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GENETICS, GENOMICS, AND MOLECULAR EVOLUTION

FRIGIDA LIKE 2 Is a Functional Allele in Landsberg erecta and Compensates for a Nonsense Allele of FRIGIDA LIKE 1^1,[W],[OA]

Department of Biological Sciences, Marquette University, Milwaukee, Wisconsin 53233

The Landsberg erecta (Ler) accession of Arabidopsis (Arabidopsis thaliana) has a weak allele of the floral inhibitor FLOWERING LOCUS C (FLC). FLC-Ler is weakly up-regulated by the active San Feliu-2 (Sf2) allele of FRIGIDA (FRI-Sf2), resulting in a moderately late-flowering phenotype. By contrast, the Columbia (Col) allele of FLC is strongly up-regulated by FRI-Sf2, resulting in a very late-flowering phenotype. In Col, the FRI-related gene FRI LIKE 1 (FRL1) is required for FRI-mediated up-regulation of FLC. It is shown here that in Ler, the FRL1-related gene FRI LIKE 2 (FRL2), but not FRL1, is required for FRI-mediated up-regulation of FLC. FRL1-Ler is shown to be a nonsense allele of FRL1 due to a naturally occurring premature stop codon in the middle of the conceptual protein sequence, suggesting that FRL1-Ler is nonfunctional. Compared to FRL2-Col, FRL2-Ler has two amino acid changes in the conceptual protein sequence. Plants homozygous for FRI-Sf2, FLC-Ler, FRL1-Ler, and FRL2-Col have no detectable FLC expression, resulting in an extremely early flowering phenotype. Transformation of a genomic fragment of FRL2-Ler, but not of FRL2-Col, into a recombinant inbred line derived from these plants restores both FRI-mediated up-regulation of FLC expression and a late-flowering phenotype, indicating that FRL2-Ler is the functional allele of FRL2. Taken together, these results suggest that in the two different Arabidopsis accessions Col and Ler, either FRL1 or FRL2, but not both, is functional and required for FRI-mediated up-regulation of FLC.

The author responsible for distribution of materials integral to the findings presented in this article in accordance with the policy described in the Instructions for Authors (www.plantphysiol.org) is: Michael R. Schläppi (michael.schlappi{at}marquette.edu).

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www.plantphysiol.org/cgi/doi/10.1104/pp.106.085571

^* E-mail michael.schlappi{at}marquette.edu; fax 414–288–1480.

Received June 30, 2006; accepted October 12, 2006; published October 20, 2006.

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