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Both tuberization and flowering are influenced by photoperiod in potato. TERMINAL FLOWER1 is a key regulator of floral timing in Arabidopsis and other herbaceous species. In order to clarify the relationship of TFL1 protein with tuberization, a homolog of TFL1, designated Solanum tuberosumTFL1 (StTFL1; accession no. DQ307621), was isolated from potato plantlets by reverse transcriptase-PCR and rapid amplification of cDNA ends. The predicted amino acid sequence of this cDNA had a high degree of identity with other homologous members of the phosphatidylethanolamine-binding protein family. Analysis of mRNA levels for StTFL1 showed that it was highly expressed in roots and initial stolons, with the expression becoming progressively weaker during subsequent tuberization. Over-expression of StTFL1 resulted in normal tuberization in transgenic lines under the long-day condition. These results demonstrate that StTFL1 is involved in the regulation of tuberization.

A homologue of FLORICAULA/LFY, designated StLEAFY (accession number EF062357), was isolated from potato by reverse transcriptase-polymerase chain reaction (RT-PCR) and rapid amplification of cDNA ends. The complementary DNA (cDNA) sequence of StLFY was 1,417 bp long and contained an open reading frame of 1,257 bp. Its corresponding genomic sequence (EU371047) showed that the StLFY gene contained three exons and two introns. The predicted amino acid sequence of the gene consisted of 418 amino acids and had a conserved region in the C-terminal when being aligned with sequences of other LFY homologues. The StLFY protein had a high identity with LFY homologous members from other species. Analysis of StLFY expression at the mRNA level by RT-PCR showed that it was slightly expressed in the apical buds, floral buds, and initial stolons.