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

Abstract

The effects of the treatment of different tissues of three bean cultivars (Pinto, Vilmorin and Arroz) with ultra-violet (UV) UV-B and UV-C radiation and red light on the activity, quantity and RNA levels of NADP-malic enzyme (NADP-ME) were determined. Exposure to UV-B radiation for 8 h caused a marked increase of NADP-ME from leaves, stems and roots in the three cultivars studied. A similar induction was observed in the leaves and stems after 8 h of exposure under UV-C, but not in the roots, suggesting that a different signal might be acting to induce the expression of NADP-ME after UV-B and UV-C exposure. In contrast, red light was ineffective in inducing NADP-ME in either tissue, so the regulation of the expression of this enzyme is phytocrome-independent. The activity of superoxide dismutase, ascorbate peroxidase, catalase and peroxidase was also different in plants treated with UV-B, UV-C and photosynthetically active radiation, suggesting that various pathways may be acting in the regulation of these enzymes by UV-B and UV-C. Reactive oxygen species (ROS) were also required for UV-B induction of NADP-ME, as the addition of ascorbic acid before UV-B treatment prevented NADP-ME induction, whereas salicylic acid was not effective in inducing the enzyme, showing that NADP-ME induction by UV-B is ROS dependent but salicylic acid independent.

Expression of an NADP-malic enzyme gene in rice (Oryza sativa. L) is induced by environmental stresses; over-expression of the gene in Arabidopsis confers salt and osmotic stress tolerance

“…In bean (Phaseolus vulgaris), the NADP-ME gene promoter is activated by different effectors (fungal elicitors, UV irradiation, and wounding) and agents producing redox perturbations (Walter et al 1994;Schaaf et al 1995). NADP-ME activity was also increased by UV-B radiation in bean (Pinto et al 1999;Casati and Andreo 2001) and in maize Drincovich et al 1998), and by NaCl stress in Aloe vera L. (Sun et al 2003). Our finding that over-expression of rice NADP-ME 2 in Arabidopsis plants increased salt and osmotic stresses tolerance (Figs.…”

A cytosolic NADP-malic enzyme gene from rice (Oryza sativa L.) confers salt tolerance in transgenic Arabidopsis

“…Total extractable NADP-ME activity was measured for 4-weekold WT seedlings and T 3 generation seedlings of seven independently transgenic lines (TP 2 , TP 5 , TP 7 , TP 9 , TP 10 , TP 11 , TP 15 ). Data represent the means (±SD) of three independent assays NADPH provides the reducing power required for reactive oxygen species metabolism (Minard and McAlister-Henn 2001;Møller 2001), and NADPH is also required for synthesis of pigments (antiantioxidant) and other cellular components involved in protection and repair processes under UV-B radiation Pinto et al 1999;Casati and Andreo 2001). The NADPH+NADP + and NADPH/NADP + ratio were analyzed in transgenic lines and WT plants.…”

Phenols, proline and low-molecular thiol levels in pea (Pisum sativum) plants respond differently toward prolonged exposure to ultraviolet-B and ultraviolet-C radiations

“…In algae, however, the effect of UV-C attracted more attention (Duval et al 2000). Recently, studies of UV-C effect on higher plants have been re-evaluated (Casati and Andreo 2001;Shama and Alderson 2005;Procházková and Wilhelmova 2007). In a review Shama and Alderson (2005) considered hormetic (beneficial) effect of low UV-C irradiation doses (0.5-9.0 kJ m -2 ) in commercial prospects to prevent pathogen disease and delay senescence during fruit storage.…”