Minisymposium 16: Clocks & Light

Add this abstract to my Itinerary

Abs # M1601: Green Light Regulation of Plastid Transcript Accumulation in Tobacco and Arabidopsis

Presenter:	Dhingra, Amit       Contact Presenter
Authors	Dhingra, Amit  (A)   Bies, Dawn H (A)   Folta, Kevin M. (A) (B)
Affiliations:	(A): Horticultural Sciences Department, University Of Florida (B): Plant Molecular and Cellular Biology Program, University of Florida
Web Site:	http://www.arabidopsisthaliana.com

Green light, a light quality thought to be developmentally benign, can specifically induce responses that counter the normal progression of photomorphogenic development. These responses include an increase in stem elongation, a decrease in early leaf development, and shade-avoidance symptoms in mature plants. One of the green-light specific molecular responses is an acute and robust down-regulation of specific chloroplast transcripts in the etiolated seedling. Most of these transcripts encode proteins required for chloroplast development and function, therefore they are usually described as being up-regulated by light. For example, the steady-state level of psaA and psbD decrease approximately 2-4 fold following a short, single pulse of green light. The decrease is not observed following a blue, red or far-red pulse, and it persists in all photomorphogenic mutants tested, therefore new tools are required to study the response beyond the limits of Arabidopsis thaliana. Tobacco offers a superior system to test biochemistry of the chloroplast. Tobacco also presents the capacity to manipulate the plastid genome, allowing tests of cis-acting elements that may regulate changes in plastid gene expression. However, the use of tobacco as an experimental system depends on the existence of a similar response to green light. To test the response in tobacco, etiolated seedlings were treated with short single pulses of green light and psaA and psbD transcript abundance was assayed. These candidate plastid transcripts decreased in abundance within 15 min of a short, single pulse of green light. The response is induced with as few as 10¹ μmol m^-2 photons of green light. These data indicate that the response in etiolated tobacco seedlings is faster and more sensitive than it is in Arabidopsis. These findings suggest that tobacco is an appropriate surrogate for biochemical dissection of the green-light-induced plastid response. As important, the data indicate that the counterintuitive response to green wavebands persists in species distant from Arabidopsis, indicating that it is not simply a laboratory curiosity associated with a single species.