The sexual spore pigment asperthecin is required for normal ascospore production and protection from UV light in Aspergillus nidulans

Abstract

Many fungi develop both asexual and sexual spores that serve as propagules for dissemination and/or recombination of genetic traits. Asexual spores are often heavily pigmented and this pigmentation provides protection from UV light. However, little is known about any purpose pigmentation that may serve for sexual spores. The model Ascomycete Aspergillus nidulans produces both green pigmented asexual spores (conidia) and red pigmented sexual spores (ascospores). Here we find that the previously characterized red pigment, asperthecin, is the A. nidulans ascospore pigment. The asperthecin biosynthetic gene cluster is composed of three genes: aptA, aptB, and aptC, where deletion of either aptA (encoding a polyketide synthase) or aptB (encoding a thioesterase) yields small, mishappen hyaline ascospores; while deletion of aptC (encoding a monooxygenase) yields morphologically normal but purple ascospores. ∆aptA and ∆aptB but not ∆aptC or wild type ascospores are extremely sensitive to UV light. We find that two historical ascospore color mutants, clA6 and clB1, possess mutations in aptA and aptB sequences, respectively.

Evaluating the contribution of historical and contemporary temperature to the oospore production of self‐fertile Phytophthora infestans

“…On the other hand, the observed pattern of altitudinal distribution in oospore production may be generated by the interaction between UV and thermal adaptation. It is widely believed that UV radiation induces sexual reproduction in mycelial pathogen (Palmer et al., 2021 ). As altitude increases, UV radiation increases but air temperature decreases (Blumthaler et al., 1992 ).…”

Comparative Genomics of Three Aspergillus Strains Reveals Insights into Endophytic Lifestyle and Endophyte-Induced Plant Growth Promotion

“…In addition, the three endophytes all possess gene clusters involved in the synthesis of asperthecin. The ascosporous pigment of A. nidulans is reportedly formed by asperthecin, and the asperthecin biosynthetic gene cluster consists of three genes, aptA, aptB, and aptC, in which the deletion of aptA (encoding polyketide synthase) or aptB (encoding thioesterase) produces small, malformed transparent ascospores, whereas the deletion of aptC (encoding a monooxygenase) produces morphologically normal but purple ascospores [ 87 ]. These results suggested that the asperthecin biosynthetic gene clusters of the three endophytes are important to maintaining normal spore morphology and successfully colonizing rice roots.…”