B2 flowering time locus of beet encodes a zinc finger transcription factor

Sugar beet (Beta vulgaris) is a biennial root crop that grows vegetatively in the first year and starts shoot elongation (bolting) and flowering after exposure to cold temperatures over winter. Early bolting before winter is controlled by the dominant allele of the B locus. Recently, the BOLTING TIM...

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Bibliographic Details
Published in:Proceedings of the National Academy of Sciences - PNAS 2014-07, Vol.111 (28), p.10365-10370
Main Authors: Dally, Nadine, Xiao, Ke, Holtgräwe, Daniela, Jung, Christian
Format: Article
Language:English
Subjects:
Alleles
Annuals
Arabidopsis - genetics
Arabidopsis - metabolism
Arabidopsis thaliana
Beets
Beta vulgaris
Beta vulgaris - genetics
Beta vulgaris - metabolism
Biennials
Biological Sciences
Flowering
Flowers & plants
Genetic loci
Genetic Loci - physiology
Genetic mutation
Mutation
Phylogenetics
Phylogeny
Plant Proteins - genetics
Plant Proteins - metabolism
Plants
Proteins
Sugar beets
Transcription Factors - genetics
Transcription Factors - metabolism
Vernalization
Zinc Fingers - genetics
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Summary:Sugar beet (Beta vulgaris) is a biennial root crop that grows vegetatively in the first year and starts shoot elongation (bolting) and flowering after exposure to cold temperatures over winter. Early bolting before winter is controlled by the dominant allele of the B locus. Recently, the BOLTING TIME CONTROL 1 (BTC1) gene has been cloned from this locus. BTC1 promotes early bolting through repression of the downstream bolting repressor B. vulgaris FLOWERING LOCUS T1 (BvFT1) and activation of the downstream floral activator BvFT2 . We have identified a new bolting locus B2 acting epistatically to B . B2 houses a transcription factor which is diurnally regulated and acts like BTC1 upstream of BvFT1 and BvFT2 . It was termed BvBBX19 according to its closest homolog from Arabidopsis thaliana . The encoded protein has two conserved domains with homology to zinc finger B-boxes. Ethyl methanesulfonate-induced mutations within the second B-box caused up-regulation of BvFT1 and complete down-regulation of BvFT2 . In Arabidopsis , the expression of FT is promoted by the B-box containing protein CONSTANS (CO). We performed a phylogenetic analysis with B-box genes from beet and A. thaliana but only BvCOL1 clustered with CO . However, BvCOL1 had been excluded as a CO ortholog by previous studies. Therefore, a new model for flowering induction in beet is proposed in which BTC1 and BvBBX19 complement each other and thus acquire a CO function to regulate their downstream targets BvFT1 and BvFT2 .
ISSN:0027-8424
1091-6490
DOI:10.1073/pnas.1404829111