Molecular Mechanisms of Plant Adaptation

Dr. Roosa Laitinen and her group use natural variants of Arabidopsis thaliana in order to understand the genetic and molecular basis of plant adaptation and evolution. The group’s current research is focused on two main questions. The first is to understand what the different mechanisms of hybrid incompatibilities are and how they explain plant evolution. The second is to find out what is the genetic basis of plasticity and its role in plant responses to changing environments. Addressing these questions necessitates a combination of approaches across different scales, from single genotypes to populations, from the molecular to complex end-phenotypes, and from the greenhouse to the natural habitat and the field.

Diverse mechanisms of hybrid incompatibility in Arabidopsis thaliana

Hybrids sometimes perform worse and show reduced fitness in comparison to their parents. This phenomenon is called hybrid incompatibility and it exists throughout taxa. Hybrid incompatibilities are found both within a species and between species and can occur before or after fertilization. Knowledge of mechanisms that govern this process will deepen our understanding of the first steps towards reproductive isolation and speciation, even before species have diverged. The most common type of post-zygotic hybrid incompatibility in Arabidopsis and other plants is hybrid necrosis, in which hybrid problems are associated with autoactivation of immune responses. Yet, the diversity of the different molecular mechanisms contributing to hybrid incompatibility and the evolutionary forces that maintain the incompatibility alleles in populations, are still largely unknown. In the first line of research, the main focus has been to investigate intraspecific post-zygotic hybrid incompatibility in plants using Arabidopsis as a model system. We take advantage of both publically available Arabidopsis accessions from diverse geographical locations and local accessions that we have collected in recent years. In the past five years, we have identified novel genes required for four new hybrid incompatibility cases highlighting that not only rapidly evolving genes, but also genes involved in conserved processes may underlie hybrid incompatibility. Moreover, we have shown that so far that all of these incompatibility phenotypes are conditional on environmental factors. Currently, we focus on investigating the mechanisms behind four hybrid cases in detail.

Plasticity and trade-offs in Arabidopsis thaliana

The Earth’s temperature is predicted to keep rising and this is expected to increase abiotic and biotic stressors worldwide. To breed more resilient crops, it is crucial to understand both the mechanisms behind adaptive traits and the mechanisms that allow plants to adjust their phenotypes to ensure optimal yields in future environments. The ability of an individual to alter its phenotype in response to different environments is called plasticity. Plasticity is particularly important for sessile plants allowing them to quickly respond to changes in their surroundings and ensuring maximal fitness. In this second line of research, our aim is to understand genetic and molecular mechanisms of plasticity in plants. We are currently pursuing two different projects, in one we study flower size plasticity in response to temperature and in the other multi-trait plasticity in response to nitrogen.

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