Roles of GIG1 and UVI4 in genome duplication in Arabidopsis thaliana.
Endomitosis and endoreplication are atypical modes of cell cycle that results in genome duplication in single nucleus. Because the cell size of given cell type is generally proportional to the nuclear DNA content, endoreplication and endomitosis are effective strategy of cell growth, which are widespread in multicellular organisms, especially those in plant kingdom. We found that these processes might be differently regulated by GIGAS CELL1 (GIG1) and its paralog UV-INSENSITIVE4 (UVI4) in Arabidopsis thaliana. GIG1 and UVI4 may negatively regulate activities of anaphase-promoting complex or cyclosome (APC/C) ubiquitin ligase that acts as an important mitotic regulator. The gig1 mutation induced ectopic occurrence of endomitosis during somatic cell division, while it has been reported that uvi4 mutation resulted in premature occurrence of endoreplication during organ development. Overexpression of GIG1 and UVI4 dramatically increased the amount of mitotic cyclin, CYCB1;1, a well-known substrate of APC/C. Ectopic endomitosis in gig1 was enhanced by mutation in CYCB2;2 and suppressed by downregulation of APC10 encoding a core subunit of APC/C. Overexpression of CDC20.1, an activator protein of APC/C, further promoted the ectopic endomitosis in gig1. These findings suggest that endomitosis and endoreplication are regulated by similar molecular mechanisms, in which two related proteins, GIG1 and UVI4, may inhibit APC/C in different ways.
Graduate School of Bioagricultural Sciences; Nagoya University; Chikusa, Nagoya, Japan.
Eriko
E
Iwata
Saki
S
Ikeda
Natsumi
N
Abe
Asuka
A
Kobayashi
Mariko
M
Kurata
Sachihiro
S
Matsunaga
Yasushi
Y
Yoshioka
Marie-Claire
MC
Criqui
Pascal
P
Genschik
Masaki
M
Ito
D064173:Anaphase-Promoting Complex-Cyclosome; D017360:Arabidopsis / Q000235:genetics* / Q000378:metabolism; D029681:Arabidopsis Proteins / Q000378:metabolism; D018797:Cell Cycle Proteins / Q000235:genetics* / Q000378:metabolism; D002455:Cell Division / Q000235:genetics; D019926:Cyclin B / Q000378:metabolism; D015536:Down-Regulation; D062951:Endoreduplication; D015870:Gene Expression; D018506:Gene Expression Regulation, Plant; D017343:Genes, Plant; D018745:Genome, Plant; D008938:Mitosis / Q000235:genetics*; D009154:Mutation; D043743:Ubiquitin-Protein Ligase Complexes / Q000378:metabolism
D029681:Arabidopsis Proteins; D018797:Cell Cycle Proteins; C462528:CycB1 protein, Arabidopsis; D019926:Cyclin B; D043743:Ubiquitin-Protein Ligase Complexes; D064173:Anaphase-Promoting Complex-Cyclosome