A bioassay using Phytophthora infestam was developed to determine whether inhibitory proteins are induced in pathogen-inoculated plants. Using this bioassay, AP24, a 24-kilodalton protein causing lysis of sporangia and growth inhibition of P. infestam, was purified from tobacco plants inoculated with tobacco mosaic virus. Analysis of the N-terminal amino acid sequence identified AP24 as the thaumatin-like protein osmotin II. The sequence was also similar to NP24, the salt-induced protein from tomato. Subsequently, we purified a protein from tomato plants inoculated with P. infestam that had inhibitory activities identical to those of the tobacco AP24. The N-terminal amino acid sequence of this protein was also similar to those of osmotin and NP24. In general, both the tobacco and tomato AP24 caused lysis of sporangia at concentrations greater than 40 nanomolar and severely inhibited hyphal growth at concentrations greater than 400 nanomolar. Because both proteins were induced by pathogen inoculation, we discussed the possible involvement of these proteins as a plant defense mechanism.

Escherichia coli minicells harboring plasmid CloDF13 synthesized at least 25 messenger ribonucleic acid (RNA) species; three of these RNAs, a 2,400-, a 2,200-, and a 100-nucleotide RNA, were synthesized in relatively large amounts. Using insertion and deletion mutants of CloDF13 as well as an RNA blotting technique, we could demonstrate that these three RNAs are transcripts from the CloDF13 DNA region from 0 to 40%. This region contains the cloacin and immunity genes and the genetic information involved in plasmid DNA replication. A transcription map of this region is presented and discussed. The data indicate that the cloacin and immunity genes were coordinately transcribed into messenger RNAs of about 2,400 and 2,200 nucleotides, which differ in length at their 3' terminus. RNA polymerase binding studies and in vitro transcription assays indicated that transcription of these genes initiates at a promoter located around 32% on the CloDF13 map. Furthermore, it is shown that a 100-nucleotide RNA is encoded by the CloDF13 DNA region between 7.7 and 8.8% on the plasmid genome; the synthesis of this RNA proceeds in a direction opposite to the transcription of the cloacin and immunity genes.tively labeled DNA. Our results indicate that 579 on August 5, 2020 by guest