Balanced callose and cellulose biosynthesis in Arabidopsis quorum-sensing signaling and pattern-triggered immunity.

The plant cell wall (CW) is one of the most important physical barriers that phytopathogens must conquer to invade their hosts. This barrier is a dynamic structure that responds to pathogen infection through a complex network of immune receptors, together with CW-synthesizing and CW-degrading enzymes. Callose deposition in the primary CW is a well-known physical response to pathogen infection. Notably, callose and cellulose biosynthesis share an initial substrate, UDP-glucose, which is the main load-bearing component of the CW. However, how these 2 critical biosynthetic processes are balanced during plant-pathogen interactions remains unclear. Here, using 2 different pathogen-derived molecules, bacterial flagellin (flg22) and the diffusible signal factor (DSF) produced by Xanthomonas campestris pv. campestris, we show a negative correlation between cellulose and callose biosynthesis in Arabidopsis (Arabidopsis thaliana). By quantifying the abundance of callose and cellulose under DSF or flg22 elicitation and characterizing the dynamics of the enzymes involved in the biosynthesis and degradation of these 2 polymers, we show that the balance of these 2 CW components is mediated by the activity of a ß-1,3-glucanase (BG2). Our data demonstrate balanced cellulose and callose biosynthesis during plant immune responses.

Biodegradation of highly crystallized poly(ethylene terephthalate) through cell surface codisplay of bacterial PETase and hydrophobin.

The process of recycling poly(ethylene terephthalate) (PET) remains a major challenge due to the enzymatic degradation of high-crystallinity PET (hcPET). Recently, a bacterial PET-degrading enzyme, PETase, was found to have the ability to degrade the hcPET, but with low enzymatic activity. Here we present an engineered whole-cell biocatalyst to simulate both the adsorption and degradation steps in the enzymatic degradation process of PETase to achieve the efficient degradation of hcPET. Our data shows that the adhesive unit hydrophobin and degradation unit PETase are functionally displayed on the surface of yeast cells. The turnover rate of the whole-cell biocatalyst toward hcPET (crystallinity of 45%) dramatically increases approximately 328.8-fold compared with that of purified PETase at 30 °C. In addition, molecular dynamics simulations explain how the enhanced adhesion can promote the enzymatic degradation of PET. This study demonstrates engineering the whole-cell catalyst is an efficient strategy for biodegradation of PET.

Efficient biodegradation of highly crystallized polyethylene terephthalate through cell surface display of bacterial PETase.

Polyethylene terephthalate (PET) is one of the most widely used plastics in the world. Accumulation of the discarded PET in the environment is creating a global environmental problem. Recently, a bacterial enzyme named PETase was found to have the novel ability to degrade the highly crystallized PET. However, the enzymatic activity of native PETase is still low limiting its possible use in recycling of PET. In this study, we developed a whole-cell biocatalyst by displaying PETase on the surface of yeast (Pichia pastoris) cell to improve its degradation efficiency. Our data shows that PETase could be functionally displayed on the yeast cell with enhanced pH and thermal stability. The turnover rate of the PETase-displaying yeast whole-cell biocatalyst towards highly crystallized PET dramatically increased about 36-fold compared with that of purified PETase. Furthermore, the whole-cell biocatalyst showed stable turnover rate after seven repeated use and under some chemical/solvent conditions, and its ability to degrade different commercial highly crystallized PET bottles. Our results reveal that PETase-displaying whole-cell biocatalyst affords a promising route for efficient biological recycling of PET.

Method for quantitative detection of FAM19A4 by flow cytometry using latex beads as solid carrier.

FAM19A4 (family with sequence similarity 19 member A4; also TAFA4) is a classical secretory protein expressed mainly in the central nervous system and upregulated significantly in lipopolysaccharide (LPS)-stimulated monocytes and macrophages. It is a novel cytokine ligand of formyl peptide receptor 1 (FPR1), showing chemotactic activities on macrophages and promoting the phagocytosis capacity and the release of reactive oxygen species (ROS) by macrophages upon zymosan stimulation. Based on the same detection principle as enzyme-linked immunosorbent assay (ELISA), we developed a sandwich immunoassay for quantitative detection of FAM19A4 in biological fluids by flow cytometry, with latex beads as solid carrier. The method showed good performance in a wide range of 39-10,000 pg/mL and possessed excellent specificity, good precision, and favorable recovery in several different matrices. Native FAM19A4 secreted by phorblo 12-myristate 13-acetate (PMA) and LPS stimulated THP-1 cells could also be detected by this method. This method will be much helpful to FAM19A4 studies.