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Light regulation of tetrapyrrole biosynthesis in Arabidopsis

Light regulation of tetrapyrrole biosynthesis in Arabidopsis
Light regulation of tetrapyrrole biosynthesis in Arabidopsis
The tetrapyrrole biosynthesis pathway results in the synthesis of both haem and chlorophyll and tight regulation of this pathway during de-etiolation is critical for the safe biogenesis of the photosynthetic apparatus. While much attention has been paid to light regulation of the total flux through this pathway less is known about the role of light in regulating the key, metal-insertion branchpoint leading either to haem or chlorophyll. Magnesium chelatase, responsible for channelling substrates into the chlorophyll branch, is composed of three subunits (CHLD, CHLH and CHLI), with a regulatory protein, GUN4, also necessary for full enzyme activity. To understand how light affects branchpoint regulation we have studied the transcriptional regulation of the four genes encoding these proteins in de-etiolating Arabidopsis thaliana seedlings using quantitative PCR. Analysis of gene expression in dark-grown seedlings transferred to far-red and red light has shown that CHLH and GUN4 are strongly induced, while the CHLD and CHLI1 genes show little change in expression. Comparison of expression profiles in wild-type and photoreceptor-deficient mutant of Arabidopsis indicate that regulation is primarily under the control of phytochromes A and B. These results suggest that phytochrome-mediated induction of GUN4 and CHLH is a major mechanism for redirecting tetrapyrrole synthesis to the chlorophyll branch of the pathway during de-etiolation. We are now looking to test this hypothesis further by examining protein levels and the flux of tetrapyrrole intermediates through the branch point at this critical stage of plant development.
1095-6433
p.S233
Stephenson, P.
96e29517-6897-4e82-93bf-89824af52a0a
Connor, D.
0f9b0290-24f9-406f-961e-724f5de4a0fe
Terry, M.
a8c2cd6b-8d35-4053-8d77-3841c2427c3b
Stephenson, P.
96e29517-6897-4e82-93bf-89824af52a0a
Connor, D.
0f9b0290-24f9-406f-961e-724f5de4a0fe
Terry, M.
a8c2cd6b-8d35-4053-8d77-3841c2427c3b

Stephenson, P., Connor, D. and Terry, M. (2007) Light regulation of tetrapyrrole biosynthesis in Arabidopsis. Comparative Biochemistry and Physiology. Part A: Molecular & Integrative Physiology, 146 (4, Supplement 1), p.S233. (doi:10.1016/j.cbpa.2007.01.519).

Record type: Meeting abstract

Abstract

The tetrapyrrole biosynthesis pathway results in the synthesis of both haem and chlorophyll and tight regulation of this pathway during de-etiolation is critical for the safe biogenesis of the photosynthetic apparatus. While much attention has been paid to light regulation of the total flux through this pathway less is known about the role of light in regulating the key, metal-insertion branchpoint leading either to haem or chlorophyll. Magnesium chelatase, responsible for channelling substrates into the chlorophyll branch, is composed of three subunits (CHLD, CHLH and CHLI), with a regulatory protein, GUN4, also necessary for full enzyme activity. To understand how light affects branchpoint regulation we have studied the transcriptional regulation of the four genes encoding these proteins in de-etiolating Arabidopsis thaliana seedlings using quantitative PCR. Analysis of gene expression in dark-grown seedlings transferred to far-red and red light has shown that CHLH and GUN4 are strongly induced, while the CHLD and CHLI1 genes show little change in expression. Comparison of expression profiles in wild-type and photoreceptor-deficient mutant of Arabidopsis indicate that regulation is primarily under the control of phytochromes A and B. These results suggest that phytochrome-mediated induction of GUN4 and CHLH is a major mechanism for redirecting tetrapyrrole synthesis to the chlorophyll branch of the pathway during de-etiolation. We are now looking to test this hypothesis further by examining protein levels and the flux of tetrapyrrole intermediates through the branch point at this critical stage of plant development.

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More information

Published date: 1 April 2007
Additional Information: P2.27

Identifiers

Local EPrints ID: 55900
URI: http://eprints.soton.ac.uk/id/eprint/55900
ISSN: 1095-6433
PURE UUID: 21d27697-3757-4063-a212-d6ee3dd80312
ORCID for M. Terry: ORCID iD orcid.org/0000-0001-5002-2708

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Date deposited: 06 Aug 2008
Last modified: 16 Mar 2024 02:52

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Contributors

Author: P. Stephenson
Author: D. Connor
Author: M. Terry ORCID iD

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