Minisymposium 20: Photomorphogenesis

Abs # 41004: De-etiolation is regulated by subtle temperature signals

Presenter:	Finlayson, Scott A, sfinlayson@tamu.edu
Authors	Finlayson, Scott A (A)   Salzman, Ron A (B)   Mullet, John E (B)   Morgan, Page W (A)
Affiliations:	(A): Department of Soil and Crop Sciences, Texas A&M University (B): Department of Biochemistry and Biophysics, Texas A&M University

Environmental cues have a major impact on the growth and development of plants. Plant responses to these conditioning signals determine, in part, the ultimate form and function of the organism. For instance, the response of dark grown plants to subtle light signals is de-etiolation. Although plant responses to subtle light signals have been studied in detail, little is known of the effects of subtle temperature signals on plant growth and development. We have found that de-etiolation, which is typically believed to be controlled by light, is similarly regulated by subtle temperature cues. Temperature signals are sufficient to induce the inhibition of mesocotyl elongation and promote leaf development. The grass crops sorghum and maize are particularly sensitive to these signals and show robust responses amenable to physiological, molecular and genetic analyses. We have characterized some of the parameters of the temperature sensing phenomenon and have found that with respect to both duration and magnitude of the signal the response approximates a hyperbola. As little as a 2 degree differential or 10 minute exposure can produce a measurable effect. The sensitivity and saturable nature of the response support the hypothesis that the phenomenon may be sensor mediated. Our studies indicate that temperature signals can elicit a greater de-etiolation effect than the phytochrome B low fluence response. The effects of low fluence red light and temperature signals delivered concurrently are additive. Temperature sensing and light sensing appear to operate via signaling pathways that are initially independent, but eventually converge to cause similar morphological changes. The phyB mutant sorghum responds to temperature signals like the wild type, indicating that this photoreceptor is not involved in the process. Expression profiling has identified a number of genes with altered expression to subtle temperature signals. Some of these genes are regulated only by temperature signals while others are regulated by both temperature and light signals. The putative temperature sensor(s) may act in concert with light sensors to ensure that de-etiolation occurs upon emergence from the soil.