Aberrant expression of the light-inducible and circadian-regulated APRR9 gene belonging to the circadian-associated APRR1/TOC1 quintet results in the phenotype of early flowering in Arabidopsis thaliana.
Several Arabidopsis genes have been proposed to encode potential clock-associated components, including the Myb-related CCA1 and LHY transcription factors and a member (APRR1/TOC1) of the family of pseudo-response regulators. We previously showed that transcripts of the APRR1/TOC1 family genes each start accumulating after dawn rhythmically and sequentially at intervals in the order of APRR9-->APRR7-->APRR5-->APRR3-->APRR1/TOC1, under the conditions of continuous light. Nevertheless, no evidence has been provided that each member of the APRR1/TOC1 quintet, except for APRR1/TOC1, is indeed relevant to the mechanisms underlying circadian rhythms. Here we attempt to provide such evidence by characterizing transgenic plants that aberrantly (or constitutively) express the APRR9 gene in a manner independent of circadian rhythms. The resulting APRR9-ox plants showed intriguing phenotypes with regard to circadian rhythms, in two aspects. First, the aberrant expression of APRR9 resulted in a characteristic phenotype with regard to transcriptional events, in which short-period rhythms were commonly observed for certain circadian-regulated genes, including CCA1, LHY, APRR1/TOC1, other APRR1/TOC1 members, ELF3, and CAB2. With regard to biological consequences, such APRR9-ox plants flowered much earlier than wild-type plants, in a manner independent of photoperiodicity (or under short-day conditions). These results suggest that APRR9 (and perhaps other members of the APRR1/TOC1 quintet) must also be taken into consideration for a better understanding of the molecular mechanisms underlying circadian rhythms, and also underlying control of the flowering time through the photoperiodic long-day pathway.
Matsushika
Akinori
A
Laboratory of Molecular Microbiology, School of Agriculture, Nagoya University, Chikusa-ku, Nagoya, 464-8601 Japan.
Imamura
Aya
A
Yamashino
Takafumi
T
Mizuno
Takeshi
T
D017360:Arabidopsis / Q000235:genetics* / Q000502:physiology / Q000528:radiation effects; D029681:Arabidopsis Proteins / Q000235:genetics*; D002352:Carrier Proteins / Q000502:physiology; D002940:Circadian Rhythm / Q000502:physiology*; D018506:Gene Expression Regulation, Plant / Q000528:radiation effects; D008027:Light; D045342:Light-Harvesting Protein Complexes; D005810:Multigene Family / Q000235:genetics; D010641:Phenotype; D017440:Photoperiod; D018547:Plant Stems / Q000235:genetics* / Q000502:physiology / Q000528:radiation effects; D030821:Plants, Genetically Modified; D013997:Time Factors; D014157:Transcription Factors
C091601:ABI3 protein, Arabidopsis; C448162:APRR3 protein, Arabidopsis; C448160:APRR5 protein, Arabidopsis; C448161:APRR7 protein, Arabidopsis; C448159:APRR9 protein, Arabidopsis; D029681:Arabidopsis Proteins; C423618:CAB2 protein, Arabidopsis; D002352:Carrier Proteins; D045342:Light-Harvesting Protein Complexes; C411822:TOC1 protein, Arabidopsis; D014157:Transcription Factors