Potential roles for pattern molecule of PAMP-triggered immunity in improving crop cold tolerance

KEY MESSAGE

The application of flagellin 22 (flg22), the most widely studied PAMP, enhance crop cold tolerance. ICE1-CBF pathway and SA signaling is involved in the alleviation of cold injury by flg22 treatment. Pathogen infection cross-activates cold response and increase cold tolerance of host plants. However, it is not possible to use the infection to increase cold tolerance of field plants. Here flagellin 22 (flg22), the most widely studied PAMP (pathogen-associated molecular patterns), was used to mimic the pathogen infection to cross-activate cold response. Flg22 treatment alleviated the injury caused by freezing in Arabidopsis, oilseed and tobacco. In Arabidopsis, flg22 activated the expression of immunity and cold-related genes. Moreover, the flg22 induced alleviation of cold injury was lost in NahG transgenic line (SA-deficient), sid2-2 and npr1-1 mutant plants, and flg22-induced expression of cold tolerance-related genes, which indicating that salicylic acid signaling pathway is required for the alleviation of cold injury by flg22 treatment. In short flg22 application can be used to enhance cold tolerance in field via a salicylic acid-depended pathway.

Childhood co-exposure of cold stress and PM2.5 aggravates the susceptibility and severity of asthma in adulthood of mice

Both cold stress and ambient fine particle particulate matter (PM_2.5 ) has been reported to aggravate and induce respiratory problems like asthma, but the mechanism involved in that has not been fully understood. Therefore, the present study is to explore the mechanism involved in the increased susceptibility and severity of asthma caused by cold stress and PM_2.5 exposure. Urban PM_2.5 of Shanghai was concentrated to simulate a PM_2.5 -polluted environment with an average concentration of 400 μg/m³ , where 1-month young C57BL/6J mice were exposed for 2 months under cold stress (2°C). Co-exposure of cold stress and PM_2.5 in childhood of mice led to significant infiltration of inflammatory cells in the peribronchial region or airspaces and the thickening or fibrosis of alveolar septum, increased OVA-specific IgE in serum and total cells, eosinophil cells, and the levels of inflammatory cytokines including IL-4, IL-8, IL-1β, IL-5, IL-13, and IFN-γ in bronchoalveolar lavage fluid (BALF) of asthma mice. Moreover, mice in co-exposure group presented a significantly high cough feature, reduced catalase (CAT), glutathione (GSH), superoxide dismutase (SOD), and elevated malonaldehyde (MDA) elevated in BALF; increased ratio of Th2/Th1 and the markable inhibition of Th17 differentiation toward Treg cells in the adulthood of asthma mice. Cold stress and PM_2.5 co-exposure in childhood may promote the deterioration of asthma symptoms in adulthood of mice by increasing inflammatory cytokines, ROS formation, Th2/Th1 imbalance, and suppressing the differentiation of Th17 toward Treg cells, which will help to provide experimental references when making some therapeutic strategies in allergic diseases through focusing on some natural solutions.

Molecular and functional analyses of novel anti-lipopolysaccharide factors in giant river prawn (Macrobrachium rosenbergii, De Man) and their expression responses under pathogen and temperature exposure

Anti-lipopolysaccharide factor (ALF) is an immune-related protein that is crucially involved in immune defense mechanisms against invading pathogens in crustaceans. In the current study, three different ALFs of giant river prawn (Mr-ALF3, Mr-ALF8 and Mr-ALF9) were discovered. Based on sequence analysis, Mr-ALF3 and Mr-ALF9 were identified as new members of ALFs in crustaceans (groups F and G, respectively). Structurally, each newly identified Mr-ALF contained three α-helices packed against a four-stranded β-sheet bearing the LPS-binding motif, which usually binds to the cell wall components of bacteria. Tissue expression analysis using quantitative real-time RT-PCR (qRT-PCR) demonstrated that Mr-ALF3 was expressed in most tissues, and the highest expression was in the heart and hemocytes. The Mr-ALF8 gene was highly expressed in the heart, hemocytes, midgut, hepatopacreas and hindgut, respectively, while the Mr-ALF9 gene was modestly expressed in the heart and hemocytes, respectively. The transcriptional responses of the Mr-ALFs to Aeromonas hydrophila and hot/cold temperatures were investigated by qRT-PCR in the gills, hepatopancreas and hemocytes. We found that all Mr-ALFs were clearly suppressed in all tested tissues when the experimental prawns were exposed to extreme temperatures (25 and 35 °C). Moreover, the expression levels of these genes were significantly induced in all examined tissues by 2 different concentrations of A. hydrophila (1 × 10⁶ and 1 × 10⁹ CFU/ml), particularly 12 and 96 h after the injection. Finally, binding activity analysis of LPS-motif peptides of each Mr-ALF revealed that the LPS peptide of Mr-ALF3 exhibited the strongest adhesion to two pathogenic Gram-negative bacteria, A. hydrophila and Vibrio harveyi, and the non-pathogenic Gram-positive Bacillus megaterium. The results also showed that the Mr-ALF8 and Mr-ALF9 peptides had mild antimicrobial effects against similar tested bacteria. Based on information obtained in this study, novel ALF genes were clearly identified. Analyses of their responses under pathogenic and temperature stresses demonstrated the binding and antimicrobial activities of these ALFs and the consequent physiological effects, indicating their crucial functional roles in the prawn immune system.