A role for ethylene in the phytochrome-mediated control of vegetative development

A role for ethylene in the phytochrome-mediated control of vegetative development

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Unformatted text preview: A role for ethylene in the phytochrome-mediated control of vegetative development Eloise Foo 1 , John J. Ross 1 , Noel W. Davies 2 , James B. Reid 1 and James L. Weller 1,* 1 School of Plant Science, University of Tasmania, Private Bag 55, Hobart, Tasmania 7001, Australia, and 2 Central Science Laboratory, University of Tasmania, Private Bag 74, Hobart, Tasmania 7001, Australia Received 2 November 2005; revised 23 January 2006; accepted 7 February 2006. * For correspondence (fax þ 61 362262698; e-mail jim.weller@utas.edu.au). Summary Members of the phytochrome family of photoreceptors play key roles in vegetative plant development, including the regulation of stem elongation, leaf development and chlorophyll accumulation. Hormones have been implicated in the control of these processes in de-etiolating seedlings. However, the mechanisms by which the phytochromes regulate vegetative development in more mature plants are less well understood. Pea ( Pisum sativum ) mutant plants lacking phytochromes A and B, the two phytochromes present in this species, develop severe defects later in development, including short, thick, distorted internodes and reduced leaf expansion, chlorophyll content and CAB gene transcript level. Studies presented here indicate that many of these defects in phyA phyB mutant plants appear to be due to elevated ethylene production, and suggest that an important role of the phytochromes in pea is to restrict ethylene production to a level that does not inhibit vegetative growth. Mutant phyA phyB plants produce significantly more ethylene than WT plants, and application of an ethylene biosynthesis inhibitor rescued many aspects of the phyA phyB mutant phenotype. This deregulation of ethylene production in phy-deficient plants appears likely to be due, at least in part, to the elevated transcript levels of key ethylene-biosynthesis genes. The phytochrome A photoreceptor appears to play a prominent role in the regulation of ethylene production, as phyA , but not phyB , single-mutant plants also exhibit a phenotype consistent with elevated ethylene production. Potential interactions between ethylene and secondary plant hormones in the control of the phy-deficient mutant phenotype were explored, revealing that ethylene may inhibit stem elongation in part by reducing gibberellin levels. Keywords: phytochrome, ethylene, vegetative development, Pisum , gibberellin. Introduction Light plays a central role in plant development, and the phytochrome photoreceptors are important regulators of a wide range of light responses. Phytochromes are well known for their role in seedling de-etiolation, with response to red light mediated by the phytochrome A (phyA) and phytochrome B (phyB)-type photoreceptors, and response to far-red light mediated solely by phyA (Neff et al. , 2000; Takano et al. , 2001; van Tuinen et al. , 1995; Weller et al. , 1995, 2000, 2001b; Whitelam et al. , 1993). Phytochromes also play a role in seedling establishment under blue light,...
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This note was uploaded on 08/01/2009 for the course 231 224-12 taught by Professor Mazik during the Spring '06 term at A.T. Still University.

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A role for ethylene in the phytochrome-mediated control of vegetative development

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