Visualization of SpoVAEa protein dynamics in dormant spores of Bacillus cereus and dynamic changes in their germinosomes and SpoVAEa during germination

Bacillus cereus spores, like most Bacillus spores, can survive for years depending on their specific structure, and germinate when their surroundings become suitable. Spore germination proteins play an important role in the initiation of germination. Because germinated spores lose the extreme resistance of the dormant state, more information related to the function of germination proteins could be useful to develop new strategies to control B. cereus spores. Prior work has shown that: i) the channel protein SpoVAEa exhibits high frequency movement in the outer leaflet of the inner membrane (IM) in dormant spores of B. subtilis; ii) the dynamics of germinosome formation in developing spores of B. cereus indicate that the formation of germinosome foci is slower than foci formation of germinant receptor GerR and scaffold protein GerD. However, the dynamics of movement of SpoVAEa in B. cereus spores, and the complete behavior of the germinosome in germinated spores of B. cereus are still unclear. In this study, we found that the SpoVAEa fluorescent foci in dormant spores of B. cereus redistribute at a lower frequency than in B. subtilis, and likely colocalize with GerD in dormant spores. Our results further indicate that: i) overexpression of GerR(A-C-B)-SGFP2 and SpoVAEa-SGFP2 with GerD-mScarlet-I from a plasmid leads to more heterogeneity and lower efficiency of spore germination in B. cereus; ii), germinosome foci composed of GerR(A-C-B)-SGFP2 and GerD-mScarlet-I were lost prior to the phase transition in germination; and iii) GerD-mScarlet-I foci spread out but continued to exist beyond the phase transition of B. cereus spores.

Extreme resistance to potato virus A in potato cultivar Barbara is independently mediated by Ra and Rysto

Potato virus A (PVA) and potato virus Y (PVY) are two common members of Potyvirus genus infecting potato crops worldwide. Host resistance offers an economical and effective means for the control and/or management of these viruses. In this study, 20 potato clones were screened for their resistance against PVA and PVY by mechanical and/or graft inoculation assay, and were explored for the relationship between extreme resistance genes Ra and Ry by the detection of molecular markers linked respectively to Ryadg, Rysto, and Rychc. Six clones, including Barbara, Jizhangshu 8, Longshu 7, Longshu 8, M6, and Solara, were found to be extremely resistant to both PVA and PVY; three clones (AC142, Eshu 3, and Shepody) were deemed to be extremely resistant to PVA but susceptible to PVY. To further reveal the inheritance of the extreme resistance (ER) against PVA, a tetraploid F1 population of Barbara × F58050 (susceptible to both PVY and PVA) and a tetraploid BC1 population of BF145 (a PVA-resistant but PVY-susceptible progeny of Barbara × F58050) × F58050 were obtained, and phenotyping of the F1 and BC1 population by graft-inoculation with PVA showed segregation ratios of 3:1 and 1:1 (R:S), respectively. These results suggested that two independent loci control ER against PVA in Barbara: one confers ER to both PVA and PVY, and the other confers ER to PVA only. The deduced genotype of Barbara is RyryryryRararara.

Pressure and Temperature Combined With Microbial Supernatant Effectively Inactivate Bacillus subtilis Spores

Spores from the Bacillus species pose a challenge to the food industry because of their ubiquitous nature and extreme resistance. Accumulated evidence indicates that it is effective to induce spore germination homogenously before killing them. However, it is difficult to obtain and apply exogenous germination factors, which will affect food composition. Therefore, this study screened endogenous germinants from microorganisms by assessing the effect of Escherichia coli, Bacillus subtilis, Saccharomyces cerevisiae, Lactiplantibacillus plantarum, and Streptococcus thermophilus cultures (cell-free) on B. subtilis spore germination. The results showed that the supernatants from these five microorganisms induced spore germination instead of sediments. Moreover, the supernatants of E. coli, B. subtilis, and S. cerevisiae exhibited higher germination rates than L. plantarum and S. thermophilus, and the induction effects were concentration-dependent. Furthermore, plate counting confirmed that the microbial supernatants induced the lowest spore germination ratio on strains B. subtilis FB85 [germination receptors (GRs) mutant] but not strains B. subtilis PB705 (PrkC mutant). In addition, B. subtilis and S. cerevisiae supernatants, combined with pressure and temperature, were effective in spore inactivation. The findings suggested that microbial supernatants may include agents that induce spore germination and may be used for spore inactivation.

Extreme Resistance to Viruses in Potato and Soybean

Plant pathogens, including viruses, negatively impact global crop production. Plants have evolved complex immune responses to pathogens. These responses are often controlled by nucleotide-binding leucine-rich repeat proteins (NLRs), which recognize intracellular, pathogen-derived proteins. Genetic resistance to plant viruses is often phenotypically characterized by programmed cell death at or near the infection site; a reaction termed the hypersensitive response. Although visualization of the hypersensitive response is often used as a hallmark of resistance, the molecular mechanisms leading to the hypersensitive response and associated cell death vary. Plants with extreme resistance to viruses rarely exhibit symptoms and have little to no detectable virus replication or spread beyond the infection site. Both extreme resistance and the hypersensitive response can be activated by the same NLR genes. In many cases, genes that normally provide an extreme resistance phenotype can be stimulated to cause a hypersensitive response by experimentally increasing cellular levels of pathogen-derived elicitor protein(s). The molecular mechanisms of extreme resistance and its relationship to the hypersensitive response are largely uncharacterized. Studies on potato and soybean cultivars that are resistant to strains of Potato virus Y (PVY), Potato virus X (PVX), and Soybean mosaic virus (SMV) indicate that abscisic acid (ABA)-mediated signaling and NLR nuclear translocation are important for the extreme resistance response. Recent research also indicates that some of the same proteins are involved in both extreme resistance and the hypersensitive response. Herein, we review and synthesize published studies on extreme resistance in potato and soybean, and describe studies in additional species, including model plant species, to highlight future research avenues that may bridge the gaps in our knowledge of plant antiviral defense mechanisms.

Gene conversion facilitates the adaptive evolution of self-resistance in highly toxic newts

Tarichanewts contain high concentrations of the deadly toxin TTX as an antipredator defense, requiring them to be physiologically resistant to their own toxin. Here, we reconstruct the origins of TTX self-resistance by sequencing the voltage-gated sodium channel (SCNA) gene family, the target of TTX, in newts and related salamanders. We show that extreme resistance in newts consists of a mixture of ancient changes and lineage-specific substitutions and that the nonsynonymous substitution rate is elevated in newts, suggesting positive selection. We also identify a novel exon duplication withinSCN4Aencoding an expressed TTX-binding site. Two resistance-conferring changes within newts appear to have spread via nonallelic gene conversion: in one case, one codon was copied between paralogs, and in the second, multiple substitutions were homogenized between the duplicate exons ofSCN4A. Our results demonstrate that gene conversion can accelerate the coordinated evolution of gene families in response to selection.

Preparation of Versatile, Porous Poly-Arylthioethers by Reversible Pd-Catalysed C–S/C–S Metathesis

Porous organic frameworks have shown a number of promising properties; however, their industrial application is usually hampered due to the lability of their linkages (imine, boroxine, etc.). Inspired by the outstanding chemical, mechanical and thermal resistance of the 1D polymer polyphenylene sulfide (PPS), we hypothesized that 2D and 3D poly-arylthioether frameworks would merge the attractive features common to porous frameworks and PPS in a single material. Herein, we report a Pd-catalysed C–S/C–S metathesis-based method to prepare new porous poly-arylthioether frameworks in good yields. The self-correcting nature of the process has enabled the synthesis of new, robust materials with high surface areas. Despite the frameworks’ extreme resistance to harsh chemicals, they can be fully recycled to recover the original building blocks using the same catalytic reaction. In addition, we demonstrate preliminary results showing that these materials have great potential in several environmentally relevant applications including metal capture, metal sensing and heterogeneous catalysis. In a broader context, these results clearly demonstrate the untapped potential of emerging single-bond metathesis reactions in the preparation of new materials.

Preparation of Versatile, Porous Poly-Arylthioethers by Reversible Pd-Catalysed C–S/C–S Metathesis

Porous organic frameworks have shown a number of promising properties; however, their industrial application is usually hampered due to the lability of their linkages (imine, boroxine, etc.). Inspired by the outstanding chemical, mechanical and thermal resistance of the 1D polymer polyphenylene sulfide (PPS), we hypothesized that 2D and 3D poly-arylthioether frameworks would merge the attractive features common to porous frameworks and PPS in a single material. Herein, we report a Pd-catalysed C–S/C–S metathesis-based method to prepare new porous poly-arylthioether frameworks in good yields. The self-correcting nature of the process has enabled the synthesis of new, robust materials with high surface areas. Despite the frameworks’ extreme resistance to harsh chemicals, they can be fully recycled to recover the original building blocks using the same catalytic reaction. In addition, we demonstrate preliminary results showing that these materials have great potential in several environmentally relevant applications including metal capture, metal sensing and heterogeneous catalysis. In a broader context, these results clearly demonstrate the untapped potential of emerging single-bond metathesis reactions in the preparation of new materials.

Reactive oxygen species contribute to symptomless, extreme resistance to Potato virus X in tobacco

Here we show that in tobacco (Nicotiana tabacum cv. Samsun NN Rx1) the development of Rx1 gene-mediated, symptomless, extreme resistance to Potato virus X (PVX) is preceded by an early, intensive accumulation of the reactive oxygen species (ROS) superoxide (O2.-), evident between 1-6 hours after inoculation and associated with enhanced NADPH oxidase activities. This suggests a direct contribution of this ROS to virus restriction during symptomless, extreme resistance. Superoxide inhibition in PVX-inoculated leaves by infiltration of antioxidants (superoxide dismutase, SOD and catalase, CAT) partially suppresses extreme resistance parallel with the appearance of localized leaf necrosis resembling a hypersensitive resistance response (HR). F1 progeny from crosses of Rx1 and ferritin-overproducer (deficient in production of the ROS OH.) tobaccos also display a suppressed extreme resistance to PVX, since significantly increased virus levels are coupled to HR, suggesting a role of the hydroxyl radical (OH.) in this symptomless antiviral defense. In addition, treatment of PVX-susceptible tobacco with a superoxide-generating agent (riboflavin/methionine) results in HR-like symptoms and reduced PVX titers. Finally, by comparing defense responses during PVX-elicited symptomless, extreme resistance and HR-type resistance elicited by Tobacco mosaic virus (TMV) we conclude that defense reactions typical of an HR (e.g. induction of cell death/ROS-regulator genes and antioxidants) are early and transient in the course of extreme resistance. Our results demonstrate the contribution of early accumulation of ROS (superoxide, OH.) in limiting PVX replication during symptomless extreme resistance and support earlier findings that virus-elicited HR represents a delayed, slower resistance response than symptomless, extreme resistance.