Light stimulated activity of nitrate reductase in apple roots

The nitrate reductase activity in the roots of apples grownin the dark for 48 hr prior to assay ws lower than the grownunder normal conditions of alternating 12 hr light and 12 hrdarkness. Removal of leaves, cincturing the stem, and applicationof a photosynthetic inhibitor also lowered reductase activityin the light. (Received July 9, 1973; )     

Induced Resistance to the Designer Proline-rich Antimicrobial Peptide A3-APO does not Involve Changes in the Intracellular Target DnaK

The designer proline-rich antimicrobial peptide A3-APO and its Chex1-Arg20 single chain in vivo metabolite were studied for their ability to induce bacterial resistance upon repeated incubation of Escherichia coli and Klebsiella pneumoniae strains in sublethal concentrations. While no resistant E. coli phenotype emerged to either peptides, after 10 passages the K. pneumoniae strain became resistant to the monomer but not the dimer. The major microbiological difference between A3-APO and Chex1-Arg20 is the improved membrane-disintegrating ability of the dimeric prodrug. Thus, in agreement with earlier studies, the induced resistance likely resides in some membrane component rather than the intracellular target protein DnaK. In support, no genetic alteration in the DnaK multihelical lid region could be observed in any of the sensitive or resistant bacterial strains.     

Distribution of acid proteinase activity in wheat seedlings

Acid proteinase activity in extracts from leaves of wheat seedlingswas studied by using haemoglobin as a substrate. Optimum conditionsfor extraction and assay of the enzyme(s) were developed andthese methods used to study the distribution of acid proteolyticactivity in various tissues. The effect of leaf age and senescenceon the level of activity was also investigated and the significanceof these results discussed. (Received July 14, 1975; )