RESUMO
A novel EMBRYONGIC FLOWER2 gene, DlEMF2, was isolated from bamboo, Dendrocalamus latiflorus. It is 2518 bp in length encoding a protein of 629 amino acids. It was expressed in all organs and at a higher level in shoot tissue than in inflorescences. Transgenic Arabidopsis plants expressing antisense DlEMF2 displayed a spectrum of early-flowering phenotypes. Quantitative real-time PCR experiments indicated that the antisense transgene DlEMF2 reduced endogenous AtEMF2 transcript levels leading to the flowering time reduction. Besides, transforming the bamboo DlEMF2 gene into Arabidopsis emf2-1 mutant could rescue phenotype in vegetative and reproductive developmental stages, which reveals that EMF2 has functional conservation between monocots and eudicots.
Assuntos
Proteínas de Arabidopsis/genética , Arabidopsis/genética , Sequência Conservada , Poaceae/genética , Proteínas Repressoras/genética , Sequência de Aminoácidos , Proteínas de Arabidopsis/antagonistas & inibidores , DNA de Plantas/química , DNA de Plantas/genética , Perfilação da Expressão Gênica , Inativação Gênica , Dados de Sequência Molecular , RNA Antissenso/genética , RNA Antissenso/metabolismo , Proteínas Repressoras/antagonistas & inibidores , Reação em Cadeia da Polimerase Via Transcriptase Reversa , Alinhamento de Sequência , Análise de Sequência de DNARESUMO
Arabidopsis VERNALIZATION2 (VRN2), EMBRYONIC FLOWER2 (EMF2), and FERTILIZATION-INDEPENDENT SEED2 (FIS2) are involved in vernalization-mediated flowering, vegetative development, and seed development, respectively. Together with Arabidopsis VEF-L36, they share a VEF domain that is conserved in plants and animals. To investigate the evolution of VEF-domain-containing genes (VEF genes), we analyzed sequences related to VEF genes across land plants. To date, 24 full-length sequences from 11 angiosperm families and 54 partial sequences from another nine families were identified. The majority of the full-length sequences identified share greatest sequence similarity with and possess the same major domain structure as Arabidopsis EMF2. EMF2-like sequences are not only widespread among angiosperms, but are also found in genomic sequences of gymnosperms, lycophyte, and moss. No FIS2- or VEF-L36-like sequences were recovered from plants other than Arabidopsis, including from rice and poplar for which whole genomes have been sequenced. Phylogenetic analysis of the full-length sequences showed a high degree of amino acid sequence conservation in EMF2 homologs of closely related taxa. VRN2 homologs are recovered as a clade nested within the larger EMF2 clade. FIS2 and VEF-L36 are recovered in the VRN2 clade. VRN2 clade may have evolved from an EMF2 duplication event that occurred in the rosids prior to the divergence of the eurosid I and eurosid II lineages. We propose that dynamic changes in genome evolution contribute to the generation of the family of VEF-domain-containing genes. Phylogenetic analysis of the VEF domain alone showed that VEF sequences continue to evolve following EMF2/VRN2 divergence in accordance with species relationship. Existence of EMF2-like sequences in animals and across land plants suggests that a prototype form of EMF2 was present prior to the divergence of the plant and animal lineages. A proposed sequence of events, based on domain organization and occurrence of intermediate sequences throughout angiosperms, could explain VRN2 evolution from an EMF2-like ancestral sequence, possibly following duplication of the ancestral EMF2. Available data further suggest that VEF-L36 and FIS2 were derived from a VRN2-like ancestral sequence. Thus, the presence of VEF-L36 and FIS2 in a genome may ultimately be dependent upon the presence of a VRN2-like sequence.
