Lipid transfer protein genes specifically expressed in barley leaves and coleoptiles

Genes/cDNAs encoding so-called lipid-transfer proteins (LTPs) have been isolated from a variety of tissues from different plants, but the in-vivo function of the LTP proteins is not yet known. In barley (Hordeum vulgare L.), the LTP1 gene (encoding a probable amylase/protease inhibitor, Mundy and Rogers 1986, Planta 169, 51-63) is active in aleurone tissue, and in this paper two LTP-encoding cDNAs isolated from green leaves are described. The encoded proteins start with signal sequences, they are 75% homologous to each other, 60-63% homologous to rice aleurone LTP and maize seed/coleoptile LTP, but only 48% homologous to barley aleurone LTP. Northern hybridization experiments established that the two seedling-specific genes are both highly expressed in leaves and coleoptiles whereas the LTP1 gene is inactive in seedlings. No LTP gene expression was detected in roots using either seedling or aleurone cDNA clones as probes. Tissue-print hybridization indicates that the LTP genes are first expressed in young epidermal cells in leaves and coleoptiles, and subsequently expressed in the vascular strands. Genomic Southern analysis indicates that the barley LTP gene family has four to six members.