The Elm1 (ZmHy2) gene of maize encodes a phytochromobilin synthase

Sawers, Ruairidh J.H., Linley, Philip J., Gutierrez-Marcos, Jose F., Delli-Bovi, Teegan, Farmer, Phyllis R., Kohchi, Takayuki, Terry, Matthew J. and Brutnell, Thomas P. (2004) The Elm1 (ZmHy2) gene of maize encodes a phytochromobilin synthase. Plant Physiology, 136, (1), 2771-2781. (doi:10.1104/pp.104.046417).


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The light insensitive maize (Zea mays) mutant elongated mesocotyl1 (elm1) has previously been shown to be deficient in the synthesis of the phytochrome chromophore 3E-phytochromobilin (PB). To identify the Elm1 gene, a maize homolog of the Arabidopsis PB synthase gene AtHY2 was isolated and designated ZmHy2. ZmHy2 encodes a 297-amino acid protein of 34 kD that is 50% identical to AtHY2. ZmHY2 was predicted to be plastid localized and was targeted to chloroplasts following transient expression in tobacco (Nicotiana plumbaginifolia) leaves. Molecular mapping indicated that ZmHy2 is a single copy gene in maize that is genetically linked to the Elm1 locus. Sequence analysis revealed that the ZmHy2 gene of elm1 mutants contains a single G to A transition at the 3' splice junction of intron III resulting in missplicing and premature translational termination. However, flexibility in the splicing machinery allowed a small pool of in-frame ZmHy2 transcripts to accumulate in elm1 plants. In addition, multiple ZmHy2 transcript forms accumulated in both wild-type and elm1 mutant plants. ZmHy2 splice variants were expressed in Escherichia coli and products examined for activity using a coupled apophytochrome assembly assay. Only full-length ZmHY2 (as defined by homology to AtHY2) was found to exhibit PB synthase activity. Thus, the elm1 mutant of maize is deficient in phytochrome response due to a lesion in a gene encoding phytochromobilin synthase that severely compromises the PB pool.

Item Type: Article
Digital Object Identifier (DOI): doi:10.1104/pp.104.046417
ISSNs: 0032-0889 (print)
Related URLs:
Subjects: Q Science > QK Botany
Divisions : University Structure - Pre August 2011 > School of Biological Sciences
ePrint ID: 56783
Accepted Date and Publication Date:
September 2004Published
Date Deposited: 08 Aug 2008
Last Modified: 31 Mar 2016 12:37

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