Mitragyna speciosa (Kratom) is a tropical narcotic plant native to Southeast Asia with unique pharmacological properties. Here, we report the first chromosome-scale assembly of the M. speciosa genome. We employed PacBio sequencing to obtain a preliminary assembly, which was subsequently scaffolded using the chromatin contact mapping technique (Hi-C) into 22 pseudomolecules. The final assembly was 692 Mb with a scaffold N50 of 26 Mb. We annotated a total of 39,708 protein-coding genes, and our gene predictions recovered 98.4% of the highly conserved orthologs based on the BUSCO analysis. The phylogenetic analysis revealed that M. speciosa diverged from the last common ancestors of Coffea arabica and Coffea canephora approximately 47.6 million years ago. Our analysis of the sequence divergence at fourfold-degenerate sites from orthologous gene pairs provided evidence supporting a genome-wide duplication in M. speciosa, agreeing with the report that members of the genus Mitragyna are tetraploid. The STRUCTURE and principal component analyses demonstrated that the 85 M. speciosa accessions included in this study were an admixture of two subpopulations. The availability of our high-quality chromosome-level genome assembly and the transcriptomic resources will be useful for future studies on the alkaloid biosynthesis pathway, as well as comparative phylogenetic studies in Mitragyna and related species.

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The core nucleotide sequence of bovine (Bos taurus) testicular PH-20 hyaluronidase was cloned using one step RT-PCR. The 5' and 3' regions were cloned separately and a sequence overlap of 124 bp facilitated the fusion of these two fragments by overlapping PCR, resulting in a concatenated sequence of 1422 bp. This nucleotide sequence and its deduced amino acid sequence were compared to homologous sequences from eight other mammal species. The bovine sequences were most similar to those of the pig, Sus scrofa (swine Spam1: 79.1% nucleotide and 70.1% amino acid similarity) and least similar to sequences from the Norway rat, Rattus norvegicus (murine Spam1: 61% nucleotide and 53.3% amino acid similarity). A phylogenetic analysis joined the red fox (Vulpes vulpes) sequence as sister to the bull-pig pair. Twelve cysteine residues were conserved among all nine aligned amino acid sequences and five proposed glycosylation sites have been identified. The feasibility of developing an effective, low-cost bovine PH-20 expression system is discussed in light of these new data.

Papaya ringspot virus (PRSV) causes the Papaya ringspot disease. Virus-host interactions appear to play a significant role in the replication, pathogenesis, and infection caused by the PRSV. PRSV coat protein is likely to be involved in the processes of RNA replication, aphid transmission, and cell-to-cell movement, which is closely related to the host cell proteins resulting in a PRSV infection. To identify the host proteins that interact with the CP in vitro, immune precipitation, insolution trypsin digestion, and LC-MS/MS were performed. Twenty-three identified proteins that interacted with the CP are involved in cellular metabolism, transcription, signal, translation, carbohydrate metabolism, protein metabolism, stress response, photosynthesis, nucleotide metabolism, respiration, and lipid metabolism processes. The search tool for interactions of chemicals (STITCH) results show that SWP (an RNA polymerase II transcription mediator) and MPPBETA (Mitochondrial processing peptidase) are involved in known plant defense mechanisms including transcription factors, cell division, hormones, stress, mitochondrial electron transferase, respiration, and proteasome. Therefore, analyzing virus-host protein interactions at a molecular level is important to build a better understanding of the virus replication mechanism and cellular responses mounted against viruses by the host defense system.