Distribution and bioinformatic analysis of the cerato-platanin protein family in Dikarya

The cerato-platanin family is a group of small cysteine-rich fungal proteins new to science. They usually are abundantly secreted extracellularly and are involved in fungus-host interactions. With the advance of available fungal genome sequences, we performed a genomewide study of the distribution of this family in fungi and analyzed the common characteristics of the protein sequences. A total of 55 fungal genomes, including 27 from Ascomycota and 28 from Basidiomycota, were used. A total of 130 cerato-platanin homolog protein sequences were obtained and analyzed. Our results showed that cerato-platanin homologs existed in both Ascomycota and Basidiomycota but were lost in early branches of jelly fungi as well as in some groups with yeast or yeast-like forms in their life cycle. Homolog numbers varied considerably between Ascomycota and Basidiomycota. Phylogenetic analysis suggested that the ancestor of the Dikarya possessed multiple copies of cerato-platanins, which sorted differently in Ascomycota and Basidiomycota, and that this gene family might have expanded in the Basidiomycota. Almost all homologs contained signal peptide sequences, and the length of mature proteins were mainly 105-134 amino acids. Four cysteines involved in forming two disulfide bridges and signature sequences (CSD or CSN) were highly conserved in most homologs. These results indicated a higher diversity of the cerato-platanin family in Basidiomycota than Ascomycota.

角-Platanin（cerato-platanin）家族是一类学界新近发现的富含半胱氨酸的小型真菌蛋白质家族。该家族蛋白通常会大量分泌至胞外，并参与真菌与宿主的互作过程。随着真菌基因组序列数据的不断丰富，本研究开展了该家族在真菌界中的全基因组分布分析，并对其蛋白序列的共性特征进行了系统解析。本研究共纳入55个真菌基因组，其中子囊菌门（Ascomycota）27个、担子菌门（Basidiomycota）28个，最终获得并分析了130条角-Platanin同源蛋白序列。研究结果显示，角-Platanin同源蛋白广泛存在于子囊菌门与担子菌门中，但在胶质真菌的早期演化分支以及部分生活史中存在酵母或类酵母形态的类群中发生了丢失。子囊菌门与担子菌门间的同源蛋白数量差异显著。系统发育分析表明，双核真菌（Dikarya）的祖先携带多份角-Platanin基因拷贝，且这些拷贝在子囊菌门与担子菌门中发生了差异化演化；同时该基因家族可能在担子菌门中发生了扩张。几乎所有同源蛋白均含有信号肽序列，成熟蛋白的长度主要集中在105至134个氨基酸残基范围内。参与形成两个二硫键的4个半胱氨酸残基以及特征序列（CSD或CSN）在绝大多数同源蛋白中均高度保守。上述结果表明，角-Platanin家族在担子菌门中的多样性高于子囊菌门。