Therapeutics that target the virulence of pathogens rather than their viability offer a promising alternative for treating infectious diseases and circumventing antibiotic resistance. In this study, we searched for anti-virulence compounds against Pseudomonas aeruginosa from Chinese herbs and investigated baicalin from Scutellariae radix as such an active anti-virulence compound. The effect of baicalin on a range of important virulence factors in P. aeruginosa was assessed using luxCDABE-based reporters and by phenotypical assays. The molecular mechanism of the virulence inhibition by baicalin was investigated using genetic approaches. The impact of baicalin on P. aeruginosa pathogenicity was evaluated by both in vitro assays and in vivo animal models. The results show that baicalin diminished a plenty of important virulence factors in P. aeruginosa, including the Type III secretion system (T3SS). Baicalin treatment reduced the cellular toxicity of P. aeruginosa on the mammalian cells and attenuated in vivo pathogenicity in a Drosophila melanogaster infection model. In a rat pulmonary infection model, baicalin significantly reduced the severity of lung pathology and accelerated lung bacterial clearance. The PqsR of the Pseudomonas quinolone signal (PQS) system was found to be required for baicalin’s impact on T3SS. These findings indicate that baicalin is a promising therapeutic candidate for treating P. aeruginosa infections.

Heat shock proteins (HSPs) play important biological roles, and they are implicated in bacterial response to environmental stresses and in pathogenesis of infection. The role of HSPs in P. aeruginosa, however, remains to be fully elucidated. Here, we report the unique role of HSP DnaJ in biofilm formation and pathogenicity in P. aeruginosa. A dnaJ mutant produced hardly any pyocyanin and formed significantly less biofilms, which contributed to decreased pathogenicity as demonstrated by reduced mortality rate in a Drosophila melanogaster infection model. The reduced pyocyanin production in the dnaJ mutant was a result of the decreased transcription of phenazine synthesis operons including phzA1, phzA2, phzS, and phzM. The reduction of biofilm formation and initial adhesion in the dnaJ mutant could be reversed by exogenously added pyocyanin or extracellular DNA (eDNA). Consistent with such observations, absence of dnaJ significantly reduced the release of eDNA in P. aeruginosa and addition of exogenous pyocyanin could restore eDNA release. These results indicate dnaJ mutation caused reduced pyocyanin production, which in turn caused the decreased eDNA, resulting in decreased biofilm formation. DnaJ is required for pyocyanin production and full virulence in P. aeruginosa; it affects biofilm formation and initial adhesion via pyocyanin, inducing eDNA release.

Hybridization and polyploidization have made great contributions to speciation, heterosis, and agricultural production within plants, but there is still limited understanding and utilization in animals. Subgenome structure and expression reorganization and cooperation post hybridization and polyploidization are essential for speciation and allopolyploid success. However, the mechanisms have not yet been comprehensively assessed in animals. Here, we produced a high-fidelity reference genome sequence for common carp, a typical allotetraploid fish species cultured worldwide. This genome enabled in-depth analysis of the evolution of subgenome architecture and expression responses. Most genes were expressed with subgenome biases, with a trend of transition from the expression of subgenome A during the early stages to that of subgenome B during the late stages of embryonic development. While subgenome A evolved more rapidly, subgenome B contributed to a greater level of expression during development and under stressful conditions. Stable dominant patterns for homoeologous gene pairs both during development and under thermal stress suggest a potential fixed heterosis in the allotetraploid genome. Preferentially expressing either copy of a homoeologous gene at higher levels to confer development and response to stress indicates the dominant effect of heterosis. The plasticity of subgenomes and their shifting of dominant expression during early development, and in response to stressful conditions, provide novel insights into the molecular basis of the successful speciation, evolution, and heterosis of the allotetraploid common carp.

The diploid Poropuntius huangchuchieni in the cyprinid family, which is widely distributed in the Mekong and Red River basins, is one of the most closely related diploid progenitor‐like species of allotetraploid common carp, which was generated by merging of two diploid genomes during evolution. Therefore, the P. huangchuchieni genome is essential for polyploid evolution studies in Cyprinidae. Here, we report a high‐quality chromosome‐level genome assembly of P. huangchuchieni by integrating Oxford Nanopore and Hi‐C technologies. The assembled genome size was 1,021.38 Mb, 895.66 Mb of which was anchored onto 25 chromosomes with a N50 of 32.93 Mb. The genome contained 486.28 Mb repetitive elements and 24,099 protein‐coding genes. Approximately 95.9% of the complete BUSCOs were detected, suggesting a high completeness of the genome. Evolutionary analysis revealed that P. huangchuchieni diverged from Cyprinus carpio at approximately 12 Mya. Genome comparison between P. huangchuchieni and the B subgenome of C. carpio provided insights into chromosomal rearrangements during the allotetraploid speciation. With the complete gene set, 17,474 orthologous genes were identified between P. huangchuchieni and C. carpio, providing a broad view of the gene component in the allotetraploid genome, which is critical for future genetic analyses. The high‐quality genomic data set created for P. huangchuchieni provides a diploid progenitor‐like reference for the evolution and adaptation of allotetraploid carps.