Biology subjects

Hao, G.

Publications and source records attributed to Hao, G..

3 recordsLinked to original sources

bioRxiv2021

Two Liberibacter Effectors Combine to Suppress Critical Innate Immune Defenses and Facilitate Huanglongbing Pathogenesis in Citrus

Genome sequence analyses predicted the presence of effectors in the gram-negative Candidatus Liberibacter asiaticus (CLas) even without the presence of a classical type III secretion system. Since CLas is not culturable, it is not possible to perform traditional gene knockout experiments to determine the role of various effectors in Huanglongbing (HLB) pathogenesis. Therefore, we followed an alternative functional genomics approach to examine the role of the CLas effectors in HLB pathogenesis in general and more specifically in suppressing citrus innate immune response. Here, we focused on the CLas effectors, P235 and Effector 3, to perform the following studies. First, proteomic studies by LC-MS/MS were conducted to screen the putative interacting citrus protein partners of P235 and Effector 3 from the healthy and CLas-infected Hamlin extracts and the most probable candidates were identified based upon their high protein scores from LC-MS/MS. Second, a transgenic tobacco split GFP system was designed for in planta detection of the most probable citrus interacting protein partners of P235 and Effector 3. Third, in vitro and in planta studies were performed to show that each of two effectors interacts with and inhibits the functions of multiple citrus proteins belonging to the innate immune pathways. These inhibitory interactions led to a high level of reactive oxygen species (ROS), blocking of bactericidal lipid binding protein (LTP), and induction of premature programmed cell death (PCD), thereby supporting CLas infection and HLB pathogenesis. Finally, an LTP mimic was designed to sequester and block the CLas effector and to rescue the bactericidal activity of LTP.

plant biology↗

bioRxiv2021

Mosaic Evolution of Beta Barrel Porin Encoding Genes in Escherichia coli

Bacterial porins serve as the interface interacting with extracellular environment, and are often found under positive selection to fit in different environmental stresses. Local recombination has been identified in a handful of porin genes to facilitate the rapid adaptation of bacterial cells. It remains unknown whether it is a common evolutionary mechanism in gram-negative bacteria for all or a majority of the outer membrane proteins. In this research, we investigated the {beta}-barrel porin encoding genes in Escherichia coli that were reported under positive Darwinia selection. Besides fhuA that was found with ingenic local recombination predominantly previously, we identified four other genes, i.e., lamB, ompA, ompC and ompF, all showing the similar mosaic evolution patterns as in fhuA. Comparative analysis of the protein sequences disclosed a list of highly variable regions in each protein family, which are mostly located in the convex of extracellular loops and coinciding with the binding sites of various bacteriophages. For each of the porin family, mosaic recombination leads to various combinations of the HVRs with different sequence patterns, generating diverse protein groups. Structure modeling further indicated the conserved global topology for various groups of each porin family, but the extracellular surface varies a lot that is formed by individual or combinatorial HVRs. The conservation of global tertiary structure ensures the channel activity while the wide diversity of HVRs may assist bacteria avoiding the invasion of phages, antibiotics or immune surveillance factors. In summary, the study identified multiple bacterial porin genes with mosaic evolution, a likely general strategy, by which outer membrane proteins could facilitate the host bacteria to both maintain normal life processes and evade the attack of unflavored environmental factors rapidly. ImportanceMicroevolution studies can disclose more elaborate evolutionary mechanisms of genes, appearing especially important for genes with multifaceted function such as those encoding outer membrane proteins. However, in most cases, the gene is considered as a whole unit and the evolutionary patterns are disclosed. In this research, we reported that multiple bacterial porin proteins follow mosaic evolution, with local ingenic recombination combined with spontaneous mutations based positive Darwinia selection, and conservation for most of the other regions. It could represent a common mechanism for bacterial outer membrane proteins. The study also provides insights on development of new anti-bacterial agent or vaccines.

microbiology↗

bioRxiv2021

Vaccination-induced rapid protection against bacterial pneumonia via training alveolar macrophage in mice

Vaccination strategies for rapid protection against multidrug-resistant bacterial infection are very important, especially for hospitalized patients who have high risk of exposure to these bacteria. However, few such vaccination strategies exist due to a shortage of knowledge supporting their rapid effect. Here we demonstrated a single intranasal immunization of inactivated whole cell (IWC) of Acinetobacter baumannii elicits rapid protection against A. baumannii-infected pneumonia via training of innate immune response in Rag1-/- mice. Immunization-trained alveolar macrophages (AMs) showed enhanced TNF- production upon restimulation. Adoptive transfer of immunization-trained AMs into naive mice mediated rapid protection against infection. Elevated TLR4 expression on vaccination-trained AMs contributed to rapid protection. Moreover, immunization-induced rapid protection was also seen in Pseudomonas aeruginosa and Klebsiella pneumoniae pneumonia models, but not in Staphylococcus aureus and Streptococcus pneumoniae model. Our data reveal that a single intranasal immunization induces rapid and efficient protection against certain Gram-negative bacterial pneumonia via training AMs response, which highlights the importance and the possibility of harnessing trained immunity of AMs to design rapid-effecting vaccine.

immunology↗