CO/FT Regulatory Module Controls Timing of Flowering and Seasonal Growth Cessation in Trees

Abstract

Forest trees display a perennial growth behavior characterized by a multiple-year delay in flowering and, in temperate regions, an annual cycling between growth and dormancy. We show here that the CO/FT regulatory module, which controls flowering time in response to variations in daylength in annual plants, controls flowering in aspen trees. Unexpectedly, however, it also controls the short-day-induced growth cessation and bud set occurring in the fall. This regulatory mechanism can explain the ecogenetic variation in a highly adaptive trait: the critical daylength for growth cessation displayed by aspen trees sampled across a latitudinal gradient spanning northern Europe.

Reproductive physiology of mango

“…The protein product of FT acts as the florigenic component, that is translocated to Arabidopsis buds (Corbesier et al, 2007). This conclusion is supported by translocation from leaves to buds of an analogous protein encoded by Hd3a, a rice ortholog of FT, which appears to be the florigen operating in that crop (Tamaki et al, 2007), and the aspen ortholog, PtFT1, which along with CONSTANS was demonstrated to regulate the timing of flowering and growth cessation of Populus trichocarpa (Bohlenius et al, 2006). Once translocated to buds, the protein product of FT is thought to combine with the bZIP transcription factor (FD) protein to activate transcription of floral identity genes, such as APETALA1 (AP1) to begin floral expression (Abe et al, 2005;Wigge et al, 2005).…”

Local Selection Across a Latitudinal Gradient Shapes Nucleotide Diversity in Balsam Poplar, Populus balsamifera L

“…In balsam poplar, our analyses implicate FRI in the response to local selection at different latitudes, probably reflecting a role of FRI in the temperaturesensitive timing of seasonal development. Because floweringtime homologs in Populus can affect a range of developmental traits, including flowering and bud dormancy (Böhlenius et al 2006;Ingvarsson et al 2008;Lagercrantz 2009;Ma et al 2010), the link between allelic variation in FRI and variation in specific phenotypes in poplar awaits further study.…”

“…In contrast to the very high levels of segregating variation in Populus LFY, Arabidopsis LFY harbors low diversity consistent with a recent selective sweep . The protease-encoding EARLY BOLTING IN SHORT DAYS (EBS) that regulates the transition from juvenile to reproductive maturity in Populus through transcriptional control of FT (Böhlenius et al 2006) also showed an excess of north-south differentiation.…”

“…Comparative research across diverse taxa suggests that this gene network is responsible for variation in multiple phenological traits responsive to photoperiod, including flowering, tuberization, and seasonal dormancy (Lagercrantz 2009). Based upon transgenic and QTL mapping experiments in Populus, genes in this network are also associated with flowering and vegetative bud development in trees (Frewen et al 2000;Chen et al 2002;Böhlenius et al 2006;Ingvarsson et al 2008;Jackson 2009;Ma et al 2010;Rohde et al 2010).…”

“…Surveys of natural allelic variation among A. thaliana accessions sampled from diverse latitudes have identified two flowering-time genes, FRIGIDA (FRI) and FLOWERING LOCUS C (FLC), that show evidence of local adaptation with latitude (Caicedo et al 2004;Stinchcombe et al 2004;Le Corre 2005). In other species, local selection has targeted members of the phytochrome gene family (PHYE) in Cardamine japonica (Ikeda et al 2009) and PHYB2 in Populus tremula (Ingvarsson et al 2006;Ingvarsson et al 2008) and components of the circadian clock (Böhlenius et al 2006;Slotte et al 2007;Brachi et al 2010;Ma et al 2010). These studies suggest that homologs of the A. thaliana flowering-time gene network underlie ecologically important adaptive variation in phenological responses in other species, making them promising candidates for studying the molecular basis of local adaptation, as well as testing the repeatability of evolution across taxa in genes that influence quantitative traits.…”