PAG-XIV  Plant & Animal Genomes XIV Conference

January 14-18, 2006
Town & Country Convention Center
San Diego, CA


Workshop: Maize

W55

Gene Expression And Phylogenetic Relationships Reveal A Complex Protein Disulfide Isomerase Family

Rudolf Jung1 , Norma L. Houston2 , Jenny Q. Xiang2 , Rebecca S. Boston2

1  Pioneer Hi-Bred International, Inc., A DuPont Company,7300 NW 62nd Ave.,Johnston, IA, 50131, USA
2  NC State University, Plant Biology and Genetics, Campus Box 7612, Raleigh, NC, 27695, USA

Protein disulfide isomerases (PDIs) catalyze the formation of proper disulfide bonds and participate in ER quality control as part of the cellular ER-stress response. To identify plant PDI-like (PDIL) proteins, we performed a genome-wide search of Arabidopsis thaliana and identified 104 thioredoxin (TRX) domain containing proteins, 22 of which group with orthologs of known plant PDIs in a well-supported clade. Using the Arabidopsis PDIL sequences in iterative BLAST searches, we identified orthologous sets of plant PDIL sequences in rice (19) and maize (22). Comparison of these three plant species representing the two major evolutionary groups in plants provided an explicit view of the sequential evolutionary events that resulted in the diversity observed for this protein family. The phylogenetic analysis resolved the phylogeny into 10 classes. Five classes (I-V) had the two TRX domains typically found in PDIL proteins in other higher eukaryotes while the remaining five classes (VI-X) had a single TRX domain. RNA profiling and quantitative RT-PCR analyses of the maize PDILs (ZmPDILs) showed marked differences in expression within and among classes. The major PDI (ZmPDIL1-1), the class V PDIL (ZmPDIL2-3), and the class VI maize PDIL (ZmPDIL5-1) were up-regulated by ER stress. In contrast to other members of the PDI protein family, the single domain ZmPDIL5-1 was not localized to the intracellular membrane fractions suggestive of an unusual role . This study provides a model for effective use of high throughput and genomic sequencing information as a foundation for experiment based analysis that leads to complete, accurate and permanently useful datasets.