Developmental and pathogen-induced expression of three barley genes encoding lipid transfer proteins

Clones for three barley non-specific lipid transfer proteins (LTP2, LTP3, and LTP4; formerly Cw18, Cw20 and Cw21, respectively) which had been previously shown to inhibit growth of plant pathogens, were selected and characterized from a cDNA library derived from young etiolated leaves. Genes Ltp2 and Ltp4 were located in chromosome 3H and gene Ltp3 was assigned to chromosome 7H by Southern blot analysis of wheat-barley disomic addition lines, using gene-specific probes (3'-ends of cDNAs). These assignments were confirmed by the polymerase chain reaction, using specific primers. The three genes were expressed in stem, shoot apex, leaves and roots (at low levels) throughout development. Genes Ltp3 and Ltp4 were expressed at high levels, and Lpt2 at low levels, in the spike (rachis, lemma plus palea and grain coats). Neither of the mRNAs was detected in endosperm. The proteins were localized by tissue-printing with polyclonal antibodies in the outer cell layer of the exposed surfaces of the plant, throughout the embryo, and in vascular tissues. Expression levels in leaves were moderately increased by 0.34 M NaCl and by 0.1 mM abscisic acid and were not affected by cold, drought, salicylate, 2,6-dichloro-isonicotinic acid, ethylene or ethephon. Methyl Jasmonate (10 microM) switched off all three genes. Inoculation with Av6 or vir6 isolates of the fungal pathogen Erysiphe graminis increased the three mRNAs, especially that of LTP4, which reached a maximum nine-fold increase 12-16 h after infection.