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Gene Review:

HEMA3 - glutamyl-tRNA reductase

Arabidopsis thaliana

Synonyms: F16D14.9, F16D14_9

Kumar, A.M. et al., McCormac, A.C. et al., Kumar, M.A. et al., Kumar, A.M. et al., McCormac, A.C. et al., et al.

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High impact information on HEMA3

To understand how this co-ordination is achieved, we have made a detailed study of the light-regulated signalling pathways mediating the expression of the HEMA1 and Lhcb genes encoding glutamyl-tRNA reductase, the first committed enzyme of 5-aminolaevulinic acid formation, and chlorophyll a/b-binding proteins, respectively [1].
The first enzyme committed to ALA synthesis is glutamyl-tRNA reductase encoded in Arabidopsis by a small family of nuclear-encoded HEMA genes [2].
In the first step, glutamyl-tRNA reductase (GluTR), converts glutamate of glutamyl-tRNA to glutamate 1-semialdehyde (GSA) which is rearranged to ALA by glutamate 1-semialdehyde-2,1-aminomutase (GSA-A) in the second step [3].
The expression of glutamyl-tRNA reductase (GluTR), the first enzyme in the pathway, was severely inhibited by NF, while treatment with this compound did not significantly reduce the levels of the other enzyme, glutamate-l-semialdehyde aminomutase, or of tRNA(Glu), the initial metabolite of the pathway [4].

Biological context of HEMA3

The deduced amino acid sequence predicts a HEMA2 protein of 530 amino acids with 79% identity to the HEMA1-encoded GluTR [3].

Associations of HEMA3 with chemical compounds

Analysis indicated that these plants had decreased levels of chlorophyll, non-covalently bound hemes, and ALA; their levels were proportional to the level of glutamyl-tRNA reductase expression and were inversely related to the levels of antisense HEMA transcripts [5].

Other interactions of HEMA3

We have examined the expression of the HEMA1 gene, which encodes the key chlorophyll synthesis enzyme glutamyl-tRNA reductase, during the phytochrome A-mediated far-red light (FR) block of greening response in Arabidopsis [6].

References

Light-signalling pathways leading to the co-ordinated expression of HEMA1 and Lhcb during chloroplast development in Arabidopsis thaliana. McCormac, A.C., Terry, M.J. Plant J. (2002) [Pubmed]
Divergent regulation of the HEMA gene family encoding glutamyl-tRNA reductase in Arabidopsis thaliana: expression of HEMA2 is regulated by sugars, but is independent of light and plastid signalling. Ujwal, M.L., McCormac, A.C., Goulding, A., Kumar, A.M., Söll, D., Terry, M.J. Plant Mol. Biol. (2002) [Pubmed]
A second and differentially expressed glutamyl-tRNA reductase gene from Arabidopsis thaliana. Kumar, A.M., Csankovszki, G., Söll, D. Plant Mol. Biol. (1996) [Pubmed]
Selective inhibition of HEMA gene expression by photooxidation in Arabidopsis thaliana. Kumar, M.A., Chaturvedi, S., Söll, D. Phytochemistry (1999) [Pubmed]
Antisense HEMA1 RNA expression inhibits heme and chlorophyll biosynthesis in arabidopsis. Kumar, A.M., Söll, D. Plant Physiol. (2000) [Pubmed]
Loss of nuclear gene expression during the phytochrome A-mediated far-red block of greening response. McCormac, A.C., Terry, M.J. Plant Physiol. (2002) [Pubmed]

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