Structure and expression of OsUBP6, an ubiquitin-specific protease 6 homolog in rice (Oryza sativa L.).
Although the possible cellular roles of several ubiquitin-specific proteases (UBPs) were identified in Arabidopsis, almost nothing is known about UBP homologs in rice, a monocot model plant. In this report, we searched the rice genome database ( http://signal.salk.edu/cgi-bin/RiceGE ) and identified 21 putative UBP family members (OsUBPs) in the rice genome. These OsUBP genes each contain a ubiquitin carboxyl-terminal hydrolase (UCH) domain with highly conserved Cys and His boxes and were subdivided into 9 groups based on their sequence identities and domain structures. RT-PCR analysis indicated that rice OsUBP genes are expressed at varying degrees in different rice tissues. We isolated a full-length cDNA clone for OsUBP6, which possesses not only a UCH domain, but also an N-terminal ubiquitin motif. Bacterially expressed OsUBP6 was capable of dismantling K48-linked tetraubiquitin chains in vitro. Quantitative real-time RT-PCR indicated that OsUBP6 is constitutively expressed in different tissues of rice plants. An in vivo targeting experiment showed that OsUBP6 is predominantly localized to the nucleus in onion epidermal cells. We also examined how knock-out of OsUBP6 affects developmental growth of rice plants. Although homozygous T3 osubp6 T-DNA insertion mutant seedlings displayed slower growth relative to wild type seedlings, mature mutant plants appeared to be normal. These results raise the possibility that loss of OsUBP6 is functionally compensated for by an as-yet unknown OsUBP homolog during later stages of development in rice plants.
Department of Biology, College of Life Science and Biotechnology, Yonsei University, Seoul 120-749, Korea.
Yea Kyung
YK
Moon
Jong-Pil
JP
Hong
Young-Chan
YC
Cho
Sae-Jun
SJ
Yang
Gynheung
G
An
Woo Taek
WT
Kim
D000595:Amino Acid Sequence; D004269:DNA, Bacterial / Q000235:genetics; D018076:DNA, Complementary / Q000235:genetics / Q000302:isolation & purification; D010450:Endopeptidases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D020869:Gene Expression Profiling; D018507:Gene Expression Regulation, Developmental; D018506:Gene Expression Regulation, Plant; D017343:Genes, Plant / Q000235:genetics; D008969:Molecular Sequence Data; D016254:Mutagenesis, Insertional / Q000235:genetics; D019697:Onions / Q000166:cytology; D009928:Organ Specificity / Q000235:genetics; D012275:Oryza / Q000201:enzymology* / Q000235:genetics; D010940:Plant Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D017434:Protein Structure, Tertiary; D021381:Protein Transport; D020133:Reverse Transcriptase Polymerase Chain Reaction; D020539:Sequence Analysis, Protein; D017386:Sequence Homology, Amino Acid; D013312:Stress, Physiological / Q000235:genetics; D013347:Subcellular Fractions / Q000378:metabolism; D064570:Ubiquitin-Specific Proteases; D054875:Ubiquitination
D004269:DNA, Bacterial; D018076:DNA, Complementary; D010940:Plant Proteins; C036483:T-DNA; D010450:Endopeptidases; D064570:Ubiquitin-Specific Proteases