Isolation of a novel barley cDNA encoding a nuclear protein involved in stress response and leaf senescence

Abstract

In order to isolate genes involved in the early acclimation of winter barley (Hordeum vulgare L. cv. Trixi) to a combined cold and light stress of 2°C and 600 μmol m-2 s-1 restriction fragment differential display-polymerase chain reaction was performed. Impact of the cold-treatment on the leaves was characterized by measuring chlorophyll content and photosystem II efficiency. By this approach several cDNAs of genes that quickly and transiently up-regulated during early stages of the stress were identified. One of these genes (HvFP1) includes sequence motifs representing a heavy metal associated domain (HMA), nuclear localization signals (NLS) and a farnesylation motif. This gene is also induced at drought stress, during leaf senescence and after exposure to abscisic acid. Analysis of its spatial expression patterns in barley plants either grown at 21 or 2°C showed that in contrast to the situation in leaves transcript level of this gene is high not only in cold-treated plants but also in controls kept at 21°C in plant compartments enriched in meristematic tissues. The nuclear localization of the protein was confirmed by confocal laser scanning microscopy of epidermal onion cells after particle bombardment with chimeric HVFP1-GFP constructs. Using a construct with a modified farnesylation motif yielded a different pattern of nuclear distribution of the chimeric protein.