Acclimation and Sustainable Plant Productivity
Dr. Norman Hüner & Dr. Bernard Grodzinski
The Biotron will enable researchers to accelerate our understanding of terrestrial and aquatic organisms' responses to climate change. This knowledge will be used not only to develop crops with enhanced capacity to adjust to and resist the stress effects of climate change but also to develop crops that exhibit the potential for higher yields per hectare than currently possible under environmental stress conditions typically associated with climate change such as increased CO2 concentrations, unusually broad temperature fluctuations, drought, poor soil nutrients and elevated UV levels.
A defining characteristic of all life is the ability to couple energy flow (i.e. thermodynamics) through the biological system to the maintenance of its homeostasis, that is, maintenance of a metabolic balance between interdependent processes, cellular compartments, tissues and organs within a single organism. The capacity of terrestrial and aquatic photosynthetic organisms to adjust or acclimate to an environment that is constantly changing with respect to temperature, light, CO2, and nutrient status on a daily as well as a seasonal basis, is dependent upon two important factors.
First, the actual genetic make-up or genotype of the plant determines the potential of any species to acclimate. Second, the capacity to regulate the expression of this genome in response to environmental cues such as light, temperature and water status reflects the remarkable flexibility or plasticity that a single species can exhibit with respect to form and function, that is, phenotype. Although both factors are inextricably linked, it is the capacity to alter form and function that governs plant productivity in a changing environment. Greater phenotypic plasticity in response to any environmental stress usually results in increased plant productivity under the stress condition.
The approach to understanding plant acclimation and biomass production used by the Hüner / Grodzinski group is novel and innovative because, in contrast to the strictly genomic approach, their approach is phenotypically based and focused on the elucidation of the mechanisms linking energy sensing and energy conversion to the regulation of plant form, function and biomass. Light is the ultimate source of energy used to create plant biomass through the conversion of CO2 in the air to stable carbohydrates such as sugars.
In addition to acting as the principal energy transformer, the photosynthetic apparatus of organisms as diverse as algae, cyanobacteria, wheat, pine trees and the model plant, Arabidopsis thaliana, also acts as a global, environmental redox sensor which senses changes in cellular energy budget. Hüner and collaborators discovered that this remarkable photosynthetic sensor not only controls the expression of chloroplastic and nuclear photosynthetic genes, it also controls nuclear genes involved in processes as diverse as cold acclimation and plant morphology, that is, plant shape.
Hüner and collaborators have shown that exposure to any environmental stress singly or in combination (temperature, light, drought, UV radiation, nutrient status) causes an energy overload or 'excitation pressure'. The redox sensor detects alterations in excitation pressure. Hüner and collaborators were the first to discover that specific crop plants such as wheat and rye respond to high excitation pressure by increasing their biomass production due to a global reprogramming of the metabolism, growth and development.
Although the Hüner/Grodzinski group has identified the a critical sensor that signals this metabolic reprogramming, the underlying mechanism by which this sensor/signal affects this complex, global regulation of plant carbon metabolism and biomass production is presently unknown. The hypothesis is that the photosynthetic redox energy sensor itself is one of possibly several critical, initial molecular switches that regulate this global reprogramming of carbon metabolism and biomass production under stress conditions.
The scope of the research endeavor required to elucidate this hypothesis transcends traditional levels of scientific collaboration and co-operation since it necessitates the integration of expertise as diverse as thermodynamics, photochemistry, biochemistry/physiology, genomics, proteomics, metabolomics, mathematical modeling, modern plant molecular biology and traditional plant breeding as well as controlled environment scale and flexibility. This group has already identified natural germplasm in wheat, rye, tomato and Arabidopsis that exhibit the characteristic global reprogramming of metabolism, growth and biomass production upon exposure to environmental stress such as temperature. In addition, the first of a set of novel wheat and rye excitation pressure genes have been identified and characterized which will be used to assess their role(s) in cellular global redox sensing/signaling. These plants and genes will be exploited genetically, biochemically, and physiologically to unravel the links between global energy sensing/signaling and biomass production.
The Hüner/Grodzinski group have the necessary expertise in place through long-term national (Toronto, Guelph, Queen�s, Agriculture & Agri-Food Canada (AAFC), Ottawa, UQAM, Saskatoon) and international (Umea University, Biosphere 2 Laboratory, Iowa State Univ., Univ. Bielefeld, Germany) collaborators. The scale and the environmental flexibility of the controlled growth facilities available at the Biotron will create the catalyst that will enable this unprecedented integration by providing the infrastructure not only to elucidate the underlying molecular mechanism of global regulation of plant biomass production but also to assess the impact of long-term changes in environmental conditions such as CO2, temperature, light, water availability and UV levels, singly or in combination, on this global regulatory process.
Seasonal extremes in climate will continue to have a negative impact on plant productivity and Canada's 130 billion-dollar per year agriculture and forest industries. Thus, this research will have a significant impact on the ability of Canada and the world to sustain agricultural and forestry production under suboptimal growth conditions as a consequence of global climate change.
