Small vs. large

Wider research contextGenome size is known to vary greatly across organisms. For eukaryotes in general, genome size differsalmost 70,000-fold; genome size in angiosperms still varies > 2,400-fold. Although a number of correlationsof genome size with cytological, morphological, and physiological traits have been identified, we largely lackunderstanding of the evolutionary drivers and the functional consequences of the extreme diversity ingenome sizes. Genome size is assumed to affect plant growth, i.e. an increase in genome size results inreduced relative growth rates, though contrasting results have been reported. Recent studies suggest thatthe relationship between genome size and relative growth rate is a function of nutrient supply.ObjectivesExplicitly testing the functional role of genome size on plant growth in dependence of nutrient supply iscentral to the proposed research. Specifically, I will test the following key hypotheses:H1 The relationship between genome size and growth efficiency, i.e. relative growth rate, depends onnutrient supply.H2 The relationship between genome size, relative growth rate and nutrient supply is particularly expressedin closely related species.H3 Disproportional scaling of RNA content with genome size, higher RNA: DNA ratios, explain higherrelative growth rates in large genome size species under replete nutrient conditions.H4 Cellular allocation of phosphorous to RNA is independent of nutrient regime, but in dependence ofgenome size links genome size to the “Growth Rate Hypothesis”.H5 In species with similar genome size, ploidy level has a stronger effect on relative growth rate thanabsolute genome size.Approach/methodsI will conduct a series of plant growth experiments with in total 140 plant species from five families,manipulating nutrient supply in a factorial design. The proposed research joins several state-of-the-artmethods, DNA and RNA analyses, ecological stoichiometry, phylogenetic comparative analyses and traitbased approaches to obtain an inter-disciplinary and comprehensive understanding of the role of a keyenvironmental factor (nutrient availability) on the genomic base of physiological responses in plants.Level of originality / innovationThe project provides a timely opportunity to address fundamentally new questions on the relationshipbetween genome size and plant growth. Particularly, I aim to reveal the underlying cellular, molecular andstoichiometric mechanisms shaping this relationship. Studying this hitherto unexplored and potentiallygeneral ecological concept (H1) will open a new field of investigation and a new level of understandingregarding the genomic base of physiological responses in plants. By providing information on responses ofplants to different nutrient regimes, the research is also relevant in the view of environmental change.Primary researchers involvedLilian-Lee Müller-Fischer, PI; Wolfgang Wanek, Mentor