The mating-related loci sexM and sexP of the zygomycetous fungus Mucor mucedo and their transcriptional regulation by trisporoid pheromones

Abstract

The putative mating type locus of mucoralean fungi consists of a single high mobility group (HMG)-domain transcription factor gene, sexM or sexP, flanked by genes for an RNA helicase and a triosephosphate transporter. We used degenerate primers derived from the amino acid sequence of the RNA helicase to sequence a fragment of this gene from Mucor mucedo. This fragment was extended by inverse PCR to obtain the complete sequences of the sex loci from both mating types of M. mucedo. The sex loci in M. mucedo reflect the general picture obtained previously for Phycomyces blakesleeanus, presenting a single HMG-domain transcription factor gene, sexM and sexP in the minus and plus mating types, respectively. These are located next to a gene for RNA helicase. Transcriptional analysis by quantitative real-time PCR showed that only transcription of sexM is considerably stimulated by adding trisporoid pheromones, thus mimicking sexual stimulation, whereas sexP is only slightly affected. These differences in regulation between sexM and sexP are supported by the observation that the promoter sequences controlling these genes show no similarities. The protein structures themselves are considerably different. The SexM, but not the SexP protein harbours a nuclear localization sequence. The SexM protein is indeed transported to nuclei. This was shown by means of a GFP fusion construct that was used to study the localization of SexM in the yeast Saccharomyces cerevisiae. The fusion protein is highly enriched in nuclei.

Early and Late Trisporoids Differentially Regulate β-Carotene Production and Gene Transcript Levels in the Mucoralean Fungi Blakeslea trispora and Mucor mucedo

“…For the future, it is necessary to establish the genetic basis of differences between the plus and minus strains in response to individual trisporoids. M. mucedo treated with trisporoid stimulants had higher transcript levels of sexM than of sexP (25). Parallel studies in B. trispora and other members (including homothallic ones) of the order Mucorales will promote the elucidation of genetic variations and contrasts among partners that are otherwise morphologically indistinguishable.…”

“…Few enzymes are known so far, such as 4-dihydromethyltrisporate dehydrogenase (TSP1), 4-dihydrotrisporin dehydrogenase (TSP2) (20)(21)(22), and a putative esterase enzyme from the minus partner that converts methyl trisporate to trisporic acids in both homothallic Mucorales (Zygorhynchus moelleri) and heterothallic Mucorales (23). The high-mobility group (HMG) transcription factor genes sexM and sexP are associated with the minus and plus mating-type loci in P. blakesleeanus and M. mucedo (24,25). Technically, it is difficult to carry out functional gene analyses via classical genetic approaches in either B. trispora or M. mucedo without sequenced genome data.…”

Diversity, ecology, and evolution in Phycomyces

“…The transcript level of gene sexM in M. mucedo increases in mated cultures of strains of opposite sex and upon exposure to a mixture of trisporoids; the same occurs to a lesser extent with sexP (Wetzel et al 2012). Sexual development is accompanied by modified levels of the transcripts of several hundred genes in mated cultures (Kuzina et al 2008).…”

“…The (þ) and (À) allelomorphs contain a gene, sexP and sexM, respectively, similar to those found in other Mucorales: Mucor circinelloides (Lee et al 2008), Rhizopus oryzae (Gryganskyi et al 2010), Syzygites megalocarpus (Idnurm 2011a), and Mucor mucedo (Wetzel et al 2012). Gene sexM is necessary for mating, but not for vegetative growth in M. circinelloides (Li et al 2011).…”

“…The capitalized nucleotides are conserved in P. blakesleeanus, Mucor mucedo, Mucor circinelloides, and R. oryzae (Wetzel et al 2012). This motif was not found in B. trispora.…”