Journal Article

Bundle sheath proteins are more sensitive to oxidative damage than those of the mesophyll in maize leaves exposed to paraquat or low temperatures

A.H. Kingston‐Smith and C.H. Foyer

in Journal of Experimental Botany

Volume 51, issue 342, pages 123-130
Published in print January 2000 | ISSN: 0022-0957
Published online January 2000 | e-ISSN: 1460-2431 | DOI:
Bundle sheath proteins are more sensitive to oxidative damage than those of the mesophyll in maize leaves exposed to paraquat or low temperatures

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In maize leaves growth at low temperatures causes decreases in maximum catalytic activities of photosynthetic enzymes and reduced amounts of proteins, rather than effects on regulation or co‐ordination of the photosynthetic processes. To test the hypothesis that differential localization of antioxidants between the different types of photosynthetic cell in maize leaves is a major determinant of the extreme sensitivity of maize leaves to chilling damage, oxidative damage to proteins, induced by incubation of maize leaves with paraquat, has been measured and compared with the effects incurred by growth at low temperatures. While the increase in protein carbonyl groups caused by paraquat treatment was much greater than that caused by low temperature growth conditions, most carbonyl groups were detected on bundle sheath proteins in both stress conditions. With one or two exceptions proteins located in the mesophyll tissues were free of protein carbonyl groups in both situations. Paraquat treatment caused a complete loss of the psaA gene products, modified the photosystem II reaction centre polypeptide, D1, and increased the number of peptides arising from breakdown of ribulose 1,5‐bisphosphate carboxylase oxygenase (Rubisco). In contrast, growth at 15 °C increased the abundance (but not number) of Rubisco breakdown products and decreased that of the psaB gene product while the psaA gene product and PEP carboxylase were largely unaffected. Since bundle sheath proteins are more susceptible to oxidative damage than those located in the mesophyll cells, strategies for achieving a more balanced system of antioxidant defence may be effective in improving chilling tolerance in maize.

Keywords: Maize; oxidative damage; protein degradation.; CP1, chlorophyll protein; DNPH, 2,4‐dinitrophenylhydrazine; DNP‐hydrazone, 2,4‐dinitrophenylhydrazone; PEP carboxylase, phosphoenolpyruvate carboxylase; PMSF, phenylmethylsulphonylfluoride; PSI, photosystem I; PSII, photosystem II; Rubisco, ribulose 1,5 bisphosphate carboxylase/oxygenase.

Journal Article.  5023 words.  Illustrated.

Subjects: Plant Sciences and Forestry

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