Biology subjects

Xia, T.

Publications and source records attributed to Xia, T..

3 recordsLinked to original sources

bioRxiv2018

A multidrug resistant clinical P. aeruginosa isolate in the MLST550 clonal complex: uncoupled quorum sensing modulates the interplay of virulence and resistance

Pseudomonas aeruginosa is a prevalent and pernicious pathogen equipped with both extraordinary capabilities to infect the host and to develop antimicrobials resistance (AMR). Monitoring the emergence of AMR high risk clones and understanding the interplay of their pathogenicity and antibiotic resistance is of paramount importance to avoid resistance dissemination and to control P. aeruginosa infections. In this study, we report the identification of a multidrug resistant (MDR) P. aeruginosa strain PA154197 isolated from a blood stream infection in Hong Kong. PA154197 belongs to a distinctive MLST550 clonal complex shared by two international P. aeruginosa isolates VW0289 and AUS544. Comparative genome and transcriptome analysis with the reference strain PAO1 led to the identification of a variety of genetic variations in antibiotic resistance genes and the hyper-expression of three multidrug efflux pumps MexAB-OprM, MexEF-OprN, and MexGHI-OpmD in PA154197. Unlike many resistant isolates displaying an attenuated virulence, PA154197 produces a significantly high level of the P. aeruginosa major virulence factor pyocyanin (PYO) and displays an uncompromised virulence compared to PAO1. Further analysis revealed that the secondary quorum sensing system Pqs which primarily controls the PYO production is hyper-active in PA154197 independent of the master QS systems Las and Rhl. Together, these investigations disclose a unique, uncoupled QS mediated pathoadaptation mechanism in clinical P. aeruginosa which may account for the high pathogenic potentials and antibiotics resistance in the MDR isolate PA154197.

microbiology↗

bioRxiv2017

Isolation And Characterization Of Key Genes That Promote Flavonoid Accumulation In Purple-Leaf Tea (Camellia sinensis L.)

There were several high concentrations of flavonoid components in tea leaves that present health benefits. A novel purple-leaf tea variety, Mooma1, was obtained from the natural hybrid population of Longjing 43 variety. The buds and young leaves of Mooma1 were displayed in bright red. HPLC and LC-MS analysis showed that anthocyanins and O-Glycosylated flavonols were remarkably accumulated in the leaves of Mooma1, while the total amount of catechins in purple-leaf leaves was slightly decreased compared with the control. A R2R3-MYB transcription factor (CsMYB6A) and a novel UGT gene (CsUGT72AM1), that were highly expressed in purple leaf were isolated and identified by transcriptome sequencing. The over-expression of transgenic tobacco confirmed that CsMYB6A can activate the expression of flavonoid-related structural genes, especially CHS and 3GT, controlling the accumulation of anthocyanins in the leaf of transgenic tobacco. Enzymatic assays in vitro confirmed that CsUGT72AM1 has catalytic activity as a flavonol 3-O-glucosyltransferase, and displayed broad substrate specificity. The results were useful for further elucidating the molecular mechanisms of the flavonoid metabolic fluxes in the tea plant.

plant biology↗

bioRxiv2016

Ubiquitylation activates a peptidase that promotes cleavage and destabilization of its activating E3 ligases and diverse growth regulatory proteins to limit cell proliferation in Arabidopsis

The characteristic shapes and sizes of organs are established by cell proliferation patterns and final cell sizes, but the underlying molecular mechanisms coordinating these are poorly understood. Here we characterize a ubiquitin-activated peptidase called DA1 that limits the duration of cell proliferation during organ growth in Arabidopsis thaliana. The peptidase is activated by two RING E3 ligases, BB and DA2, which are subsequently cleaved by the activated peptidase and destabilized. In the case of BB, cleavage leads to destabilization by the RING E3 ligase PRT1 of the N-end rule pathway. DA1 peptidase activity also cleaves the de-ubiquitylase UBP15, which promotes cell proliferation, and the transcription factors TCP15 and TCP22, which promote cell proliferation proliferation and repress endoreduplication. We propose that DA1 peptidase activity regulates the duration of cell proliferation and the transition to endoreduplication and differentiation during organ formation in plants by coordinating the destabilization of regulatory proteins.

plant biology↗