Two cold inducible genes encoding lipid transfer protein LTP4 from barley show differential responses to bacterial pathogens

The barley genesHvLtp4.2 andHvLtp4.3 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 reportedLtp4 cDNA (nowLtp4.1). Southern blot analysis indicated the existence of three or moreLtp4 genes per haploid genome and showed considerable polymorphism among barley cultivars. We have investigated the transient expression of genesHvLtp4.2 andHvLtp4.3 following transformation by particle bombardment, using promoter fusions to the-glucuronidase reporter sequence. In leaves, activities of the two promoters were of the same order as those of the sucrose synthase (Ss1) and cauliflower mosaic virus 35S promoters used as controls. Their expression patterns were similar, except thatLtp4.2 was more active thanLtp4.3 in endosperm, andLtp4.3 was active in roots, whileLtp4.2 was not. The promoters of both genes were induced by low temperature, both in winter and spring barley cultivars. Northern blot analysis, using theLtp4-specific probe, indicated thatXanthomonas campestris pv.translucens induced an increase over basal levels ofLtp4 mRNA, whilePseudomonas syringae pv.japonica caused a decrease. TheLtp4.3-Gus promoter fusion also responded in opposite ways to these two compatible bacterial pathogens, whereas theLtp4.2-Gus construction did not respond to infectio

Over-expression of phenol-oxidising peroxidases alters the UV-susceptibility of transgenic Nicotiana tabacum

* Class III peroxidases catalyse the oxidative crosslinking of UV-absorbing phenolics. The effect of changes in the activity of phenol oxidising peroxidases (EC 1.11.1.7) on UV-tolerance in Nicotiana tabacum plants has been determined. * The UV-sensitivity of transgenic N. tabacum lines, altered in their peroxidase expression pattern, was studied by measuring radiation effects on photosynthetic efficiency. * Analysis of the effect of UV-radiation on the relative variable chlorophyll fluorescence showed that the SPI-2 line, which over-expresses a defence-related cationic peroxidase, is markedly UV-tolerant. By contrast, the ROPN3-line, which overexpresses a synthetic horseradish peroxidase-C gene, was found to be UV-sensitive. The increased activity of indole-3-acetic acid (IAA) inducible peroxidases in homozygous IAA-overproducing transgenic plants was also found to correlate with UV-sensitivity. * It is concluded that only specific peroxidase isozymes, through their effects on phenolic metabolism, contribute to the UV protection response. Thus, the analysis of the role of isozymes in UV-protection addresses fundamental questions of isozyme diversity and/or redundancy in relation to phenolic substrate