Ondzighi-Assoume, Christine Andeme , Christopher, David A. , Cho, Eun-Ju , Shoeng-Chang, Shu , Staehelin, L. Andrew .
During Biogenesis of Nucellus Cells in Developing Seeds, Arabidopsis Protein Disulfide Isomerase 5 Traffics Together with Cysteine Proteases to Protein Storage and Lytic Vacuoles.
Protein Disulfide Isomerase (PDI) catalyzes the formation, reduction and isomerization of disulfide bonds of proteins in the ER of eukaryotic cells. PDI also serves as a redox-response regulator and a protein-folding chaperone. The Arabidopsis genome contains 12 PDI genes suggesting a diversity of functions for this gene family. We report here on the isolation and characterization of AtPDI5. The deduced AtPDI5 protein has 501 amino acids, two putative thioredoxin catalytic domains (PWCghC), and an ER-retention (KDEL) motif. The Atpdi5 gene identified on Arabidopsis chromosome1 contains a specific T-DNA SALK insertion in the 5'UTR. A polyclonal antiserum generated against a unique peptide within AtPDI5 binds specifically to a 68 KDa protein expressed in wild type plants, which is lacking in the Atpdi5-knockout line. The Atpdi5Δ mutant has more flower trichomes, aborted ovules in the siliques, and accumulated callose in embryos and flowers. Immunolabeling experiments show that AtPDI5 is expressed in flower tissues and in nucellus cells of developing seeds. AtPDI5 localizes to the ER and accumulates in the protein storage (PSV) and lytic (LV) vacuoles of nucellus cells. Co-localization with anti-δ-TIP (Tonoplast Intrinsic Protein) antibodies demonstrates that AtPDI5 is more concentrated in PSVs. In the yeast two-hybrid analysis, AtPDI5 interacts with three different Arabidopsis cysteine proteases, one of which, RD21 co-localizes together with AtPDI5 in both PSVs and LVs. Expression of AtPDI5 correlates with Programmed Cell Death (PCD) of the nucellus. We propose that AtPDI5 plays a critical role in chaperoning, sorting and trafficking of cysteine proteases produced during PCD of nucellus cells in developing seeds. Supported by grant NFS # MCB03-48028 to DAC and LAS.
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1 - University of Colorado, MCD Biology, UCB 347, Boulder, Colorado, 80309-0347, USA
2 - University of Hawaii, MBBE
3 - University of Colorado, MCD Biology, UCB 347
Presentation Type: ASPB Minisymposium
Location: Continental C/Hilton
Date: Sunday, July 8th, 2007
Time: 5:00 PM