Cladosporium cladosporioides LPSC 1088 Produces the 1,8-Dihydroxynaphthalene-Melanin-Like Compound and Carries a Putative pks Gene

Cladosporium cladosporioides is a dematiaceous fungus with coloured mycelia and conidia due to the presence of dark pigments. The purpose of this study was to characterize the dark pigments synthetized by Cladosporium sp. LPSC no. 1088 and also to identify the putative polyketide synthase (pks) gene that might be involved in the pigment biosynthesis. Morphological as well as molecular features like the ITS sequence confirmed that LPSC 1088 is Cladosporium cladosporioides. UV-visible, Fourier Transform Infrared (FTIR) and Electron Spin Resonance (ESR) spectroscopy analysis as well as melanin inhibitors suggest that the main dark pigment of the isolate was 1,8 dihydroxynaphthalene (DHN)-melanin-type compound. Two commercial fungicides, Difenoconazole and Chlorothalonil, inhibited fungal growth as well as increased pigmentation of the colonies suggesting that melanin might protect the fungus against chemical stress. The pigment is most probably synthetized by means of a pentaketide pathway since the sequence of a 651?bp fragment, coding for a putative polyketide synthase, is highly homologous to pks sequences from other fungi.     

A scytalone dehydratase gene from<Emphasis Type="Italic"> Ophiostoma floccosum</Emphasis> restores the melanization and pathogenicity phenotypes of a melanin-deficient<Emphasis Type="Italic"> Colletotrichum lagenarium</Emphasis> mutant

Scytalone dehydratase is involved in the production of fungal dihydroxynaphthalene (DHN) melanin. We have isolated and characterized OSD1, a gene encoding scytalone dehydratase from the sap-staining fungus Ophiostoma floccosum by PCR-based cloning. Sequence analysis suggests that the OSD1 gene encodes a protein of 216 amino acids with a molecular weight of 24.2 kDa that shows 51-70% sequence identity to other scytalone dehydratases. The cloned OSD1 contains two introns of 76 bp and 63 bp in length, and is the longest scytalone dehydratase gene sequence so far reported. Transformation of a DHN melanin-deficient, non-pathogenic, mutant of Colletotrichum lagenarium with the OSD1 gene restored melanin production and pathogenicity. The ability of the mutant to produce the OSD1 gene product was confirmed by RT-PCR analysis. These data show that the cloned OSD1 gene product can function in the DHN melanin biosynthetic pathway in C. lagenarium.     

植物病原真菌1,8-间苯二酚黑色素研究进展

黑色素是一种广泛分布于生物体中的酚类聚合物疏水色素,分为1,8-间苯二酚(1,8-dihydroxynaphthalene,DHN)黑色素和3,4-二羟基苯丙氨酸(3,4-dihydroxyphenylalanine,L-DOPA)黑色素两种,其中DHN黑色素多存在于子囊菌门的植物病原真菌中。基因组和转录组技术的发展及功能基因组研究的深入,使DHN黑色素合成途径上关键基因在不同病原真菌中被鉴定,而且黑色素与真菌抗逆、发育和致病的关系受到越来越多的关注。本文阐述了DHN黑色素合成途径及其在真菌抗辐射与抗极端温度中的作用,以及黑色素对真菌侵染和细胞发育的影响,旨在加深人们对黑色素介导真菌与环境和寄主协同进化的认识,这对黑色素的基础研究和开发利用具有重要意义。     

Cross-species microarray hybridization to identify developmentally regulated genes in the filamentous fungus <Emphasis Type="Italic">Sordaria macrospora</Emphasis>

The filamentous fungus Sordaria macrospora forms complex three-dimensional fruiting bodies that protect the developing ascospores and ensure their proper discharge. Several regulatory genes essential for fruiting body development were previously isolated by complementation of the sterile mutants pro1, pro11 and pro22. To establish the genetic relationships between these genes and to identify downstream targets, we have conducted cross-species microarray hybridizations using cDNA arrays derived from the closely related fungus Neurospora crassa and RNA probes prepared from wild-type S. macrospora and the three developmental mutants. Of the 1,420 genes which gave a signal with the probes from all the strains used, 172 (12%) were regulated differently in at least one of the three mutants compared to the wild type, and 17 (1.2%) were regulated differently in all three mutant strains. Microarray data were verified by Northern analysis or quantitative real time PCR. Among the genes that are up- or down-regulated in the mutant strains are genes encoding the pheromone precursors, enzymes involved in melanin biosynthesis and a lectin-like protein. Analysis of gene expression in double mutants revealed a complex network of interaction between the pro gene products.