SummaryEutypine, 4-hydroxy-3-(3-methyl-3-butene-1-ynyl) benzyl aldehyde, is a toxin produced by Eutypa lata, the causal agent of eutypa dieback of grapevines. It has previously been demonstrated that tolerance of some cultivars to this disease was correlated with their capacity to convert eutypine to the corresponding alcohol, eutypinol, which lacks phytotoxicity. We have thus purified to homogeneity a protein from Vigna radiata that exhibited eutypinereducing activity and have isolated the corresponding cDNA. This encodes an NADPH-dependent reductase of 36 kDa that we have named Vigna radiata eutypine-reducing enzyme (VR-ERE), based on the capacity of a recombinant form of the protein to reduce eutypine into eutypinol. The strongest homologies (86.8%) of VR-ERE at the amino acid level were found with CPRD14, a drought-inducible gene of unknown function, isolated from Vigna unguiculata and with an aromatic alcohol dehydrogenase (71.7%) from Eucalyptus gunnii. Biochemical characterization of VR-ERE revealed that a variety of compounds containing an aldehyde group can act as substrates. However, the highest affinity was observed with 3-substituted benzaldehydes. Expression of a VR-ERE transgene in Vitis vinifera cells cultured in vitro conferred resistance to the toxin. This discovery opens up new biotechnological approaches for the generation of grapevines resistant to eutypa dieback.

A 36‐kDa 1‐aminocyclopropane‐1‐carboxylate (ACC) N‐malonyltransferase, which converts the ethylene precursor ACC into the conjugated derivative malonyl‐ACC (MACC), has been isolated from etiolated mung bean (Vigna radiata) hypocotyls, and partially purified in a four‐step procedure. The enzyme is stimulated about 7‐fold by 100 mM K+ salts or 0.5 mM Co2+ salts, and is inhibited competitively by D‐phenylalanine (Ki= 1.3 mM) and non competitively by CoASH (0.3 mM). Beside malonyl‐CoA, it is capable to use succinyl‐CoA as an acyl donor. The 36‐kDa enzyme described here exhibits a lower optimum temperature (40°C) and a 7‐ or 3‐fold lower apparent Km for ACC (68 μM) and malonyl‐CoA (74 μM), respectively, when compared with its 55 kDa isoform already isolated from the same plant material. This data support the idea that several isoforms of ACC N‐malonyltransferase exist in plants. These isoforms may play a differential role in regulating the availability of ACC, and consequently the rate of ethylene production, as well as detoxifying cells from D‐amino acids.

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