracellular HATs, including A-type HATs for acetyltransferases localized and functioning in the nucleus, and B-type HATs for acetyltransferases predominantly existing in intracytoplasmic regions, which are transported into the nucleus to function
Summary
Chromatin is a dynamic and highly regulated structure that functions in compacting DNA into the nucleus and affects vital functions, such as gene expression, cell differentiation, and cell division. HATs interacting with acetyl-coenzyme A, a co-factor that transfers an acetyl-group to a lysine residue, allows chromatin to transform into a flexible structure, and thereby activate transcription (Shahbazian & Grunstein, 2007). HDACs deacetylate acetylated-lysine residues, compress DNA sequences, and lead to transcription repression (Kouzarides, 2000). There is more evidence implicating that the acetylation on histone residues plays an important role for many cellular physiological processes in eukaryotes. Gcn, a KAT2-family HAT (Carrozza et al, 2003), was reported to participate in the regulation of nearly 12% of the genome in yeast (Lee et al, 2000). In spite of the acetylation of histone and the functions of relative HATs have been studied extensively, there are still many functions that have not been fully characterized in fungi
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