No abstract

Solanum sisymbriifolium is a critical wild eggplant resource with resistance to many serious diseases that affect eggplant production. In this study, the chloroplast genome of S. sisymbriifolium was successfully sequenced using Illumina high-throughput sequencing technology. The length of the complete chloroplast genome is 155,771 bp, and its GC content is 37.76%. There is a large single-copy region (86,404 bp), a small single-copy region (18,525 bp), and a pair of inverted repeat regions (25,421 bp) in the chloroplast genome. A total of 128 coding genes were annotated in the entire chloroplast genome, including 83 protein-coding genes, 37 transfer RNA genes and eight ribosomal RNA genes. The phylogenetic tree of 17 complete chloroplast genomes shows that S. sisymbriifolium is closely related to Solanum wrightii .

Eggplant verticillium wilt, caused by Verticillium spp., is a severe eggplant vascular disease. Solanum sisymbriifolium, a wild species of eggplant that is resistant to verticillium wilt, will be beneficial for genetically modifying eggplants. To better reveal the response of wild eggplant to verticillium wilt, proteomic analysis by iTRAQ technique was performed on roots of S. sisymbriifolium after exposure to Verticillium dahliae, and some selected proteins were also validated using parallel reaction monitoring (PRM). After inoculation with V. dahliae, the phenylalanine ammonia lyase (PAL) and superoxide dismutase (SOD) enzymes and the malondialdehyde (MDA) and soluble protein (SP) of S. sisymbriifolium roots all exhibited an increase in activity or content compared with that of the mock-inoculated plants, especially at 12 and 24 h post-inoculation (hpi). A total of 4890 proteins (47.04% of the proteins were from S. tuberosum and 25.56% were from S. lycopersicum according to the species annotation) were identified through iTRAQ and LC-MS/MS analysis. A total of 369 differentially expressed proteins (DEPs) (195 downregulated and 174 upregulated) were obtained by comparison of the control and treatment groups at 12 hpi, and 550 DEPs (466 downregulated and 84 upregulated) were obtained by comparison of the groups at 24 hpi. The most significant Gene Ontology (GO) enrichment terms at 12 hpi were regulation of translational initiation, oxidation-reduction, and single-organism metabolic process in the biological process group; cytoplasm and eukaryotic preinitiation complex in the cellular component group; and catalytic activity, oxidoreductase activity, and protein binding in the molecular function group. Small molecule metabolic, organophosphate metabolic, and coenzyme metabolic processes in the biological process group; the cytoplasm in the cellular component group; and catalytic activity and GTPase binding in the molecular function group were significant at 24 hpi. Then, KEGG (Kyoto Encyclopedia of Genes and Genomes) analysis was performed, and 82 and 99 pathways (15 and 17, p-value < 0.05) were found to be enriched at 12 and 24 hpi, respectively. Selenocompound metabolism, ubiquinone, and other terpenoid-quinone biosyntheses, fatty acid biosynthesis, lysine biosynthesis, and the citrate cycle were the top five significant pathways at 12 hpi. Glycolysis/gluconeogenesis, biosynthesis of secondary metabolites, linoleic acid metabolism, pyruvate metabolism, and cyanoamino acid metabolism were the top five at 24 hpi. Some V. dahliae-resistance-related proteins, including phenylpropanoid-pathway-related proteins, stress and defense response proteins, plant–pathogen interaction pathway and pathogenesis-related proteins, cell wall organization and reinforcement-related proteins, phytohormones-signal-pathways-related proteins, and other defense-related proteins were identified. In conclusion, this is the first proteomic analysis of S. sisymbriifolium under V. dahliae stress.

Viruses deploy numerous strategies to infect plants, typically by forming complexes with another virus, leading to more efficient infection. However, the detailed plant responses to viral infection and the underlying mechanisms of co-infection remain unclear. Previously, we found that tomato spotted wilt orthotospovirus (TSWV) and Hippeastrum chlorotic ringspot orthotospovirus (HCRV) could infect plants in the field by forming a complex. In this study, we found that TSWV infected tobacco (Nicotiana benthamiana) plants in cooperation with HCRV, leading to a more efficient infection rate of both viruses. We then used the in-depth full-length transcriptome to analyze the responses of N. benthamiana to complex infection by TSWV–HCRV (TH). We found that infection with individual TSWV and HCRV triggered plant defense responses, including the jasmonic acid signaling pathway, autophagy, and secondary metabolism. However, TH co-infection could not trigger and even suppress some genes that are involved in these basal resistance responses, suggesting that co-infection is advantageous for the virus and not for the plants. Typically, the TH complex inhibits NbPR1 expression to suppress tobacco resistance. Moreover, the TH complex could alter the expression of microRNAs (miRNAs), especially novel-m0782-3p and miR1992-3p, which directly interact with NbSAM and NbWRKY6 and suppress their expression in tobacco, leading to downregulation of NbPR1 and loss of resistance in tobacco to TSWV and HCRV viruses. Overall, our results elucidated the co-infection mechanisms of TH in tobacco by deploying the miRNA of plants to suppress plant basal resistance and contributed to developing a novel strategy to control crop disease caused by this virus complex.