Abstract
The striatin-interacting phosphatase and kinase (STRIPAK) complex is composed of striatin, protein phosphatase PP2A and protein kinases that regulate development in animals and fungi. In the filamentous ascomycete Sordaria macrospora, it is required for fruiting-body development and cell fusion. Here, we report on the presence and function of STRIPAK-associated kinases in ascomycetes. Using the mammalian germinal center kinases (GCKs) MST4, STK24, STK25 and MINK1 as query, we identified the two putative homologs SmKIN3 and SmKIN24 in S. macrospora. A BLASTP search revealed that both kinases are conserved among filamentous ascomycetes. The physical interaction of the striatin homolog PRO11 with SmKIN3 and SmKIN24 were verified by yeast two-hybrid (Y2H) interaction studies and for SmKIN3 by co-Immunoprecipitation (co-IP). In vivo localization found that both kinases were present at the septa and deletion of both Smkin3 and Smkin24 led to abnormal septum distribution. While deletion of Smkin3 caused larger distances between adjacent septa and increased aerial hyphae, deletion of Smkin24 led to closer spacing of septa and to sterility. Although phenotypically distinct, both kinases appear to function independently because the double-knockout strain ΔSmkin3/ΔSmkin24 displayed the combined phenotypes of each single-deletion strain.
Highlights
In filamentous fungi, the development of multicellular fruiting bodies requires highly conserved differentiation processes and is essential for sexual reproduction [1]
No striatin-interacting phosphatase and kinase (STRIPAK)-associated kinases have been identified in filamentous fungi (Fig 1)
Two variants have been reported for the N. crassa NCU04096 protein: a long version resulting from a transcript after splicing of three introns, and a short version derived from a transcript retaining intron 3 and following initiation of translation at a downstream ATG codon
Summary
The development of multicellular fruiting bodies requires highly conserved differentiation processes and is essential for sexual reproduction [1]. The filamentous ascomycete Sordaria macrospora is a well-established model organism for studying this process [2, 3]. S. macrospora is a haplont with a homothallic life style and does not require a mating partner for sexual reproduction [4]. In contrast to many other filamentous ascomycetes, S. macrospora produces no asexual spores [5]. The life cycle begins with the germination of PLOS ONE | DOI:10.1371/journal.pone.0139163. The life cycle begins with the germination of PLOS ONE | DOI:10.1371/journal.pone.0139163 September 29, 2015
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