Accumulation of lipid peroxide-derived, toxic .ALPHA.,.BETA.-unsaturated aldehydes (E)-2-pentenal, acrolein and (E)-2-hexenal in leaves under photoinhibitory illumination

Abstract

Lipid peroxide (LOOH)-derived aldehydes and ketones (hereafter collectively designated as carbonyls) are recently recognized as cell signals and toxic species in plant stress responses. Carbonyls at low concentrations can induce stress defense genes (Sattler et al. 2006; Weber et al. 2004), while at high concentrations, they can cause damages to cell components (O'Brien et al. 2005). Recent studies have shown that enhanced detoxification of carbonyls in transgenic plants improved their tolerance to various environmental stresses, as follows: Aldehyde reductase from Medicago sativa (alfalfa) overexpressed in Nicotiana tabacum (tobacco) improved tolerance to drought stress (Oberschall et al. 2000), methyl viologen and UV-B (Hideg et al. 2003). Aldehyde dehydrogenase isozymes from Arabidopsis thaliana improved the tolerance of transgenic A. thaliana plants to NaCl, heavy metals, methyl viologen, and H 2 O 2 (Sunkar et al. 2003). Vice versa, the dehydrogenaseknockout mutants were more sensitive to dehydration and salt than wild type (Kotchoni et al. 2006). The observed correlation between the extent of damages and the content of aldehydes, as thiobarbituric acid-reactive substances, in these studies strongly supports that aldehydes are causes of stress-induced damages in vivo. It is known that a great variety of carbonyls are produced from LOOH (Grosch 1987; Kawai et al. 2007) and many of them occur in plant tissues (Schauenstein et al. 1977), but it has been scarcely investigated what carbonyl species are involved in stress-induced damage of plant cells. Among LOOH-derived carbonyls, a,b-unsaturated aldehydes (2-alkenals) have potent cytotoxicity due to their high electrophilicity to form adducts with thiols, amines, and imidazoles in proteins and with nucleotide bases (Esterbauer et al. 1991). To photosynthesis, 2alkenals showed greater toxicity than saturated aldehydes in vitro (Mano et al. 2009). In A. thaliana, we found a novel enzyme, 2-alkenal reductase (AER), to detoxify 2alkenals (Mano et al. 2002). We have made transgenic tobaccos that overexpressed the AER gene At5g16970.

Overproduction of a rice aldo–keto reductase increases oxidative and heat stress tolerance by malondialdehyde and methylglyoxal detoxification

“…Recently, inactivation of certain Calvin cycle enzymes by reactive aldehydes is reported (Mano et al 2009 (Mano et al 2009) is not accepted as susbstrate by the OsAKR1 enzyme. However, we can not exclude the possibility that other lipid peroxidederived toxic aldehydes, endogenously produced in leaves under stress (Mano et al 2010), are not substrates of OsAKR1.…”

Reactive oxygen species and reactive carbonyl species constitute a feed‐forward loop in auxin signaling for lateral root formation

“…In plants, RCS and non‐RCS oxylipin carbonyls are formed constitutively in leaves and roots, and their levels are increased in response to various stress treatments such as exposure of leaves to high light (Mano et al ., ) and methyl viologen (Yamauchi et al ., ), exposure of roots to aluminum ions (Yin et al ., ), exposure of plants to high temperature (Kai et al ., ) and NaCl (Mano et al ., ) and exposure of cultured cells to H 2 O 2 (Winger et al ., ; Biswas and Mano, ). Exogenously added RCS can induce a group of genes related to pathogen defense (Bate and Rothstein, ; Kishimoto et al ., ), cell cycle regulation (Alméras et al ., ) and the heat‐shock response (Yamauchi et al ., ).…”

NADPH-dependent Reductases Involved in the Detoxification of Reactive Carbonyls in Plants

“…Acrolein (prop-2-enal, propenal) is the simplest compound having both an ␣,␤-unsaturated bond and an aldehyde group, and it has the highest cytotoxicity among the ␣,␤-unsaturated carbonyls (2,7). It is potentially toxic to the process of photosynthesis because it strongly inhibits both thylakoid and stromal reactions (5,6); moreover, acrolein levels in tobacco leaves increased under photoinhibitory illumination (12). Thus, the elimination of acrolein generated through lipid peroxidation is necessary to maintain photosynthetic activity under stressed conditions.…”