Protein O-mannosyltransferases (Pmts) initiate O-mannosyl glycan biosynthesis from Ser and Thr residues of target proteins. Fungal Pmts are divided into three subfamilies, Pmt1, -2, and -4. Aspergillus nidulans possesses a single representative of each Pmt subfamily, pmtA (subfamily 2), pmtB (subfamily 1), and pmtC (subfamily 4). In this work, we show that single ⌬pmt mutants are viable and have unique phenotypes and that the ⌬pmtA ⌬pmtB double mutant is the only viable double mutant. This makes A. nidulans the first fungus in which all members of individual Pmt subfamilies can be deleted without loss of viability. At elevated temperatures, all A. nidulans ⌬pmt mutants show cell wall-associated defects and increased sensitivity to cell wallperturbing agents. The ⌬pmt mutants also show defects in developmental patterning. Germ tube emergence is early in ⌬pmtA and more frequent in ⌬pmtC mutants than in the wild type. In ⌬pmtB mutants, intrahyphal hyphae develop. All ⌬pmt mutants show distinct conidiophore defects. The ⌬pmtA strain has swollen vesicles and conidiogenous cells, the ⌬pmtB strain has swollen conidiophore stalks, and the ⌬pmtC strain has dramatically elongated conidiophore stalks. We also show that AN5660, an ortholog of Saccharomyces cerevisiae Wsc1p, is modified by PmtA and PmtC. The ⌬pmt phenotypes at elevated temperatures, increased sensitivity to cell wall-perturbing agents and restoration to wild-type growth with osmoticum suggest that A. nidulans Pmts modify proteins in the cell wall integrity pathway. The altered developmental patterns in ⌬pmt mutants suggest that A. nidulans Pmts modify proteins that serve as spatial cues.
The acenaphthylene-degrading bacterium Rhizobium sp. strain CU-A1 was isolated from petroleum-contaminated soil in Thailand. This strain was able to degrade 600 mg/liter acenaphthylene completely within three days. To elucidate the pathway for degradation of acenaphthylene, strain CU-A1 was mutagenized by transposon Tn5 in order to obtain mutant strains deficient in acenaphthylene degradation. Metabolites produced from Tn5-induced mutant strains B1, B5, and A53 were purified by thin-layer chromatography and silica gel column chromatography and characterized by mass spectrometry. The results suggested that this strain cleaved the fused five-membered ring of acenaphthylene to form naphthalene-1,8-dicarboxylic acid via acenaphthenequinone. One carboxyl group of naphthalene-1,8-dicarboxylic acid was removed to form 1-naphthoic acid which was transformed into salicylic acid before metabolization to gentisic acid. This work is the first report of complete acenaphthylene degradation by a bacterial strain.
HighlightsEukaryotic protein O-mannosyltransferases (Pmts) are divided into three subfamilies (1, 2 and 4).The filamentous fungus Aspergillus nidulans has three Pmts, one from each subfamily.PmtA, PmtB and PmtC form heterodimers in all pairwise combinations.PmtC (subfamily 4) forms homodimers.
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