Activation of CRABS CLAW in the Nectaries and Carpels of Arabidopsis.
CRABS CLAW (CRC), a member of the YABBY gene family, is required for nectary and carpel development. To further understand CRC regulation in Arabidopsis thaliana, we performed phylogenetic footprinting analyses of 5' upstream regions of CRC orthologs from three Brassicaceae species, including Arabidopsis. Phylogenetic footprinting efficiently identified functionally important regulatory regions (modules), indicating that CRC expression is regulated by a combination of positive and negative regulatory elements in the modules. Within the conserved modules, we identified putative binding sites of LEAFY and MADS box proteins, and functional in vivo analyses revealed their importance for CRC expression. Both expression and genetic studies demonstrate that potential binding sites for MADS box proteins within the conserved regions are functionally significant for the transcriptional regulation of CRC in nectaries. We propose that in wild-type flowers, a combination of floral homeotic gene activities, specifically the B class genes APETALA3 and PISTILLATA and the C class gene AGAMOUS act redundantly with each other and in combination with SEPALLATA genes to activate CRC in the nectaries and carpels. In the absence of B and C class gene activities, other genes such as SHATTERPROOF1/2 can substitute if they are ectopically expressed, as in an A class mutant background (apetala2). These MADS box proteins may provide general floral factors that must work in conjunction with specific factors in the activation of CRC in the nectaries and carpels.
Lee
Ji-Young
JY
Section of Plant Biology, University of California Davis, Davis, California 95616, USA.
Baum
Stuart F
SF
Alvarez
John
J
Patel
Amita
A
Chitwood
Daniel H
DH
Bowman
John L
JL
D026342:AGAMOUS Protein, Arabidopsis / Q000235:genetics; D017360:Arabidopsis / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism; D029681:Arabidopsis Proteins / Q000235:genetics* / Q000378:metabolism; D001665:Binding Sites / Q000235:genetics; D001937:Brassica / Q000235:genetics / Q000254:growth & development / Q000378:metabolism; D017124:Conserved Sequence / Q000235:genetics; D018983:DNA Footprinting; D019143:Evolution, Molecular; D035264:Flowers / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism; D018506:Gene Expression Regulation, Plant / Q000235:genetics*; D005801:Genes, Homeobox / Q000235:genetics; D017343:Genes, Plant / Q000235:genetics*; D005809:Genes, Regulator / Q000235:genetics; D029686:Lepidium / Q000235:genetics / Q000254:growth & development / Q000378:metabolism; D026161:MADS Domain Proteins / Q000235:genetics; D009154:Mutation / Q000235:genetics; D010802:Phylogeny; D011401:Promoter Regions, Genetic / Q000235:genetics; D013045:Species Specificity; D014157:Transcription Factors / Q000235:genetics* / Q000378:metabolism; D015533:Transcriptional Activation / Q000235:genetics
D026342:AGAMOUS Protein, Arabidopsis; C101342:APETALA 3 protein, Arabidopsis; D029681:Arabidopsis Proteins; C119755:CRC protein, Arabidopsis; D026161:MADS Domain Proteins; C090225:PISTILLATA protein, Arabidopsis; C419044:SHP1 protein, Arabidopsis; D014157:Transcription Factors