Unexpected placement of the MAT1-1-2 gene in the MAT1-2 idiomorph of Thielaviopsis

Abstract

Sexual reproduction in the Ascomycota is controlled by genes encoded at the mating-type or MAT1 locus. The two allelic versions of this locus in heterothallic species, referred to as idiomorphs, are defined by the MAT1-1-1 (for the MAT1-1 idiomorph) and MAT1-2-1 (for the MAT1-2 idiomorph) genes. Both idiomorphs can contain additional genes, although the contents of each is typically specific to and conserved within particular Pezizomycotina lineages. Using full genome sequences, complemented with conventional PCR and Sanger sequencing, we compared the mating-type idiomorphs in heterothallic species of Thielaviopsis (Ceratocystidaceae). The analyses showed that the MAT1-1 idiomorph of T. punctulata, T. paradoxa, T. euricoi, T. ethacetica and T. musarum harboured only the expected MAT1-1-1 gene. In contrast, the MAT1-2 idiomorph of T. punctulata, T. paradoxa and T. euricoi encoded the MAT1-2-1, MAT1-2-7 and MAT1-1-2 genes. Of these, MAT1-2-1 and MAT1-2-7 are genes previously reported in this idiomorph, while MAT1-1-2 is known only in the MAT1-1 idiomorph. Phylogenetic analysis showed that the Thielaviopsis MAT1-1-2 groups with the known homologues of this gene in other Microascales, thus confirming its annotation. Previous work suggests that MAT1-1-2 is involved in fruiting body development, a role that would be unaffected by its idiomorphic position. This notion is supported by our findings for the MAT1 locus structure in Thielaviopsis species. This also serves as the first example of a MAT1-1-specific gene restricted to only the MAT1-2 idiomorph.

Draft genome sequence of Annulohypoxylon stygium, Aspergillus mulundensis, Berkeleyomyces basicola (syn. Thielaviopsis basicola), Ceratocystis smalleyi, two Cercospora beticola strains, Coleophoma cylindrospora, Fusarium fracticaudum, Phialophora cf. hyalina, and Morchella septimelata

“…5 ; Molano et al 2018 , Van der Nest et al 2014a , b , Wilken et al 2013 , Wingfield et al 2015b , 2016b ). In addition, published genome sequences are available for five Huntiella species ( Van der Nest et al 2014a , b , 2015 , Wingfield et al 2016b , 2017 ), two Endoconidiophora species ( Wingfield et al 2016a ), three isolates representing two Thielaviopsis species ( Wilken et al 2018 , Wingfield et al 2015a ; Wingfield et al 2015b ), one Davidsoniella species ( Wingfield et al 2015b ), one Bretziella species (previously Ceratocystis fagacearum ; De Beer et al 2017 , Wingfield et al 2016b ), one Ambrosiella species ( Vanderpool et al 2017 ) as well as for C. adiposa ( Wingfield et al 2016a ). This brings the number of published Ceratocystidaceae genomes to 21, with the genome assemblies of several others publicly available ( www.ncbi.nlm.nih.gov/assembly/?term=ceratocystidaceae ).…”

“…The Benchmarking Universal Single-Copy Orthologs (BUSCO v. 1.22) tool was used in combination with the fungal data set to provide a quantitative measure of the level of genome completeness ( Simão et al 2015 ). The 60S, LSU and MCM7 gene regions were extracted from the genome and, together with these regions from the recently sequenced species C. cacaofunesta ( Molano et al 2018 ), T. punctulata isolate CMW1032 ( Wilken et al 2018 ), H. savannae ( Van der Nest et al 2015 ) and A. xylebori ( Vanderpool et al 2017 ) were added to the Ceratocystidaceae dataset used for phylogenetic analysis by Wingfield et al . (2017) .…”

“…In this study, we aimed to produce a draft genome assembly for C. smalleyi . This assembly would be the seventh Ceratocystis species for which a genome sequence is published, and adds to the valuable genomic resource available for members of Ceratocystidaceae ( Molano et al 2018 , Van der Nest et al 2014a , b , 2015 , Vanderpool et al 2017 , Wilken et al 2013 , 2018 , Wingfield et al 2015a , b , 2016a , b ). Furthermore, the availability of a genome assembly will afford the opportunity in future to investigate aspects of the unique biology of C. smalleyi .…”

IMA genome - F14

“…Much work has been focussed on sexual reproduction in the family (e.g. Wilken et al 2017 ; Nel et al 2018 ; Simpson et al 2018 ), and the availability of two genome sequences for putatively asexual members will be a valuable addition to this ongoing project. Together with the Ch.…”

Black root rot: a long known but little understood disease

“…The contemporary availability of whole genome sequences for fungi has led to the discovery that various plant pathogens, originally thought to be asexual, harbour the genes required for sexual reproduction. Examples are readily found in species of the Ceratocystidaceae, including species of Thielaviopsis (Wilken et al ., ), Huntiella (Wilson et al ., ) and Ceratocystis (Wilken et al ., ). However, many of these species do not conform to the conventional homothallic or heterothallic mating system, but use secondary homothallic strategies such as mating type switching (Witthuhn et al ., ; Wilken et al ., ) and unisexuality (Wilson et al ., ,b).…”