The Physiology of Flowering Plants - KHAM PHA MOI

PHYTOCHROME SIGNAL TRANSDUCTION 267Another example is provided by the interaction between theshade-avoidance response and ethylene. Ethylene production insorghum (Sorghum bicolor) is under circadian control, the peak amplitudeof which is strongly increased by shade conditions. A phyBmutant of sorghum that exhibits a constitutive shade-avoidanceresponse also produces much more ethylene than normal, evenwhen grown under full sunlight (Finlayson et al. 1999). In tobacco,Pierik et al. (2003) have demonstrated that many features of theshade-avoidance response can be stimulated by exposing plants toethylene, and that ethylene-insensitive tobacco plants show adelayed shade-avoidance response when grown at high densities orwhen exposed to EOD-FR light. The molecular basis of this interactionis yet to be understood.As auxin and gibberellic acid are important in stimulatingplant growth, it is to be expected that there will be many interactionsbetween these plant growth hormones and light. The interactionof auxin and light in stimulating phototropic curvatures isconsidered further in Chapter 12. The reader is referred to papersby Halliday & Fankhauser and Morelli & Ruberti (see Complementaryreading) for more extensive reviews of photoreceptor–hormoneinteractions.As our understanding of the signal transduction chains of individualphotoreceptors improves, the interactions between them willbecome clearer. The challenge will still remain of integrating thisdetailed molecular information into a broader ecophysiologicalcontext.Complementary readingHalliday, K. J. & Fankhauser, C. Phytochrome-hormonal signalling networks.New Phytologist, 157 (2003), 449–63.Hardtke, C. S. & Deng, X. W. The cell biology of the COP/DET/FUS proteins.Regulating proteolysis in photomorphogenesis and beyond? PlantPhysiology, 124 (2000), 1548–57.Morelli, G. & Ruberti, I. Light and shade in the photocontrol of Arabidopsisgrowth. Trends in Plant Science, 7 (2002), 399–404.Quail, P. H. Phytochrome photosensory signalling networks. Nature Reviews,Molecular Cell Biology, 3 (2002), 85–93.Schwechheimer, C. & Deng, X. W. The COP/DET/FUS proteins: regulators ofeukaryotic growth and development. Seminars in Cell & Developmental Biology,11 (2000), 495–503.Smith, H. Physiological and ecological function within the phytochromefamily. Annual Review of Plant Physiology and Plant Molecular Biology, 46 (1995),289–315.Stern, D. B., Higgs, D. C. & Yang, J. J. Transcription and translation inchloroplasts. Trends in Plant Science, 2 (1997), 308–15.Sullivan, J. A. & Deng, X. W. From seed to seed: the role of photoreceptorsin Arabidopsis development. Developmental Biology, 260 (2003), 289–97.