title: Regulation of leaf organ size by the Arabidopsis RPT2a 19S proteasome subunit.
abstract: The ubiquitin/26S proteasome pathway plays a central role in the degradation of short-lived regulatory proteins, to control many cellular events. To further understand this pathway, we focused on the RPT2 subunit of the 26S proteasome regulatory particle. The Arabidopsis genome contains two genes, AtRPT2a and AtRPT2b, which encode paralog molecules of the RPT2 subunit, with a difference of only three amino acids in the protein sequences. Both genes showed similar mRNA accumulation patterns. However, the rpt2a mutant showed a specific phenotype of enlarged leaves caused by increased cell size, in correlation with increased ploidy. Detailed analyses revealed that cell expansion is increased in the rpt2a mutant by extended endoreduplication early in leaf development. The transcription of genes encoding cell cycle-related components, for DNA replication licensing and the G2/M phase, was also promoted in the rpt2a mutant, suggesting that extended endoreduplication was caused by increased DNA replication, and disrupted regulation of the G2/M checkpoint, at the proliferation stage of leaf development.
authors.affiliation: Faculty of Advanced Life Science, Hokkaido University, Kita-ku N10-W8, Sapporo 060-0810, Japan.
authors.forename: Yutaka
authors.initials: Y
authors.lastname: Sonoda
authors.forename: Kaori
authors.initials: K
authors.lastname: Sako
authors.forename: Yuko
authors.initials: Y
authors.lastname: Maki
authors.forename: Naoko
authors.initials: N
authors.lastname: Yamazaki
authors.forename: Hiroko
authors.initials: H
authors.lastname: Yamamoto
authors.forename: Akira
authors.initials: A
authors.lastname: Ikeda
authors.forename: Junji
authors.initials: J
authors.lastname: Yamaguchi
mesh_terms: D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000235:genetics* / Q000254:growth & development; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D048429:Cell Size; D004261:DNA Replication; D020440:Gene Duplication; D018507:Gene Expression Regulation, Developmental; D018506:Gene Expression Regulation, Plant; D055786:Gene Knockout Techniques; D005816:Genetic Complementation Test; D008969:Molecular Sequence Data; D016296:Mutagenesis; D018515:Plant Leaves / Q000235:genetics / Q000254:growth & development*; D011003:Ploidies; D046988:Proteasome Endopeptidase Complex / Q000235:genetics / Q000378:metabolism*; D018749:RNA, Plant / Q000378:metabolism; D016415:Sequence Alignment; D014158:Transcription, Genetic
chemical_list: D029681:Arabidopsis Proteins; D018749:RNA, Plant; C487429:RPT2a protein, Arabidopsis; D046988:Proteasome Endopeptidase Complex; C061553:ATP dependent 26S protease