Characterization and expression analysis of a thaumatin-like protein PpTLP1 from ground cherry Physalis pubescens.

Ground cherry, Physalis pubescens, is mainly cultivated as a fruit worldwide and popularly used as a food supplement and traditional Chinese medicine. Plants are challenged by external environmental stress and can initiate resistance to the stress through the regulation of pathogenesis-related (PR) proteins. Among PR proteins, PR-5, a thaumatin-like protein (TLP), was identified in many plants and found to be able to enhance stress resistance. However, PR-5 in ground cherry is not characterized and its expression is yet to be understood. In this study, a PR-5 protein PpTLP1 in P. pubescens was firstly identified. Analysis of the amino acid sequences revealed that PpTLP1 was highly similar to PR-NP24 identified in tomato with a difference in only one amino acid. Expression analysis indicated that the PpTLP1 gene was highly expressed in leaf while the PpTLP1 protein was tissue-specifically accumulated in cherry exocarp. Furthermore, the down-regulation of PpTLP1 in ground cherry was induced by NaCl treatment while the up-regulation was promoted by the infection of Sclerotinia sclerotiorum and Botrytis cinerea. This study will provide a new plant resource containing a TLP in Physalis genus and a novel insight for the improvement of postharvest management of ground cherry and other Solanaceae plants.

New native Bacillus thuringiensis strains induce high insecticidal action against Culex pipiens pallens larvae and adults.

Mosquitoes of many species are key disease vectors, killing millions of people each year. Bacillus thuringiensis-based insecticide formulations are largely recognized as among the most effective, ecologically safe, and long-lasting methods of managing insect pests. New B. thuringiensis strains with high mosquito control effectiveness were isolated, identified, genetically defined, and physiologically characterized. Eight B. thuringiensis strains were identified and shown to carry endotoxin-producing genes. Using a scanning electron microscope, results revealed typical crystal forms of various shapes in B. thuringiensis strains. Fourteen cry and cyt genes were found in the strains examined. Although the genome of the B. thuringiensis A4 strain had twelve cry and cyt genes, not all of them were expressed, and only a few protein profiles were observed. The larvicidal activity of the eight B. thuringiensis strains was found to be positive (LC50: 1.4-28.5 g/ml and LC95: 15.3-130.3 g/ml). Bioassays in a laboratory environment demonstrated that preparations containing B. thuringiensis spores and crystals were particularly active to mosquito larvae and adults. These new findings show that the novel preparation containing B. thuringiensis A4 spores and crystals mixture might be used to control larval and adult mosquitoes in a sustainable and ecologically friendly manner.

Characterization of microRNA-like RNAs associated with sclerotial development in Sclerotinia sclerotiorum.

Sclerotinia sclerotiorum is a model necrotrophic pathogen causing great economic losses worldwide. Sclerotia are dormant structures that play significant biological and ecological roles in the life and disease cycles of S. sclerotiorum and other species of sclerotia-forming fungi. microRNA-like RNAs (milRNAs) as non-coding small RNAs play regulatory roles in fungal development and pathogenicity. Therefore, milRNAs associated with sclerotial development in S. sclerotiorum were investigated in this study. A total of 275 milRNAs with induced expression during sclerotia development were identified, in which 51 were differentially expressed. The target genes of all milRNAs were predicted. The putative functions of the targets regulated by milRNAs were annotated by Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses. The expression levels of six selected milRNAs that coordinated with their corresponding targets were validated by qRT-PCR. Among these six milRNAs, Ssc-milR-240 was potentially associated with sclerotial development by epigenetic regulation of its target histone acetyltransferase. This study will facilitate the better understanding of the milRNA regulation associated with sclerotial development in S. sclerotiorum and even other sclerotia-forming fungi. This work will provide novel insights into the molecular regulations of fungal morphogenesis and the candidate targets of milRNAs used for the sustainable management of plant diseases caused by S. sclerotiorum.

Molecular Characterization of the Thaumatin-like Protein PR-NP24 in Tomato Fruits.

Pathogenesis-related proteins play significant roles in plant responses to pathogen infection and environmental stresses. PR-5 proteins are thaumatin-like proteins (TLPs) and can improve plant resistance to diseases. In this study, a protein named PR-NP24 belonging to the PR-5 family was found to be specifically expressed in tomato exocarp. Subsequently, PR-NP24 and orthologous TLPs were identified in partial Solanaceae species. The differential expression patterns of the PR-NP24 protein in the exocarp of tomato were further analyzed, which resulted in a better understanding of PR-NP24 regulation in plant responses to abiotic and biotic stresses. Accumulation of PR-NP24 induced by salt (NaCl) treatment could promote plant resistance against invasive fungal pathogens. This study concluded that the regulation of PR-NP24 in tomato exocarp could possibly be applied to improve the harvest management of tomato fruits as well as be of practical significance to control the allergenic potentials of the fruits of other plants.