Analysis of the Arabidopsis MADS AFFECTING FLOWERING gene family: MAF2 prevents vernalization by short periods of cold.
The Arabidopsis FLOWERING LOCUS C (FLC) gene is a key floral repressor in the maintenance of a vernalization response. In vernalization-sensitive genetic backgrounds, FLC levels are high, and they decline after exposure to long cold periods. Four FLC paralogs (MAF2 [MADS AFFECTING FLOWERING2] to MAF5) are arranged in a tandem array on the bottom of Arabidopsis chromosome V. We used a reverse genetics approach to analyze their functions. Loss-of-function and gain-of-function studies indicate that MAF2 acts as a floral repressor. In particular, maf2 mutant plants display a pronounced vernalization response when subjected to relatively short cold periods, which are insufficient to elicit a strong flowering response in the wild type, despite producing a large reduction in FLC levels. MAF2 expression is less sensitive to vernalization than that of FLC, and its repressor activity is exerted independently or downstream of FLC transcription. Thus, MAF2 can prevent premature vernalization in response to brief cold spells. Overexpression of MAF3 or MAF4 produces alterations in flowering time that suggest that these genes also act as floral repressors and might contribute to the maintenance of a vernalization requirement. However, the final gene in the cluster, MAF5, is upregulated by vernalization. Therefore, MAF5 could play an opposite role to FLC in the vernalization response.
Ratcliffe
Oliver J
OJ
Mendel Biotechnology, Inc., Hayward, California 94545, USA. oratclif@mendelbio.com
Kumimoto
Roderick W
RW
Wong
Becky J
BJ
Riechmann
José Luis
JL
D000064:Acclimatization / Q000235:genetics / Q000502:physiology; D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism; D029681:Arabidopsis Proteins / Q000235:genetics* / Q000378:metabolism; D003080:Cold Temperature; D004269:DNA, Bacterial / Q000235:genetics; D018076:DNA, Complementary / Q000737:chemistry / Q000235:genetics; D035264:Flowers / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism; D018507:Gene Expression Regulation, Developmental; D018506:Gene Expression Regulation, Plant; D026161:MADS Domain Proteins / Q000235:genetics* / Q000378:metabolism; D008969:Molecular Sequence Data; D016254:Mutagenesis, Insertional; D009154:Mutation; D010641:Phenotype; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid; D013997:Time Factors
C419046:AGL20 protein, Arabidopsis; D029681:Arabidopsis Proteins; D004269:DNA, Bacterial; D018076:DNA, Complementary; C418902:At5g10140 protein, Arabidopsis; D026161:MADS Domain Proteins; C036483:T-DNA