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High Glycolate Oxidase Activity Is Required for Survival of Maize in Normal Air
Israel Zelitch, Neil P. Schultes, Richard B. Peterson, Patrick Brown and Thomas P. Brutnell
Vol. 149, No. 1 (Jan., 2009), pp. 195-204
Published by: American Society of Plant Biologists (ASPB)
Stable URL: http://www.jstor.org/stable/25594925
Page Count: 10
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A mutant in the maize (Zea mays) Glycolate Oxidase1 (GO1) gene was characterized to investigate the role of photorespiration in C₄ photosynthesis. An Activator-induced allele of GO1 conditioned a seedling lethal phenotype when homozygous and had 5% to 10% of wild-type GO activity. Growth of seedlings in high CO₂ (1%-5%) was sufficient to rescue the mutant phenotype. Upon transfer to normal air, the go1 mutant became necrotic within 7 d and plants died within 15 d. Providing [1-¹⁴C]glycolate to leaf tissue of go1 mutants in darkness confirmed that the substrate is inefficiently converted to ¹⁴CO₂, but both wild-type and GO-deficient mutant seedlings metabolized [1-¹⁴C]glycine similarly to produce [¹⁴C]serine and ¹⁴CO₂ in a 1:1 ratio, suggesting that the photorespiratory pathway is otherwise normal in the mutant. The net CO₂ assimilation rate in wild-type leaves was only slightly inhibited in 50% O₂ in high light but decreased rapidly and linearly with time in leaves with low GO. When go1 mutants were shifted from high CO₂ to air in light, they accumulated glycolate linearly for 6 h to levels 7-fold higher than wild type and 11-fold higher after 25 h. These studies show that C₄ photosynthesis in maize is dependent on photorespiration throughout seedling development and support the view that the carbon oxidation pathway evolved to prevent accumulation of toxic glycolate.
Plant Physiology © 2009 American Society of Plant Biologists (ASPB)