UV-B, red and far-red light regulate induction of the C4 isoform of NADP-malic enzyme in etiolated maize seedlings

Abstract

The induction of NADP-malic enzyme (NADP-ME) in maize (Zea mays) etiolated seedlings as a function of intensity and duration of exposure to UV-B radiation was investigated by measuring changes in activity and protein, as well as by levels of NADP-ME gene transcripts. Exposures to UV radiation from 2 to 60 min including photon flux densities of UV-B of 0.5–2 mmol quanta m-2 s-1 which are well below levels which occur naturally under full sunlight, caused an increase in Me gene mRNA and NADP-ME protein, as well as in NADP-ME activity. A similar dosage of UV-A radiation was ineffective. A low level of red light (10 µmol quanta m-2 s-1) for only 5 min was also effective in inducing increases in NADP-ME activity equivalent to that with UV-B radiation. A 5 min exposure to far red light (100 µmol quanta m-2 s-1) following UV-B or red light treatment largely reversed the induction of NADP-ME, and this effect of far-red could be eliminated by further treatment with UV-B or red light. These results indicate that physiological levels of UV-B radiation have a positive effect on induction of the synthesis of a photosynthetic enzyme which is involved in C4 photosynthesis.

UV‐B and UV‐C induction of NADP‐malic enzyme in tissues of different cultivars of Phaseolus vulgaris (bean)

“…We have recently shown that UV‐B radiation could induce NADP‐ME activity in both etiolated and green maize leaves (a C 4 plant) (Drincovich et al . 1998; Casati et al . 1998) and also in leaves of different cultivars of bean (a C 3 plant) (Pinto et al .…”

“…The NADP‐ME activity of etiolated maize seedlings was previously reported to be markedly increased above constitutive levels not only after exposure to PAR supplemented with UV‐B radiation but also by red light (Casati et al . 1998).…”

“…1998). Red light was shown to be as effective as UV‐B in inducing NADP‐ME in maize plants, and exposure to far‐red light immediately after UV‐B reduced the inductive effect on NADP‐ME (Casati et al . 1998).…”

“…NADP‐ME from different tissues of bean (a C 3 plant) responds to induction by UV‐B radiation in a similar way to that previously described for NADP‐ME from maize leaves (a C 4 plant) (Drincovich et al . 1998; Casati et al . 1998, 1999).…”

“…Red light was as effective as UV‐B in inducing NADP‐ME, and after a short exposure to far‐red light applied immediately after red or UV‐B light, the inductive effect on NADP‐ME was significantly reduced (Casati et al . 1998); providing evidence that UV‐B induction of NADP‐ME in maize, a C 4 plant, can be mediated through the phytochrome system, although it could also require the association of a UV‐B photoreceptor (Casati et al . 1998).…”