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Molecular Analysis of Adaptive Responses in Plants

Tapio Palva
Academy professor Department of Biosciences,
Div. of Genetics and Institute of Biotechnology

phone +358-9-191 59600 fax +358-9-191 59076,

Research Profile
Our work is focused on addressing one of the central questions in plant biology: how do plants respond and adapt to their environment? A multidisciplinary approach including molecular, genetic, biochemical and physiological studies as well as a heavy emphasis on functional genomics is employed to understand the molecular mechanisms of this adaptation and to apply this knowledge to plant breeding. Plant growth, distribution and productivity as well as product quality is greatly influenced by the environmental stresses plants are continuously exposed to. The optimal growth and development is far from that realized in the field or in the forest. Plants as sessile organisms have developed various sophisticated ways to react to the changes in the environment by altering their metabolism accordingly. Effective responses to external and internal stimuli will ensure optimal growth and survival in an environment where the plant is continuously challenged by both abiotic and biotic stresses. We employ two plant models for these studies Arabidopsis and birch. The aim of our research is to elucidate: the fundamental biological processes that govern plant responses and adaptations to its environment, the molecular communication involved in such responses as well as ascribe a function to the response proteins and other molecules involved. To this aim we will:(i) Dissect signal processes involved in plant responses to environmental stimuli such as cold and drought, photoperiod and pathogens. (ii) Characterize the role and interaction of plant signal molecules/hormones such as ABA, GA, JA, ROS, SA, and ethylene in these responses. (iii) Ascribe a function to stress response proteins and utilize this information for improving stress tolerance by providing molecular markers for breeding or by engineering stress tolerance.

Cold acclimation and development of freezing and drought tolerance
The main limitation in plant growth, productivity and distribution is due to environmental stresses leading to cellular water deficit such as freezing, drought and high salinity. Our aim is to understand the molecular mechanisms involved in stress adaptation and stress tolerance using Arabidopsis as the main model. Exposure of Arabidopsis as well as other temperate plants to low nonfreezing temperatures triggers cold acclimation resulting in development of freezing tolerance. Cold acclimation is accompanied by expression of specific low temperature induced genes that are thought to encode proteins required for frost tolerance. We have previously isolated and characterized a number of Arabidopsis genes that are responsive to low temperature, drought and the phytohormone ABA and shown the presence of distinct signal pathways leading to their activation. This has provided us with the tools required to understand the cold acclimation process in detail. The work is focused on two types of studies: (i) elucidation of the signal perception and transduction processes leading to cold acclimation in both Arabidopsis and birch and (ii) functional studies of the response genes and proteins as well as engineering stress tolerance. This is achieved by genetic and biochemical approaches as well as extensive use of functional genomics. The information obtained is utilized for developing plants with enhanced tolerance to freezing and drought stress.

Control of tree growth and hardiness
Effective stress responses are central to plant life, particularly for woody species with long life spans such as birch. The aim of our research is to elucidate the molecular mechanisms that control stress adaptation and tree growth in boreal forests and apply this knowledge for tree breeding using birch (Betula pendula) as our main model. Central to this research is to elucidate the function of gene products that control growth of trees in boreal climates governed by a special combination of light and temperature. The focus is on elucidating the molecular mechanisms of photoperiod perception and development of dormancy and winter hardiness in birch. The genetically and physiologically well characterized photoperiod ecotypes and their progenies will form the basis for this work. We are currently characterizing the birch genome as an essential tool for both basic and applied studies. This is done by large scale automated sequencing and functional analysis of ESTs (Expressed sequence tags), such as ESTs related to stress responses and plant growth control. The birch EST program has so far resulted in identification of over 30 000 ESTs and will allow us to obtain a representative collection of target and regulatory genes diagnostic to control of growth and hardiness. The functional assignment of the genes will be by expression profiling using microarrays and generation of transgenic plants (both birch and Arabidopsis).

Plant defense responses
Plants have effective means in defending themselves against invading pathogens. The main components of these defenses are the induced responses triggered by recognition of the pathogen and providing both local and systemic resistance to the pathogen. We employ the nonspecific bacterial pathogen Erwinia carotovora as our pathogen model and Arabidopsis as our main model plant (others being birch and potato). Our aim is to elucidate the molecular communication between the plant and the pathogen both in a compatible and in an incompatible interaction. Recent studies have defined the most informative target genes for studies of this response. Use of pathway specific target genes and signal mutants have proven instrumental for these studies. The functional assignment of selected target and regulatory genes will be by overexpression/antisense silencing in transgenic plants and isolation of signal mutants with the help of a "mutant machine" Current work is focused on elucidation of the nature of elicitors and suppressors of plant defense produced by the pathogen, their recognition by the plant host and characterization of the signal pathways required for defense gene activation and induction of both local and systemic disease resistance. Ultimately, when we have a better understanding of the events in these responses, this knowledge can be used to improve disease resistance and for designing novel strategies for disease management in future agriculture and forestry.

Academy of Finland, Biocentrum Helsinki, EU, Technology Development Centre (TEKES) 3


Selected Publications


Last update 26.06.2001 Maintained by Webmaster