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flowering in strawberries has not been studied and the genetic flowering path-
ways are still poorly understood. The comparison of everbearing and short-day
genotypes of wild strawberry could facilitate our understanding of fundamen-
tal molecular mechanisms regulating perennial growth cycle in plants.
Results
We have searched homologs for 118 Arabidopsis flowering time genes from
Fragaria by EST sequencing and bioinformatics analysis and identified 66
gene homologs that by sequence similarity, putatively correspond to genes of
all known genetic flowering pathways. The expression analysis of 25 select-
ed genes representing various flowering pathways did not reveal large differ-
ences between the everbearing and the short-day genotypes. However, puta-
tive floral identity and floral integrator genes AP1 and LFY were co-regulated
during early floral development. AP1 mRNA was specifically accumulating
in the shoot apices of the everbearing genotype, indicating its usability as a
marker for floral initiation. Moreover, we showed that flowering induction in
everbearing 'Baron Solemacher' and 'Hawaii-4' was inhibited by short-day
and low temperature, in contrast to short-day genotypes.
Conclusion
We have shown that many central genetic components of the flowering path-
ways in Arabidopsis can be identified from strawberry. However, novel regula-
tory mechanisms exist, like SFL that functions as a switch between short-day/
low temperature and long-day/high temperature flowering responses between
the short-day genotype and the everbearing 'Baron Solemacher'. The identifi-
cation of putative flowering gene homologs and AP1 as potential marker gene
for floral initiation will strongly facilitate the exploration of strawberry flow-
ering pathways.
Background
Transition from vegetative to reproductive growth is one of the most important
developmental switches in plant's life cycle. In annual plants, like Arabidopsis,
flowering and consequent seed production is essential for the survival of the pop-
ulation until the following season. To assure timely flowering in various environ-
ments, Arabidopsis utilizes several genetic pathways that are activated by various
external or internal cues. Light and temperature, acting through photoperiod,
light quality, vernalization and ambient temperature pathways, are the most im-
portant environmental factors regulating flowering time [1]. Moreover, gibberel-
lin (GA) and autonomous pathways promote flowering by responding to internal
cues [2,3]. In contrast to annual plants, the growth of perennials continues after
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