title: Phylogenetic characterization and promoter expression analysis of a novel hybrid protein disulfide isomerase/cargo receptor subfamily unique to plants and chromalveolates.
abstract: Protein disulfide isomerases (PDIs) play critical roles in protein folding by catalyzing the formation and rearrangement of disulfide bonds in nascent secretory proteins. There are six distinct PDI subfamilies in terrestrial plants. A unique feature of PDI-C subfamily members is their homology to the yeast retrograde (Golgi-to-endoplasmic reticulum) cargo receptor proteins, Erv41p and Erv46p. Here, we demonstrate that plant Erv41p/Erv46p-like proteins are divided into three subfamilies: ERV-A, ERV-B and PDI-C, which all possess the N-proximal and C-proximal conserved domains of yeast Erv41p and Erv46p. However, in PDI-C isoforms, these domains are separated by a thioredoxin domain. The distribution of PDI-C isoforms among eukaryotes indicates that the PDI-C subfamily likely arose through an ancient exon-shuffling event that occurred before the divergence of plants from stramenopiles and rhizarians. Arabidopsis has three PDI-C genes: PDI7, PDI12, and PDI13. PDI12- and PDI13-promoter: β-glucuronidase (GUS) gene fusions are co-expressed in pollen and stipules, while PDI7 is distinctly expressed in the style, hydathodes, and leaf vasculature. The PDI-C thioredoxin domain active site motif CxxS is evolutionarily conserved among land plants. Whereas PDI12 and PDI13 retain the CxxS motif, PDI7 has a CxxC motif similar to classical PDIs. We hypothesize that PDI12 and PDI13 maintain the ancestral roles of PDI-C in Arabidopsis, while PDI7 has undergone neofunctionalization. The unusual PDI/cargo receptor hybrid arrangement in PDI-C isoforms has no counterpart in animals or yeast, and predicts the need for pairing redox functions with cargo receptor processes during protein trafficking in plants and other PDI-C containing organisms.
authors: Department of Molecular Biosciences and Bioengineering, University of Hawaii, 1955 East-West Rd., Ag. Science Rm 218, Honolulu, HI, 96822, USA.
authors: Christen Y L
authors: CY
authors: Yuen
authors: Department of Molecular Biosciences and Bioengineering, University of Hawaii, 1955 East-West Rd., Ag. Science Rm 218, Honolulu, HI, 96822, USA.
authors: Katharine
authors: K
authors: Wong
authors: Department of Molecular Biosciences and Bioengineering, University of Hawaii, 1955 East-West Rd., Ag. Science Rm 218, Honolulu, HI, 96822, USA. dchr@hawaii.edu.
authors: David A
authors: DA
authors: Christopher
mesh_terms: D000818:Animals; D017360:Arabidopsis / Q000235:genetics*; D020134:Catalytic Domain / Q000235:genetics; D004721:Endoplasmic Reticulum / Q000235:genetics; D005091:Exons / Q000235:genetics; D005966:Glucuronidase / Q000235:genetics; D006056:Golgi Apparatus / Q000235:genetics; D010802:Phylogeny; D011401:Promoter Regions, Genetic / Q000235:genetics*; D019704:Protein Disulfide-Isomerases / Q000235:genetics*; D017510:Protein Folding; D017434:Protein Structure, Tertiary; D013879:Thioredoxins / Q000235:genetics; D015003:Yeasts / Q000235:genetics
chemical_list: D013879:Thioredoxins; D005966:Glucuronidase; D019704:Protein Disulfide-Isomerases
keywords: Cargo receptor; Endoplasmic reticulum; Golgi apparatus; Protein disulfide isomerase