Structural and functional analysis of miraculin-like protein from Vitis vinifera

StMLP1, as a Kunitz trypsin inhibitor, enhances potato resistance and specifically expresses in vascular bundles during Ralstonia solanacearum infection

Miraculin-like proteins (MLPs), members of the Kunitz trypsin inhibitor (KTI) family that are present in various plants, have been discovered to have a role in defending plants against pathogens. In this study, we identified a gene StMLP1 in potato that belongs to the KTI family. We found that the expression of StMLP1 gradually increases during Ralstonia solanacearum (R. solanacearum) infection. We characterized the promoter of StMLP1 as an inducible promoter that can be triggered by R. solanacearum and as a tissue-specific promoter with specificity for vascular bundle expression. Our findings demonstrate that StMLP1 exhibits trypsin inhibitor activity, and that its signal peptide is essential for proper localization and function. Overexpression of StMLP1 in potato can enhance the resistance to R. solanacearum. Inhibiting the expression of StMLP1 during infection accelerated the infection by R. solanacearum to a certain extent. In addition, the RNA-seq results of the overexpression-StMLP1 lines indicated that StMLP1 was involved in potato immunity. All these findings in our study reveal that StMLP1 functions as a positive regulator that is induced and specifically expressed in vascular bundles in response to R. solanacearum infection.

The Chromosome-Level Genome of Miracle Fruit (Synsepalum dulcificum) Provides New Insights Into the Evolution and Function of Miraculin

Miracle fruit (Synsepalum dulcificum) is a rare valuable tropical plant famous for a miraculous sweetening glycoprotein, miraculin, which can modify sour flavors to sweet flavors tasted by humans. Here, we present a chromosome-level high-quality genome of S. dulcificum with an assembly genome size of ∼550 Mb, contig N50 of ∼14.14 Mb, and 37,911 annotated protein-coding genes. Phylogenetic analysis revealed that S. dulcificum was most closely related to Camellia sinensis and Diospyros oleifera, and that S. dulcificum diverged from the Diospyros genus ∼75.8 million years ago (MYA), and that C. sinensis diverged from Synsepalum ∼63.5 MYA. Ks assessment and collinearity analysis with S. dulcificum and other species suggested that a whole-genome duplication (WGD) event occurred in S. dulcificum and that there was good collinearity between S. dulcificum and Vitis vinifera. On the other hand, transcriptome and metabolism analysis with six tissues containing three developmental stages of fleshes and seeds of miracle fruit revealed that Gene Ontology (GO) terms and metabolic pathways of "cellular response to chitin," "plant-pathogen interaction," and "plant hormone signal transduction" were significantly enriched during fruit development. Interestingly, the expression of miraculin (Chr10G0299340) progressively increased from vegetative organs to reproductive organs and reached an incredible level in mature fruit flesh, with an fragments per kilobase of transcript per million (FPKM) value of ∼113,515, which was the most highly expressed gene among all detected genes. Combining the unique signal peptide and the presence of the histidine-30 residue together composed the main potential factors impacting miraculin's unique properties in S. dulcificum. Furthermore, integrated analysis of weighted gene coexpression network analysis (WGCNA), enrichment and metabolite correlation suggested that miraculin plays potential roles in regulating plant growth, seed germination and maturation, resisting pathogen infection, and environmental pressure. In summary, valuable genomic, transcriptomic, and metabolic resources provided in this study will promote the utilization of S. dulcificum and in-depth research on species in the Sapotaceae family.

Proteomic Analysis of Potato Responding to the Invasion of Ralstonia solanacearum UW551 and Its Type III Secretion System Mutant

The infection of potato with Ralstonia solanacearum UW551 gives rise to bacterial wilt disease via colonization of roots. The type III secretion system (T3SS) is a determinant factor for the pathogenicity of R. solanacearum. To fully understand perturbations in potato by R. solanacearum type III effectors(T3Es), we used proteomics to measure differences in potato root protein abundance after inoculation with R. solanacearum UW551 and the T3SS mutant (UW551△HrcV). We identified 21 differentially accumulated proteins. Compared with inoculation with UW551△HrcV, 10 proteins showed significantly lower abundance in potato roots after inoculation with UW551, indicating that those proteins were significantly downregulated by T3Es during the invasion. To identify their functions in immunity, we silenced those genes in Nicotiana benthamiana and tested the resistance of the silenced plants to the pathogen. Results showed that miraculin, HBP2, and TOM20 contribute to immunity to R. solanacearum. In contrast, PP1 contributes to susceptibility. Notably, none of four downregulated proteins (HBP2, PP1, HSP22, and TOM20) were downregulated at the transcriptional level, suggesting that they were significantly downregulated at the posttranscriptional level. We further coexpressed those four proteins with 33 core T3Es. To our surprise, multiple effectors were able to significantly decrease the studied protein abundances. In conclusion, our data showed that T3Es of R. solanacearum could subvert potato root immune-related proteins in a redundant manner.[Formula: see text] Copyright © 2021 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license.

Nutritional benefits, phytochemical constituents, ethnomedicinal uses and biological properties of Miracle fruit plant (Synsepalum dulcificum Shumach. & Thonn. Daniell)

Miracle fruit plant or Miracle berry plant (Synsepalum dulcificum) is a peculiar medicinal plant because of the unique taste-modifying property of its fruit which is due to the presence of the glycoprotein, miraculin. This property has been known for centuries to the people of tropical Western and Central Africa who also employ different parts of the plant in the management of various ailments. Scientific investigations have unravelled several pharmacological properties of the plant which include antidiabetic, blood cholesterol-lowering, anti-hyperuricaemia, antioxidant, anticonvulsant and anticancer properties. Also, subacute administration of the plant extract up to 200 mg/kg was not found to be toxic in rats. Apart from miraculin, other pharmacologically active compounds have been identified in the plant including alkaloids (dihydro-feruloyl-5-methoxytyramine, N-cis-caffeoyltyramine, N-cis-feruloyl-tyramine), lignins (+-syringaresinol, +-epi-syringaresinol), phytosterols, triterpenoids, phenolic acids, flavonoids, and amino acids. The plant has also been credited with notable nutritional benefits. Proper documentation of available information on folkloric use, biological activity, constituent phytocompounds, and nutritional benefits of ethnobotanicals will go a long way in affording optimal benefits from their therapeutic potentials. This can also aid in the conservation of species at risk of extinction. This work presents an up-to-date review of the ethnobotany, phytochemistry, biological and nutritional properties of Synsepalum dulcificum.