|LINDO, LAURA - University Of Leon|
|CARDOZA, ROSA - University Of Leon|
|GUTIERREZ, SANTIAGO - University Of Leon|
Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 3/17/2019
Publication Date: 3/17/2019
Citation: Proctor, R., McCormick, S.P., Lindo, L., Cardoza, R.E., Kim, H.-S., Brown, D.W., Busman, M., Gutierrez, S. 2019. Convergence and divergence of gene function during the evolutionary history of trichothecene biosynthesis [abstract].
Technical Abstract: Trichothecenes are a family of terpenoid toxins produced by some species in at least 11 genera of fungi, including plant pathogens, insect pathogens and saprotrophs. Collectively, these fungi produce over 150 trichothecene analogs that have the same multicyclic core structure but vary in patterns of substituents attached to the core structure. Three decades of genetic analyses have identified 18 trichothecene biosynthetic (TRI) genes that account for most of the variation in substituents. However, recent comparative genomic analyses of trichothecene-producing fungi have led to the identification of additional genes that are predicted to be involved in trichothecene biosynthesis because of their location near other TRI genes and their pattern of expression. Here, functional characterization of three of these genes (TRI18, TRI23, TRI24) provided evidence for their specific roles in trichothecene biosynthesis. TRI18, which was found in most trichothecene-producing fungi, is part of a novel acylation mechanism at carbon 4 (C4) that involves two, sequentially-acting acyltransferases (Tri3 and Tri18). By contrast, in fungi that lack TRI18, Tri3 appears to act alone and at C15 rather than C4. TRI23, which was found only in some Trichoderma species, likely catalyzes modification of an 8-carbon polyketide to form the acyl substrate for Tri18. The function of TRI24, which was found only in Aspergillus hancockii and Microcyclospora tardicrescens, demonstrates the existence of a trichothecene-C8-hydroxylase gene that is different from a previously identified C8-hydroxylase gene in Fusarium. These results provide novel insights into the trichothecene biosynthetic pathway and indicate that the evolutionary history of the pathway has included both convergence and divergence of gene function.