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UV‐B induction of NADP‐malic enzyme in etiolated and green maize seedlings
Author(s) -
Drincovich M. F.,
Casati P.,
Andreo C. S.,
Donahue R.,
Edwards G. E.
Publication year - 1998
Publication title -
plant, cell and environment
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.646
H-Index - 200
eISSN - 1365-3040
pISSN - 0140-7791
DOI - 10.1046/j.1365-3040.1998.00240.x
Subject(s) - etiolation , malic enzyme , enzyme , horticulture , botany , chemistry , biology , agronomy , biochemistry , dehydrogenase
The effect of treatment of etiolated maize seedlings with UV‐B and UV‐A radiation, and different levels of photosynthetically active radiation (PAR, 400–700 nm), on the activity and quantity of NADP‐malic enzyme (NADP‐ME) and on RNA levels was determined. Under low levels of PAR (14 μ mol m –2 s –1 ), exposure to UV‐B radiation (9 μ mol m –2 s –1 ) but not UV‐A radiation (11 μ mol m –2 s –1 ) for 6–24 h caused a marked increase in the activity of the enzyme similar to that observed under high PAR (300 μ mol m –2 s –1 ) in the absence of UV‐B. Western blot analysis indicated there was a specific increase of the photosynthetically active isoform of the enzyme. This increase was also measured at the RNA level by dot blot analysis, indicating that the induction is displayed at the level of NADP‐ME transcription. UV‐B treatment of green leaves after a 12 h dark period also caused an increase in the activity and level of NADP‐ME. The UV‐B induction of NADP‐ME synthesis may reflect a mechanism for induction of photosynthetic processes in C 4 photosynthesis. Alternatively, the relatively low intensity of UV‐B radiation present under full sunlight might provide a signal that facilitates repair of UV‐B‐induced damage through the increased activity of different enzymes such as NADP‐ME. It is speculated that the reducing power and pyruvate generated by activity of NADP‐ME may be used for respiration in cellular repair processes and as substrates for the fatty acid synthesis required for membrane repair.