Broad-range antagonistic rhizobacteria Pseudomonas fluorescens and Serratia plymuthica suppress Agrobacterium crown gall tumours on tomato plants.

AIM: To examine the biocontrol activity of broad-range antagonists Serratia plymuthica IC1270, Pseudomonas fluorescens Q8r1-96 and P. fluorescens B-4117 against tumourigenic strains of Agrobacterium tumefaciens and A. vitis. METHODS AND RESULTS: Under greenhouse conditions, the antagonists, applied via root soak prior to injecting Agrobacterium strains into the wounded stems, significantly suppressed tumour development on tomato seedlings. A derivative of P. fluorescens Q8r1-96 tagged with a gfp reporter, as well as P. fluorescens B-4117 and S. plymuthica IC1270 marked with rifampicin resistance, stably persisted in tomato tissues for at least 1 month. Mutants of P. fluorescens Q8r1-96 and S. plymuthica IC1270 deficient in 2,4-diacetylphloroglucinol or pyrrolnitrin production, respectively, also proficiently suppressed the tumour development, indicating that these antibiotics are not responsible for the observed biocontrol effect on crown gall disease. The volatile organic compounds (VOCs) produced by the tested P. fluorescens and S. plymuthica strains inhibited the growth of A. tumefaciens and A. vitis strains in vitro. Solid-phase microextraction-gas chromatography-mass spectrometry analysis revealed dimethyl disulfide (DMDS) as the major headspace volatile produced by S. plymuthica IC1270; it strongly suppressed Agrobacterium growth in vitro and was emitted by tomato plants treated with S. plymuthica IC1270. 1-Undecene was the main volatile emitted by the examined P. fluorescens strains, with other volatiles, including DMDS, being detected in only relatively low quantities. CONCLUSIONS: S. plymuthica IC1270, P. fluorescens B-4117 and P. fluorescens Q8r1-96 can be used as novel biocontrol agents of pathogenic Agrobacterium. VOCs, and specifically DMDS, might be involved in the suppression of oncogenicity in tomato plants. However, the role of specific volatiles in the biocontrol activity remains to be elucidated. SIGNIFICANCE AND IMPACT OF THE STUDY: The advantage of applying these antagonists lies in their multiple activities against a number of plant pathogens, including Agrobacterium.

[Investigation of properties of the thermostable protein complex obtained from the myocardium left ventricles of adult white rats].

A thermostable protein complex (TSPC) obtained from the myocardium ventricules of adult rats inhibits mitotic and transcriptional activity of cardiomyocytes. At the same time this complex is more active on early stages of the postnatal ontogenesis in rats, aged 1 and 5 days. Following its action on RNA synthesis, the TSPC reveals tissue specificity only in cells with terminal differentiation, and is determined by its nuclear membranes. We continue studies for identifying the molecular weight and chemical nature of the TSPC, and the role of its different fractions in regulation of proliferation processes. Besides, it is planned to produce antibodies against TSPC fractions with the purpose to block its inhibitory effect on myocyte regeneration in the damaged myocardium.

Possible role of endogenous growth inhibitors in regeneration of organs: searching for new approaches.

A hydrophilic protein component (12-17 kDa) of the thermostable protein complex (TSPC) of different organs (heart, liver, kidney, brain) of adult white rats has been identified using hydrophobic interaction chromatography (HIC). Chromatograms and spectra of the myocardial hydrophilic component of different animals (snail, pigeon, rat, pig) detected within the UV region (190-360 nm) have shown that in different organs of the same animal species as well as in the same organ (e.g. heart) of different species, TSPC contains identical hydrophilic components, i.e. there is clearly a phylogenetically conserved group of thermostable proteins that regulates proliferation processes.