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Annual plants complete their life cycle in one year and initiate flowering only once, whereas perennials live for many years and flower repeatedly. How perennials undergo repeated cycles of vegetative [...]

Genome sequencing of the model legumes, Medicago truncatula and Lotus japonicus, provides an opportunity for large-scale sequence-based comparison of two genomes in the same plant family. Here we report synteny comparisons between these species, including details about chromosome relationships, large-scale synteny blocks, microsynteny within blocks, and genome regions lacking clear correspondence. The Lotus and Medicago genomes share a minimum of 10 large-scale synteny blocks, each with substantial collinearity and frequently extending the length of whole chromosome arms. The proportion of genes syntenic and collinear within each synteny block is relatively homogeneous. Medicago-Lotus comparisons also indicate similar and largely homogeneous gene densities, although gene-containing regions in Mt occupy 20-30% more space than Lj counterparts, primarily because of larger numbers of Mt retrotransposons. Because the interpretation of genome comparisons is complicated by large-scale genome duplications, we describe synteny, synonymous substitutions and phylogenetic analyses to identify and date a probable whole-genome duplication event. There is no direct evidence for any recent large-scale genome duplication in either Medicago or Lotus but instead a duplication predating speciation. Phylogenetic comparisons place this duplication within the Rosid I clade, clearly after the split between legumes and Salicaceae (poplar). polyploidy | synteny | genome duplication

Two gene groups form a feedback loop in the meristem of Arabidopsis. The CLAVATA1, 2, and 3 (CLV) genes inhibit the WUS gene, which induces meristem cell identity and expression of CLV3.

A molecular analysis of the WUS gene from the Arabidopsis plant was performed to determine its function in shoot and floral meristems. The subcellular localization of the WUS protein was identified utilizing a translational fusion between WUS and the Glucoronidase reporter gene in transient expression assays. It was revealed that pluripotent cell fate during embryonic shoot meristem development necessitated the presence of WUS expression and that WUS represented a novel subtype of homeodomain proteins acting as transcription regulators.