Title The MpkB MAP Kinase Plays a Role in Post-karyogamy Processes as well as in Hyphal Anastomosis During Sexual Development in Aspergillus nidulans
Author Sang-Cheol Jun1, Sei-Jin Lee2, Hyun-Joo Park1, Ji-Young Kang1, Young-Eun Leem1, Tae-Ho Yang1, Mi-Hee Chang1, Jung-Mi Kim1, Seung-Hwan Jang1, Hwan-Gyu Kim1, Dong-Min Han3, Keon-Sang Chae1, and Kwang-Yeop Jahng1*
Address 1Division of Biological Sciences, Institute for Basic Sciences, Institute of Bioactive Materials, Chonbuk National University, Jeonju 561-756, Republic of Korea, 2Korea Basic Science Institute Jeonju Center, Wonkwang University, Iksan 570-749, Republic of Korea, 3Division of Life Sciences, Wonkwang University, Iksan 570-749, Republic of Korea
Bibliography Journal of Microbiology, 49(3),418-430, 2011,
Key Words Aspergillus nidulans, MpkB MAP kinase, Hülle cell, post-karyogamy, anastomosis
Abstract 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.