Shine Alaina M, Shakya Viplendra Ps, Idnurm Alexander
Division of Cell Biology and Biophysics, School of Biological Sciences, University of Missouri-Kansas City, Kansas City, MO 64110, USA.
Division of Cell Biology and Biophysics, School of Biological Sciences, University of Missouri-Kansas City, Kansas City, MO 64110, USA ; School of BioSciences, University of Melbourne, Melbourne, Vic 3010, Australia.
Fungal Biol Biotechnol. 2015 Mar 28;2. doi: 10.1186/s40694-015-0013-3.
Phytochelatin synthase (PCS) is an enzyme that catalyzes the biosynthesis of phytochelatin from glutathione. Phytochelatins protect cells against the toxic effects of non-essential heavy metals, such as cadmium, and hence growth is restricted in the presence of these metals in mutants in PCS-encoding genes. PCS genes from fungi have been characterized in only two species in the Ascomycota, and these genes are considered sparsely distributed in the fungal kingdom.
A gene encoding a putative PCS was identified in sp. strain IAM 13481, a fungus that is a member of the Pucciniomycotina subphylum of the Basidiomycota. The function of this gene was assessed by heterologous expression in the Ascomycota yeasts and , and by mutating the gene in . The gene is required for tolerance to toxic concentrations of non-essential cadmium as well as the essential metal copper. Pcs1 homologs in fungi and other eukaryotes have putative targeting sequences for mitochondrial localization: the homolog was fused to green fluorescent protein and it co-localized with a mitochondrial dye. Evaluation of the presence or absence of PCS and PCS-like homologs in the genome sequences of fungi indicates that they have a wide distribution, and the absence in most Ascomycota and Basidiomycota (the Dikarya) species can be explained by a small number of gene losses.
The ecology of the species within the fungi carrying putative PCS genes, the phenotypes of phytochelatin synthase mutants in two major fungal lineages, and the presence of homologs in many non-Dikarya lineages parallel what is seen in the plant and animal kingdoms. That is, PCS is a protein present early during the evolution of the fungi and whose role is not solely dedicated to combating toxic concentrations of non-essential metals.
植物螯合肽合酶（PCS）是一种催化从谷胱甘肽生物合成植物螯合肽的酶。植物螯合肽可保护细胞免受非必需重金属（如镉）的毒性影响，因此在编码PCS的基因突变体中，这些金属存在时生长会受到限制。真菌中的PCS基因仅在子囊菌门的两个物种中得到了表征，并且这些基因被认为在真菌界分布稀少。
在一种真菌（属于担子菌门锈菌亚门的 种菌株IAM 13481）中鉴定出一个编码假定PCS的基因。通过在子囊菌酵母 和 中进行异源表达以及在 中对该基因进行突变来评估其功能。该基因对于耐受非必需镉以及必需金属铜的毒性浓度是必需的。真菌和其他真核生物中的Pcs1同源物具有线粒体定位的假定靶向序列： 同源物与绿色荧光蛋白融合，并与线粒体染料共定位。对真菌基因组序列中PCS和PCS样同源物的存在与否进行评估表明它们分布广泛，并且大多数子囊菌门和担子菌门（双核菌亚门）物种中不存在该基因可由少数基因丢失来解释。
携带假定PCS基因的真菌物种的生态学、两个主要真菌谱系中植物螯合肽合酶突变体的表型以及许多非双核菌谱系中同源物的存在与植物和动物界的情况相似。也就是说，PCS是一种在真菌进化早期就存在的蛋白质，其作用并不 solely dedicated to combating toxic concentrations of non-essential metals（此句英文有误，无法准确翻译，推测为“其作用并非仅仅是对抗非必需金属的毒性浓度”） 。
