Affiliation:
1. Department of Molecular Biophysics and Biochemistry (A.M.K., D.S.) and
2. Department of Molecular, Cellular and Developmental Biology (D.S.), Yale University, New Haven, Connecticut 06520–8114.
Abstract
Abstract
5-Aminolevulinic acid (ALA) is a precursor in the biosynthesis of tetrapyrroles including chlorophylls and heme. The formation of ALA involves two enzymatic steps which take place in the chloroplast in plants. The first enzyme, glutamyl-tRNA reductase, and the second enzyme, glutamate-1-semialdehyde-2,1-aminomutase, are encoded by the nuclearHEMA and GSA genes, respectively. To assess the significance of the HEMA gene for chlorophyll and heme synthesis, transgenic Arabidopsis plants that expressed antisense HEMA1 mRNA from the constitutive cauliflower mosaic virus 35S promoter were generated. These plants exhibited varying degrees of chlorophyll deficiency, ranging from patchy yellow to total yellow. 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 antisenseHEMA transcripts. Plants that lacked chlorophyll failed to survive under normal growth conditions, indicating thatHEMA gene expression is essential for growth.
Publisher
Oxford University Press (OUP)
Subject
Plant Science,Genetics,Physiology
Cited by
112 articles.
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