Plant species have evolved a wide variety of flowering habits, each adapted to maximize reproductive success in their local environment. Even within a species, accessions from different environments can exhibit markedly different flowering behavior. In Arabidopsis, some accessions are rapid-cycling summer annuals, whereas others accessions are late flowering and vernalization responsive and thus behave as winter annuals. Two genes, FLOW-ERING LOCUS C (FLC) and FRIGIDA (FRI), interact synergistically to confer the winter-annual habit. Previous work has shown that many summer-annual accessions contain null mutations in the FRI gene; thus it appears that these summer-annual accessions have arisen from winter-annual ancestors by losing FRI function. In this work we demonstrate that naturally occurring allelic variation in FLC has provided another route to the evolution of summer-annual flowering behavior in Arabidopsis. We have identified two summer-annual accessions, Da (1)-12 and Shakhdara, that contain functional alleles of FRI, but are early flowering because of weak alleles of FLC. We have also determined that the weak allele of FLC found in Landsberg erecta is naturally occurring. Unlike accessions that have arisen because of loss-of-function mutations in FRI, the FLC alleles from Da (1)-12, Shakhdara, and Landsberg erecta are not nulls; however, they exhibit lower steady-state mRNA levels than strong alleles of FLC. Sequence analysis indicates that these weak alleles of FLC have arisen independently at least twice during the course of evolution.FRIGIDA ͉ vernalization ͉ winter annual ͉ natural variation I dentification of the genetic mechanisms that underlie differences in life history is key to understanding the evolution of adaptive traits. Many plants species occur over a wide range of latitudes, and within a species, accessions from different regions can differ substantially in flowering behavior (1). As an adaptation to seasonal fluctuations in temperature experienced in temperate climates, flowering in many species is promoted by prolonged exposure to cold temperatures (vernalization) (2). Many accessions of Arabidopsis from temperate climates are relatively late flowering unless vernalized (3). This vernalization requirement prevents flowering before winter and promotes rapid flowering in the spring, and thus these accessions behave as winter annuals. Summer-annual Arabidopsis accessions, in contrast, flower rapidly in the absence of vernalization, and these accessions predominate in warmer climates that do not experience the cold temperatures required for vernalization (3).The late-flowering phenotype of winter-annual accessions of Arabidopsis is created by the interaction of two genes, FLOW-ERING LOCUS C (FLC) and FRIGIDA (FRI) (2). FLC encodes a MADS domain-containing transcription factor whose expression is sufficient to inhibit flowering (4, 5); however, the native FLC gene is only expressed to high levels in the presence of FRI, which encodes a plant-specific gene of unknown biochemical activity ...

SummaryThe timing of¯owering is important for the reproductive success of plants. Here we describe the identi®cation and characterization of a new MADS-box gene, FLOWERING LOCUS M (FLM), which is involved in the transition from vegetative to reproductive development. FLM is similar in amino-acid sequence to FLC, another MADS-box gene involved in¯owering-time control.¯m mutants are earlȳ owering in both inductive and non-inductive photoperiods, and¯owering time is sensitive to FLM dosage. FLM overexpression produces late-¯owering plants. Thus FLM acts as an inhibitor of¯owering. FLM is expressed in areas of cell division such as root and shoot apical regions and leaf primordia.

BackgroundSugarcane is the source of sugar in all tropical and subtropical countries and is becoming increasingly important for bio-based fuels. However, its large (10 Gb), polyploid, complex genome has hindered genome based breeding efforts. Here we release the largest and most diverse set of sugarcane genome sequences to date, as part of an on-going initiative to provide a sugarcane genomic information resource, with the ultimate goal of producing a gold standard genome.ResultsThree hundred and seventeen chiefly euchromatic BACs were sequenced. A reference set of one thousand four hundred manually-annotated protein-coding genes was generated. A small RNA collection and a RNA-seq library were used to explore expression patterns and the sRNA landscape. In the sucrose and starch metabolism pathway, 16 non-redundant enzyme-encoding genes were identified. One of the sucrose pathway genes, sucrose-6-phosphate phosphohydrolase, is duplicated in sugarcane and sorghum, but not in rice and maize. A diversity analysis of the s6pp duplication region revealed haplotype-structured sequence composition. Examination of hom(e)ologous loci indicate both sequence structural and sRNA landscape variation. A synteny analysis shows that the sugarcane genome has expanded relative to the sorghum genome, largely due to the presence of transposable elements and uncharacterized intergenic and intronic sequences.ConclusionThis release of sugarcane genomic sequences will advance our understanding of sugarcane genetics and contribute to the development of molecular tools for breeding purposes and gene discovery.Electronic supplementary materialThe online version of this article (doi:10.1186/1471-2164-15-540) contains supplementary material, which is available to authorized users.

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