Division of Biological Sciences, Institute for Basic Sciences, Institute of Bioactive Materials, Chonbuk National University, Jeonju, 561-756, Republic of Korea.
J Microbiol. 2011 Jun;49(3):418-30. doi: 10.1007/s12275-011-0193-3. Epub 2011 Jun 30.
Two genes encoding MAP kinase homologs, designated as mpkB and mpkC, were isolated from Aspergillus nidulans by PCR with degenerate primers. Deletion and over-expression mutants of mpkC showed no detectable phenotypes under any external stress tested. Deletion of mpkB caused pleiotropic phenotypes including a failure in forming cleistothecia under any induction conditions for sexual development, increased Hülle cell production, slow hyphal growth and aberrant conidiophore morphology. Over-expression of mpkB led to increased cleistothecium production. While the transcripts of mpkB and mpkC were constitutively synthesized through the entire life cycle, their size and amount differed with developmental stages. An outcross test using fluorescent protein reporters showed that the mpkB deletion mutant could not form heterokaryons with wild type. Protoplast fusion experiments showed that the fusant of the mpkB mutant with wild type could undergo normal sexual development. However, heterokaryotic mycelia that were produced from a fusant between two mpkB deletion mutants could not form cleistothecia, although they did appear to form diploid nuclei. These results suggest that the MpkB MAP kinase is required for some post-karyogamy process as well as at the hyphal anastomosis stage to accomplish sexual development successfully.
两个编码 MAP 激酶同源物的基因，分别命名为 mpkB 和 mpkC，通过用简并引物的 PCR 从构巢曲霉中分离得到。mpkC 的缺失和过表达突变体在任何测试的外部应激条件下均未表现出可检测的表型。mpkB 的缺失导致了包括在任何有性发育诱导条件下无法形成闭囊壳在内的多种表型缺陷，增加了 Hülle 细胞的产生，菌丝生长缓慢，分生孢子梗形态异常。mpkB 的过表达导致闭囊壳产量增加。虽然 mpkB 和 mpkC 的转录本在整个生命周期中持续合成，但它们的大小和数量随发育阶段而不同。使用荧光蛋白报告基因的杂交试验表明，mpkB 缺失突变体不能与野生型形成异核体。原生质体融合实验表明，mpkB 突变体与野生型的融合体可以进行正常的有性发育。然而，来自两个 mpkB 缺失突变体之间融合体的异核菌丝体不能形成闭囊壳，尽管它们似乎确实形成了二倍体核。这些结果表明，MpkB MAP 激酶对于某些核后过程以及在菌丝体吻合阶段成功完成有性发育是必需的。
