title: Unconventional Recombination in the Mating Type Locus of Heterothallic Apple Canker PathogenValsa mali.
abstract: Sexual reproduction in filamentous ascomycetes is controlled by the mating type (MAT) locus, including two idiomorphsMAT1-1andMAT1-2Understanding theMATlocus can provide clues for unveiling the sexual development and virulence factors for fungal pathogens. The genusValsa(Sordariomycetes, Diaporthales) contains many tree pathogens responsible for destructive canker diseases. The sexual stage of these ascomycetes is occasionally observed in nature, and noMATlocus has been reported to date. Here, we identified theMATlocus of the apple canker pathogenValsa mali, which causes extensive damage, and even death, to trees.V. maliis heterothallic in that each isolate carries either theMAT1-1orMAT1-2idiomorph. However, theMATstructure is distinct from that of many other heterothallic fungi in the Sordariomycetes. Two flanking genes,COX13andAPN2, were coopted into theMATlocus, possibly by intrachromosomal rearrangement. After the acquisition of foreign genes, unequal recombination occurred betweenMAT1-1/2idiomorphs, resulting in a reverse insertion in theMAT1-2idiomorph. Evolutionary analysis showed that the three completeMAT1-1-2,COX13, andAPN2genes in this region diverged independently due to different selection pressure. Null hypothesis tests of a 1:1MATratio of 86V. maliisolates from four different provinces showed a relatively balanced distribution of the two idiomorphs in the fields. These results provide insights into the evolution of the mating systems in Sordariomycetes.
authors.affiliation: State Key Laboratory of Crop Stress Biology for Arid Areas, College of Plant Protection, Northwest A&F University, Yangling, Shaanxi 712100, China.
authors.forename: Zhiyuan
authors.identifier: 0000-0002-7189-895X
authors.initials: Z
authors.lastname: Yin
authors.affiliation: State Key Laboratory of Crop Stress Biology for Arid Areas, College of Plant Protection, Northwest A&F University, Yangling, Shaanxi 712100, China.
authors.forename: Xiwang
authors.initials: X
authors.lastname: Ke
authors.affiliation: State Key Laboratory of Crop Stress Biology for Arid Areas, College of Plant Protection, Northwest A&F University, Yangling, Shaanxi 712100, China.
authors.forename: Zhengpeng
authors.initials: Z
authors.lastname: Li
authors.affiliation: State Key Laboratory of Crop Stress Biology for Arid Areas, College of Plant Protection, Northwest A&F University, Yangling, Shaanxi 712100, China.
authors.forename: Jiliang
authors.initials: J
authors.lastname: Chen
authors.affiliation: State Key Laboratory of Crop Stress Biology for Arid Areas, College of Plant Protection, Northwest A&F University, Yangling, Shaanxi 712100, China.
authors.forename: Xiaoning
authors.initials: X
authors.lastname: Gao
authors.affiliation: State Key Laboratory of Crop Stress Biology for Arid Areas, College of Plant Protection, Northwest A&F University, Yangling, Shaanxi 712100, China huanglili@nwsuaf.edu.cn.
authors.forename: Lili
authors.initials: L
authors.lastname: Huang
mesh_terms: D001203:Ascomycota / Q000235:genetics* / Q000648:ultrastructure; D001483:Base Sequence; D019143:Evolution, Molecular; D049770:Genes, Mating Type, Fungal; D027845:Malus / Q000382:microbiology*; D010802:Phylogeny; D010935:Plant Diseases / Q000235:genetics*; D011995:Recombination, Genetic; D013045:Species Specificity
keywords: Cytospora sp.; MAT; sexual reproduction; unequal recombination