Cloning of peroxisomal ascorbate peroxidase gene from barley and enhanced thermotolerance by overexpressing in Arabidopsis thaliana

A full-length cDNA clone (HvAPX1) encoding a peroxisomal type ascorbate per oxidase was isolated from barley (Hordeum vulgare cv. Haruna-nijyo) leaves by differential display. The deduced amino acid sequence of the HvAPX1 gene had 75.3% homology to that from the Gossypium hirsutum glyoxysomal APX gen e and 72.1% homology to that from the Arabidopsis thaliana peroxisomal APX gene, APX3. Southern blot analysis indicated that a single-copy gene in the barley genome encoded HvAPX1. Northern blot analysis showed that the HvAPX 1 transcript increased remarkably in response to heat, salt and abscisic ac id treatment. Induction was not caused by treatment with hydrogen peroxide. The HvAPX1 gene was introduced into A. thaliana under control of the 35S R NA promoter of the cauliflower mosaic virus. The transgenic plants were sig nificantly more tolerant to heat stress as compared with the wild-type. (C) 2001 Elsevier Science B.V. All rights reserved.