Conservation of Arabidopsis Flowering Genes in Model Legumes  

Abstract

The model plants Arabidopsis (Arabidopsis thaliana) and rice (Oryza sativa) have provided a wealth of information about genes and genetic pathways controlling the flowering process, but little is known about the corresponding pathways in legumes. The garden pea (Pisum sativum) has been used for several decades as a model system for physiological genetics of flowering, but the lack of molecular information about pea flowering genes has prevented direct comparison with other systems. To address this problem, we have searched expressed sequence tag and genome sequence databases to identify flowering-gene-related sequences from Medicago truncatula, soybean (Glycine max), and Lotus japonicus, and isolated corresponding sequences from pea by degenerate-primer polymerase chain reaction and library screening. We found that the majority of Arabidopsis flowering genes are represented in pea and in legume sequence databases, although several gene families, including the MADS-box, CONSTANS, and FLOWERING LOCUS T/TERMINAL FLOWER1 families, appear to have undergone differential expansion, and several important Arabidopsis genes, including FRIGIDA and members of the FLOWERING LOCUS C clade, are conspicuously absent. In several cases, pea and Medicago orthologs are shown to map to conserved map positions, emphasizing the closely syntenic relationship between these two species. These results demonstrate the potential benefit of parallel model systems for an understanding of flowering phenology in crop and model legume species.The change from vegetative to reproductive growth is a critical developmental transition in the life of a plant, and the induction, expression, and maintenance of the flowering state are regulated by many external and endogenous factors. A vast number of applied and fundamental studies have demonstrated the importance of light (through daylength and light-quality effects) and temperature (through vernalization and ambient temperature effects) as the main environmental regulators of flowering. However, other factors, including nutrient status, endogenous hormones, stress, and the developmental state of the plant, can also be important. Even with respect to light and temperature, great diversity in responsiveness exists within and between different plant species. These differences are important in the adaptation of species to particular latitudinal and climatic regions, and have also been extremely important for determining the environments and agronomic regimes under which crop species can be most effectively grown.The flowering process has been subject to detailed genetic analysis in Arabidopsis (Arabidopsis thaliana). As a small, weedy annual, Arabidopsis is responsive to a wide range of factors and has been invaluable in outlining the major genetic pathways that are likely to function in the control of flowering responses to photoperiod, vernalization, and hormone responses (Amasino, 2004;Boss et al., 2004;Putterill et al., 2004). It is likely that many of the genetic mechanisms discovered in Arabidopsis ...

VEGETATIVE1 is essential for development of the compound inflorescence in pea

“…To identify a candidate gene for VEG1, we adopted a comparative mapping strategy using the related model legume Medicago truncatula, which has inflorescence architecture identical to pea 21 . The VEG1 locus was initially observed to map to the bottom of pea linkage group V (top of Medicago chromosome 7), near the MADS-box gene PsSEPAL- LATA1 (PsSEP1) 22 , and we found that this gene was deleted in veg1. However, consistent with the well-documented role for SEP genes in floral organ identity 23 4a).…”

In silico prediction of gene expression patterns in Citrus flavedo

“…Together with the 10,429 singletons, we conclude that 13,281 expressed sequences are exclusive from flavedo and could be considered as candidates to flavedo-specific genes. Indeed, in silico EST sequence analysis has been used to identify tissue-specific genes in diverse plant species (Figueiredo et al, 2001;Dornelas and Rodriguez, 2004;Hecht et al, 2005;Laitinen et al, 2005;. When ESTs are generated from nonnormalized cDNA libraries, gene expression patterns normally can be inferred from the relative abundance of these sequences among different libraries (Ewing et al, 1999) and the indication of tissue-specific sequences is based on a simplified rule.…”

TheFragaria vescaHomolog of SUPPRESSOR OF OVEREXPRESSION OF CONSTANS1 Represses Flowering and Promotes Vegetative Growth

“…In Arabidopsis, four major genetic pathways (i.e., the photoperiodic, vernalization, autonomous, and gibberellin [GA] pathways) regulate flowering time (Simpson, 2004;Turck et al, 2008;Kim et al, 2009;Mutasa-Göttgens and Hedden, 2009). Many genes with sequence similarity to known flowering genes are found in different plant families, but their functions may differ between species (Suárez-López et al, 2001;Hayama et al, 2003;Hecht et al, 2005Hecht et al, , 2011Mouhu et al, 2009). In perennials, which undergo repeated cycles of vegetative and reproductive phases, flowering time is controlled by seasonal regulation of flowering genes (Böhlenius et al, 2006;Wang et al, 2009;Koskela et al, 2012).…”