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Chapter Thirteen - Plant secondary metabolite polymorphisms and the extended chemical phenotype
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- By Glenn R. Iason, Ecological Sciences Group, The James Hutton Institute, Ben D. Moore, Ecological Sciences Group, The James Hutton Institute, Jack J. Lennon, Ecological Sciences Group, The James Hutton Institute, Jenni A. Stockan, Ecological Sciences Group, The James Hutton Institute, Graham H. R. Osler, Ecological Sciences Group, The James Hutton Institute, Colin D. Campbell, Ecological Sciences Group, The James Hutton Institute, David A. Sim, Ecological Sciences Group, The James Hutton Institute, Joan R. Beaton, Ecological Sciences Group, The James Hutton Institute, Joanne R. Russell, The James Hutton Institute
- Edited by Glenn R. Iason, Marcel Dicke, Wageningen Universiteit, The Netherlands, Susan E. Hartley, University of York
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- Book:
- The Ecology of Plant Secondary Metabolites
- Published online:
- 05 August 2012
- Print publication:
- 19 April 2012, pp 247-268
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Summary
Introduction
As it was originally proposed, the extended phenotype comprised ‘all effects of a gene upon the world’ (Dawkins, 1989) and portrayed how the effects of a gene borne by an organism influenced its biotic and abiotic environments. The consideration of indirect genetic effects, in which an organism’s phenotype becomes part of the selective environment of conspecifics (Wolf et al., 1998), was developed rigorously in the population genetics context and the concept subsequently extended to include effects on heterospecifics (Whitham et al., 2003). The extended phenotype concept has been adopted as a framework by some evolutionary biologists and ecologists to study the roles of plant secondary metabolites (PSMs) since Whitham et al. (2003) used heritable variation in tissue tannin concentrations among Populus species and hybrids to develop the concept of community and ecosystem genetics (Antonovics, 1992).
Many studies of how genetically determined variation in plant traits, including PSMs, drive associated community phenotypes and processes, have been based on differences between hybrids (Dungey et al., 2000; Hochwender & Fritz, 2004; Bailey et al., Chapter 14). Fewer studies have investigated the effects on extended phenotypes of continuously varying PSMs or between known genotypes within a species (Whitham et al., 2006; Schweitzer et al., 2008; Barbour et al., 2009; O’Reilly-Wapstra et al., Chapter 2). A convenient approach to identification and utilisation of genotypic variation for the study of multiple effects of PSMs is provided by the use of genetic polymorphisms. A polymorphism can be defined as occurring when a trait such as a morphological or biochemical character exists in two or more distinct forms in a randomly mating population within a species (Ford, 1975). The approach is particularly useful in species that cannot be readily cloned. Here, we review examples of how intra-specific variation in a particular group of PSMs, the monoterpenes, has informed our understanding of how PSMs can play multiple ecological roles and mediate the extended phenotype of plants. The monoterpenes are a group of low-molecular-weight, volatile terpenoids which form a very diverse group in terms of number of compounds, structure and function (Gershenzon & Dudareva, 2007). We use variation within species which are polymorphic for concentrations or presence of monoterpenes to provide an insight into their ecological ramifications and larger-scale consequences, against the background of intra-specific variation in other traits.
Residual photosensitivity in mice lacking both rod opsin and cone photoreceptor cyclic nucleotide gated channel 3 α subunit
- ALUN R. BARNARD, JOANNE M. APPLEFORD, SUMATHI SEKARAN, KRISHNA CHINTHAPALLI, AARON JENKINS, MATHEAS SEELIGER, MARTIN BIEL, PETER HUMPHRIES, RON H. DOUGLAS, ANDREAS WENZEL, RUSSELL G. FOSTER, MARK W. HANKINS, ROBERT J. LUCAS
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- Journal:
- Visual Neuroscience / Volume 21 / Issue 5 / September 2004
- Published online by Cambridge University Press:
- 01 September 2004, pp. 675-683
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The mammalian retina contains three classes of photoreceptor. In addition to the rods and cones, a subset of retinal ganglion cells that express the putative sensory photopigment melanopsin are intrinsically photosensitive. Functional and anatomical studies suggest that these inner retinal photoreceptors provide light information for a number of non-image-forming light responses including photoentrainment of the circadian clock and the pupil light reflex. Here, we employ a newly developed mouse model bearing lesions of both rod and cone phototransduction cascades (Rho−/−Cnga3−/−) to further examine the function of these non-rod non-cone photoreceptors. Calcium imaging confirms the presence of inner retinal photoreceptors in Rho−/−Cnga3−/− mice. Moreover, these animals retain a pupil light reflex, photoentrainment, and light induction of the immediate early gene c-fos in the suprachiasmatic nuclei, consistent with previous findings that pupillary and circadian responses can employ inner retinal photoreceptors. Rho−/−Cnga3−/− mice also show a light-dependent increase in the number of FOS-positive cells in both the ganglion cell and (particularly) inner nuclear layers of the retina. The average number of cells affected is several times greater than the number of melanopsin-positive cells in the mouse retina, suggesting functional intercellular connections from these inner retinal photoreceptors within the retina. Finally, however, while we show that wild types exhibit an increase in heart rate upon light exposure, this response is absent in Rho−/−Cnga3−/− mice. Thus, it seems that non-rod non-cone photoreceptors can drive many, but not all, non-image-forming light responses.