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A. alpina is a Brassicaceae species and perennial relative of the annual model Arabidopsis thaliana. Comparative studies between these two models have been successful in tracing at the molecular level the mechanisms that contributed to the diversification of the annual and perennial life strategies. Differences in flowering behavior between annual and perennial species contribute to differences in their life strategy. A text book example is the role of FLOWERING LOCUS (FLC) in life history evolution of A. alpina and A. thaliana. FLOWERING LOCUS C (FLC) is a key floral repressor in A. thaliana that regulates flowering in response to vernalisation. Its orthologue in A. alpina, PERPETUAL FLOWERING 1 (PEP1) also ensures flowering in response to vernalisation but in addition contributes to perennial traits such as polycarpic growth habit and the duration of the flowering episode. pep1 mutants flower without vernalisation and show reduced return to vegetative growth. My group is studying the regulation of inflorescence development and outgrowth in perennials using A. alpina as a model. We performed an enhancer screen of the pep1-1 mutant and isolated several second-site mutants that show inflorescence phenotypes. Mapping by sequencing of several mutants reveal a novel regulator not previously studied in A. thaliana. [mehr]

The induction of flowering is a central event in the life cycle of plants. When timed correctly, it helps ensure reproductive success, and therefore has adaptive and economic value: precocious flowering often results in reduced yield, both in biomass and fruits, whereas a delay in flowering can result in an increase of biomass. However, the latter is usually accompanied by reduced seed set or seed filling, limiting the use of late-flowering varieties in agronomics. Because of its importance, flowering is under the control of a complex genetic circuitry that integrates endogenous signals such as hormonal and carbohydrate status, and environmental signals such as temperature and light. Genetic analyses had initially suggested the existence of genetically defined pathways that regulate flowering in response to a specific input. Over the last several years, however, it has become apparent that many important flowering time genes are not regulated by single inputs, but rather integrate multiple, often contradictory signals to control the induction of flowering. I will discuss our recent findings on different flowering time pathways in Arabidopsis thaliana and dynamic changes of the chromatin landscape at the shoot apical meristem during the floral transition. [mehr]

Multicellular organisms develop by integrating and coordinating multiple growth programs. In plants, a paradigm for such systems is the secondary growth (thickening) of stems and roots. Secondary growth provides the mechanical support and stability that plants need to expand their longitudinal growth, to generate new growth axes in the form of branches and to sustain new structures such as fruits, leaves or flowers. In addition to playing a crucial role in plant development, secondary growth is of relevant social and economic importance. First, in trees, secondary growth brings about wood: one of the largest sources of terrestrial biomass, the largest sink of atmospheric CO2 after oceans and a main source of raw material for the renewable energy, construction, timber, paper or pulp industries. Second, in terms of agriculture, secondary growth is key for determining crop architecture and properties. Secondary growth is the result of the formation of secondary vascular tissues (secondary xylem and secondary phloem). The secondary vascular tissues develop through the activity of a highly specialized pool of stem cells (meristem) termed cambium. In our lab we focus mainly in (i) the genetic regulation of cellular proliferation within the cambium and (ii) the impact of cambium-mediated cell fate determination on organ architecture. We use specific plant species depending on the actual question to be addressed. In my talk I will summarize our work in Arabidopsis thaliana (which we use as an example to study cellular proliferation in the cambium) and in Manihot esculenta (Cassava), which we use as an example to understand the impact of cell fate determination on organ architecture. Due to the social relevance of Cassava, potential applications of our work will be discussed. [mehr]