The E3 ubiquitin ligase BIG BROTHER controls arabidopsis organ size in a dosage-dependent manner.
Organ growth up to a species-specific size is tightly regulated in plants and animals. Final organ size is remarkably constant within a given species, suggesting that a species-specific size checkpoint terminates organ growth in a coordinated and timely manner. Phytohormones influence plant organ size, but their precise functions in size control are unclear because of their pleiotropic and complex developmental roles. The Arabidopsis transcription factors AINTEGUMENTA and JAGGED promote organ growth by maintaining cellular proliferation potential. Loss of the Antirrhinum transcription factor CINCINNATA causes leaf overgrowth, yet also leads to a highly abnormal leaf shape. Thus, no dedicated factor that limits the final size of plant organs has been isolated. Here, we identify the novel RING-finger protein BIG BROTHER (BB) as a repressor of plant organ growth. Small changes in BB expression levels substantially alter organ size, indicating a central regulatory role for BB in growth control. Recombinant BB protein has E3 ubiquitin-ligase activity that is essential for its in vivo function, suggesting that BB acts by marking cellular proteins for degradation. Our data indicate that plants limit the duration of organ growth and ultimately organ size by actively degrading critical growth stimulators.
Disch
Sabine
S
Institut für Biologie III, Universität Freiburg, Schänzlestrasse 1, D-79104 Freiburg, Germany.
Anastasiou
Elena
E
Sharma
Vijay K
VK
Laux
Thomas
T
Fletcher
Jennifer C
JC
Lenhard
Michael
M
D000595:Amino Acid Sequence; D017360:Arabidopsis; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D001483:Base Sequence; D018797:Cell Cycle Proteins / Q000378:metabolism; D018628:Gene Dosage / Q000235:genetics; D018506:Gene Expression Regulation, Plant; D017403:In Situ Hybridization; D008969:Molecular Sequence Data; D009154:Mutation / Q000235:genetics; D009929:Organ Size / Q000235:genetics; D010641:Phenotype; D035261:Plant Components, Aerial / Q000254:growth & development*; D011994:Recombinant Proteins / Q000378:metabolism; D017422:Sequence Analysis, DNA; D014157:Transcription Factors / Q000378:metabolism; D044767:Ubiquitin-Protein Ligases / Q000235:genetics / Q000378:metabolism*
C099055:AINTEGUMENTA protein, Arabidopsis; D029681:Arabidopsis Proteins; D018797:Cell Cycle Proteins; C484013:JAGGED protein, Arabidopsis; D011994:Recombinant Proteins; D014157:Transcription Factors; C515186:BIG BROTHER protein, Arabidopsis; D044767:Ubiquitin-Protein Ligases