Analysis of coniferFLOWERING LOCUS T/TERMINAL FLOWER1‐like genes provides evidence for dramatic biochemical evolution in the angiospermFTlineage

Abstract

SummaryIn flowering plants, homologs of the Arabidopsis phosphatidylethanolamine-binding protein (PEBP) FLOWERING LOCUS T (FT) are key components in controlling flowering time. We show here that, although FT homologs are found in all angiosperms with completed genome sequences, there is no evidence to date that FT-like genes exist in other groups of plants.Through phylogeny reconstructions and heterologous expression, we examined the biochemical function of the Picea (spruces) and Pinus (pines) PEBP families -two gymnosperm taxa phylogenetically distant from the angiosperms.We have defined a lineage of gymnosperm PEBP genes, termed the FT/TERMINAL FLOWER1 (TFL1)-like genes, that share sequence characteristics with both the angiosperm FT-and TFL1-like clades. When expressed in Arabidopsis, FT/TFL1-like genes repressed flowering, indicating that the proteins are biochemically more similar to the angiosperm TFL1-like proteins than to the FT-like proteins. This suggests that the regulation of the vegetative-to-reproductive switch might differ in gymnosperms compared with angiosperms.Molecular evolution studies suggest that plasticity at exon 4 contributes to the divergence of FT-like function in floral promotion. In addition, the presence of FT-like genes in basal angiosperms indicates that the FT-like function emerged at an early stage during the evolution of flowering plants as a means to regulate flowering time.

FLOWERING LOCUS T/TERMINAL FLOWER1-Like Genes Affect Growth Rhythm and Bud Set in Norway Spruce

“…Three independent experiments with approximately 40 bombardments each were performed, but all of them failed to produce viable callus. Similar results were also reported by Klintenas et al (2012). Since it appeared impossible to produce viable transgenic Norway spruce lines constitutively expressing PaFTL2, we instead tested to activate PaFTL2 from an inducible heat shock promoter (hsp::PaFTL2).…”

“…When PaFTL1 and PaFTL2 were ectopically expressed in Arabidopsis, flowering time was delayed and flower morphology showed similarities with TFL1 overexpressors (Karlgren et al, 2011;Klintenas et al, 2012). Expressing PaFTL1 and PaFTL2 in the tfl1 mutant further showed that both genes can substitute for TFL1 (Klintenas et al, 2012). These data suggest that the flowering-promoting function of FT evolved after the split between angiosperms and gymnosperms (Karlgren et al, 2011).…”

“…Whether these newly identified genes are expressed and functional is, to our knowledge, unknown at present. When PaFTL1 and PaFTL2 were ectopically expressed in Arabidopsis, flowering time was delayed and flower morphology showed similarities with TFL1 overexpressors (Karlgren et al, 2011;Klintenas et al, 2012). Expressing PaFTL1 and PaFTL2 in the tfl1 mutant further showed that both genes can substitute for TFL1 (Klintenas et al, 2012).…”

The Norway spruce genome sequence and conifer genome evolution

“…It has been suggested that gymnosperms lack orthologues of FT genes, instead containing a group of FT/TFL1-like genes that probably act as flowering repressors 36,37 . We identified four putative FT/TFL1-like genes in the P.abies 1.0 genome that have not been previously described and confirmed that the genome does indeed lack FT-like genes (Supplementary Information 5.1).…”

Polyploidy-associated genome modifications during land plant evolution

“…R. Soc. B 369: 20130355 abies, lacks flowering locus T (FT)-like genes (that promote flowering in other taxa), instead containing a group of FT/TFL1-like genes which probably act as flowering repressors [28,46,47]. The FT-like genes are exclusively found in angiosperms, including early diverging and eudicot lineages, supporting the hypothesis that the evolution of flowering plants coincided with the evolution of a flower-promoting function for an FT/TFL1-like gene.…”