2 COLD INDUCIBLE GENES ENCODING LIPID TRANSFER PROTEIN LTP4 FROM BARLEY SHOW DIFFERENTIAL RESPONSES TO BACTERIAL PATHOGENS

The barley genes HvLtp4.2 and HvLtp4.3 both encode the lipid transfer protein LTP4 and are less than 1 kb apart in tail-to-tail orientation. They differ in their non-coding regions from each other and from the gene corresponding to a previously reported Ltp4 cDNA (now Ltp4.1). So uthern blot analysis indicated the existence of three or more Ltp4 gen es per haploid genome and showed considerable polymorphism among barle y cultivars. We have investigated the transient expression of genes Hv Ltp4.2 and HvLtp4.3 following transformation by particle bombardment, using promoter fusions to the beta-glucuronidase reporter sequence. In leaves, activities of the two promoters were of the same order as tho se of the sucrose synthase (Ss1) and cauliflower mosaic virus 35S prom oters used as controls. Their expression patterns were similar, except that Ltp4.2 was more active than Ltp4.3 in endosperm, and Ltp4.3 was active in roots, while Ltp4.2 was not. The promoters of both genes wer e induced by low temperature, both in winter and spring barley cultiva rs. Northern blot analysis, using the Ltp4-specific probe, indicated t hat Xanthomonas campestris pv. translucens induced an increase over ba sal levels of Ltp4 mRNA, while Pseudomonas syringae pv. japonica cause d a decrease. The Ltp4.3-Gus promoter fusion also responded in opposit e ways to these two compatible bacterial pathogens, whereas the Ltp4.2 -Gus construction did not respond to infection.