Gibberellin regulates Arabidopsis seed germination via RGL2, a GAI/RGA-like gene whose expression is up-regulated following imbibition.
The germination of Arabidopsis seeds is promoted by gibberellin (GA). Arabidopsis GAI, and RGA are genes encoding key GA signal-transduction components (GAI and RGA) that mediate GA regulation of stem elongation. The Arabidopsis genome contains two further genes, RGL1 and RGL2, that encode proteins (RGL1 and RGL2) that are closely related to GAI and RGA. Here, we show that RGL2 regulates seed germination in response to GA, and that RGL1, GAI, and RGA do not. In addition, we show that RGL2 transcript levels rise rapidly following seed imbibition, and then decline rapidly as germination proceeds. In situ GUS staining revealed that RGL2 expression in imbibed seeds is restricted to elongating regions of pre-emergent and recently emerged radicles. These observations indicate that RGL2 is a negative regulator of GA responses that acts specifically to control seed germination rather than stem elongation. Furthermore, as RGL2 expression is imbibition inducible, RGL2 may function as an integrator of environmental and endogenous cues to control seed germination.
Lee
Sorcheng
S
Institute of Molecular Agrobiology, National University of Singapore, Singapore 117604.
Cheng
Hui
H
King
Kathryn E
KE
Wang
Weefuen
W
He
Yawen
Y
Hussain
Alamgir
A
Lo
Jane
J
Harberd
Nicholas P
NP
Peng
Jinrong
J
D000595:Amino Acid Sequence; D017360:Arabidopsis; D029681:Arabidopsis Proteins / Q000235:genetics*; D017124:Conserved Sequence; D018506:Gene Expression Regulation, Plant; D018525:Germination / Q000502:physiology*; D005875:Gibberellins / Q000494:pharmacology*; D008969:Molecular Sequence Data; D009154:Mutation; D018515:Plant Leaves / Q000254:growth & development; D010940:Plant Proteins / Q000235:genetics; D018547:Plant Stems / Q000254:growth & development; D012639:Seeds / Q000502:physiology; D017386:Sequence Homology, Amino Acid; D015398:Signal Transduction; D013489:Suppression, Genetic; D014157:Transcription Factors / Q000235:genetics; D014230:Triazoles / Q000494:pharmacology; D015854:Up-Regulation; D014867:Water / Q000378:metabolism
D029681:Arabidopsis Proteins; C109555:GAI protein, Arabidopsis; D005875:Gibberellins; D010940:Plant Proteins; C450824:RGL1 protein, Arabidopsis; C450823:RGL2 protein, Arabidopsis; D014157:Transcription Factors; D014230:Triazoles; D014867:Water; C053370:paclobutrazol