Understanding how individuals and populations respond to environmental change is a topic of high ecological importance, especially given rapid and ongoing climate change. Plants respond to environmental change in many ways, including changes in gene expression, physiology and morphology. However, changes at the genetic level are especially important given that they occur rapidly and ultimately determine the ability of a species to cope with environmental change. Also, such variation among plant species in their ability to respond to environmental change can ultimately have consequences for plant community structure and can lead to differences in range limits among taxa.
Recent advances in genomic technology have led to an explosion of studies that explore patterns of gene expression in response to different environmental changes. However, most of these studies have been carried out under very controlled conditions, and hence very little is known about genomic responses of plants to environmental change under natural field conditions, which might differ from those found under more controlled conditions. In their paper Variation in gene expression of Andropogon gerardii in response to altered environmental conditions associated with climate change Travers and colleagues measured transcriptional profiles of individuals of Andropogon gerardii (a native C4 grass of North American grasslands) in a long-term climate change experiment at Konza Prairie, USA, in which both temperature and precipitation had been manipulated since 1998 to simulate predicted climate change, in particular warming (ambient or warmed by c. 2 ˚C) and prolonged periods of drought. Using microarrays developed for the closely related model species Zea mays, the authors analysed the relative effects of warming and altered soil moisture availability on the expression levels of over 7000 genes of A. gerardii, which allowed them to pin-point responsive functional groups of genes and correlate changes in gene transcription with physiological responses of the grass to climate manipulations.
Using this approach, they found that transcriptional profiles of A. gerardii had changed in response to climate manipulations, but that far more genes responded to warming than to changes in soil moisture availability. Also, they found that transcriptional profiles of A. gerardii responded differently to the combined effects of warming and reduced water availability than to either of these environmental factors alone. This finding indicates that multiple stressors are likely to play a significant role in determining plant genetic responses to climate change, which supports a growing awareness among ecologists that prediction of future responses of ecosystems to global change demands a greater understanding of the simultaneous effects of multiple global change drivers. Another important finding was that candidate genes were identified which demonstrated transcription levels closely associated with physiological variables, in particular chlorophyll fluorescence. As suggested by the authors, these changes in gene expression might be indicative of a mechanism for the well established reduction in photosynthetic capacity of A. gerardii under the environmental stress of warming and prolonged drought.
This study of Travers and colleagues is among the first to investigate expression patterns and their relationships to environmental factors and physiological responses in an ecologically important and widespread grassland species in the field. Moreover, the results of this study indicate that this species responds differently to different aspects of predicted climate change, and that these genetic responses have the potential to influence phenotypic characters and, ultimately, adaptive responses to climate change. As noted by the authors, however, the influence of selection on the candidate genes identified in this study, and also the long-term population responses of A. gerardii to climate change, will depend on how the detected shifts at the genomic level translate to changes in growth, reproduction and survivorship of individuals.
Editor, Journal of Ecology
- Travers, S.E., Tang, Z., Caragea, D., Garrett, K.A., Hulbert, S.H., Leach, J.E., Bai, J., Saleh, A., Knapp, A.K., Fay, P.A., Nippert, J., Schnable, P.S., Smith, M.D. (2010) Variation in gene expression of Andropogon gerardii in response to altered environmental conditions associated with climate change. Journal of Ecology, 374-383.
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