Department of Medical Biotechnology, Soonchunhyang University, Asan, 336-745, Republic of Korea,
J Microbiol. 2013 Dec;51(6):814-20. doi: 10.1007/s12275-013-3465-2. Epub 2013 Dec 19.
Homothallic Didymella zeae-maydis undergoes sexual reproduction by selfing. Sequence analysis of the mating type (MAT) locus from this fungus revealed that MAT carries both MAT1-1-1 and MAT1-2-1 genes found in heterothallic Dothideomycetes, separated by ∼1.0 kb of noncoding DNA. To understand the mechanistic basis of homothallism in D. zeae-maydis, each of the MAT genes was deleted and the effects on selfing and on ability to cross in a heterothallic manner were determined. The strain carrying an intact MAT1-1-1 but defective MAT1-2-1 gene (MAT1-1-1;ΔMAT1-2-1) was self-sterile, however strains carrying an intact MAT1-2-1 but defective MAT1-1-1 gene (ΔMAT1-1-1;MAT1-2-1), when selfed, showed delayed production of a few ascospores. Attempts to cross the two MAT deletion strains yielded fewer ΔMAT1-1-1;MAT1-2-1 than MAT1-1-1;ΔMAT1-2-1 progeny and very few ascospores overall compared to WT selfs. This study demonstrates that, as in the other homothallic Dothideomycetes, both MAT genes are required for full fertility, but that, in contrast to other cases, the presence of a single MAT1-2-1 gene can induce homothallism, albeit inefficiently, in D. zeae-maydis.
同质结合的玉米赤霉菌通过自交进行有性繁殖。对该真菌交配型（MAT）基因座的序列分析表明，MAT 携带了在异质结合的子囊菌中发现的 MAT1-1-1 和 MAT1-2-1 基因，它们被约 1.0 kb 的非编码 DNA 隔开。为了了解玉米赤霉菌同质结合的机制基础，我们删除了每个 MAT 基因，并确定了它们对自交和异质交配能力的影响。携带完整 MAT1-1-1 但 MAT1-2-1 基因缺陷的菌株（MAT1-1-1;ΔMAT1-2-1）是自不育的，然而携带完整 MAT1-2-1 但 MAT1-1-1 基因缺陷的菌株（ΔMAT1-1-1;MAT1-2-1）在自交时，仅产生少量延迟产生的子囊孢子。试图将这两个 MAT 缺失菌株杂交，得到的 ΔMAT1-1-1;MAT1-2-1 后代比 MAT1-1-1;ΔMAT1-2-1 后代少，与 WT 自交相比，总的来说子囊孢子也很少。这项研究表明，与其他同质结合的子囊菌一样，两个 MAT 基因都需要完全的育性，但与其他情况不同的是，单个 MAT1-2-1 基因的存在可以诱导玉米赤霉菌的同质结合，尽管效率不高。
