Cloning and functional assessment of the protein disulfide isomerase (PDI-V) gene and its promoter sequences from Haynaldia villosa

Abstract

Protein disulfide isomerase (PDI) and PDI-like genes encode key foldase enzymes that play an important role in disulfidebond formation, isomerization, and many other metabolic functions in plants. Our previous results indicate that the PDI-V expressionis tissue-specific and that it is upregulated by powdery mildew and other abiotic stress treatments. In the current study, the completePDI-V gene and its promoter sequence were cloned to identify gene structure and the important cis-regulating motifs responsible forvarious genes’ activities. Sequence analysis revealed the size of the cloned genomic sequence and promoter region as 5728 bp and 2086bp, respectively. The PDI-V gene had nine exons and eight introns; this showed a highly conserved gene structure with that of wheatTaPDIL-5 in terms of exon size and number of exons/introns. The phylogenetic analysis of PDI-V with orthologue sequences from theA, B, and D genome of wheat, barley, and rice clearly demonstrated that the gene was highly conserved across the grass family. In silicoanalysis of the PDI-V promoter revealed a large number of elements responsible for endosperm or embryo specific expression, and fordefense or stress responses against pathogens including fungi and other abiotic stresses such as high or low temperature and drought.Transient expression of the GUS gene in wheat leaf epidermal cells under the control of PDI-V promoter proved its functionality.However, no significant variation was observed in the number of epidermal cells having GUS activity between powdery mildewinoculated and noninoculated wheat leaves, which suggests that the 5′-untranslated region may also play a critical role in promoteractivity. This point requires further exploration.