The Effect of Bacterial AHL on the Cyclic Adenosine Monophosphate Content in Plants According to High-Performance Liquid Chromatography.

Cyclic adenosine monophosphate (cAMP) is an important second messenger in cells, mediating various stimulation signals such as the growth and development of organisms and stress and participating in regulating various biological processes of cells. This article explores the quantitative determination of cAMP in plants using High-Performance Liquid Chromatography (HPLC) and applies this method to analyzing the changes in cAMP content during the process of plant response to the bacterial quorum sensing signal N-acyl homoserine lactone (AHL). Research has shown that the optimal detection conditions for HPLC are as follows: the chromatographic column is Venusil MP C18 (2), the mobile phase is methanol-water (0.1% trifluoroacetic acid) (v:v, 10:90), the detection wavelength is 259 nm, the column temperature is 35 °C, and the flow rate is 0.8 mL/min. The precision of the standard sample of this method is 98.21%, the precision of the sample is 98.87%, and the recovery rate is 101.067%. The optimal extraction conditions for cAMP in Arabidopsis are to use 15% methanol ultrasonic extraction for 10 min, followed by a 40 °C water bath for 4 h. Bacterial AHL signal processing can significantly stimulate an increase in cAMP levels in Arabidopsis leaves and roots. The establishment of HPLC detection methods for the cAMP content in plants is of great significance for in-depth research on the signal transduction mechanisms of plant-bacterial interactions.

[Drying Process and Model of Banqiao Codonopsis Radix Slice in Air-impingement Jet Dryer].

Objective: To determine the drying process and to built model of Banqiao Codonopsis Radix slices dried in air-impingement jet dryer. Methods: With taking the content of polysaccharides( CPPS),rehydration ratio( RR) and drying time as the evaluation indexes,the effects of drying temperature( 40,50,60 and 70 ℃),slices thickness( 1,2,3 and 4 mm) and air velocity( 8,10,12,and 14 m / s) on the content of CPPS,RR and drying time were studied. With taking the R2,χ2and RMSE as the evaluation indexes,the optimum model was screened by fitting the drying curves data with four selected models. Results: The variety of all studied factors lead to change of the content of CPPS,RR and drying time,and the influence of air-temperature was most significant. Under the test conditions,the content of CPPS,RR and drying time were range from 20. 33% ~ 28. 26%,2. 65 ~ 3. 25 and 180 ~ 510 min, respectively. Among the four selected drying models, Modified Page model was the most suitable model to fit the drying curves data with the maximum average of R2( 0. 9993),the smallest average of χ2( 0. 00022) and the smaller average RMSE( 0. 01066). Conclusion: By comparison the content of CPPS,RR and drying time, the optimal drying process of Banqiao Codonopsis Radix slices dried in the air-impingement jet dryer was air temperature of 60 ℃,slice thickness of 2 mm and air velocity of 12 m / s. Under the drying conditions of air temperature 40 ~ 70 ℃,slice thickness 1 ~ 4 mm and air velocity 8 ~ 14 m / s, Modified Page model can effectively predict the moisture change of Banqiao Codonopsis Radix slice dried in air-impingement jet dryer.

Diffusible signal factor primes plant immunity against Xanthomonas campestris pv. campestris (Xcc) via JA signaling in Arabidopsis and Brassica oleracea.

Background: Many Gram-negative bacteria use quorum sensing (QS) signal molecules to monitor their local population density and to coordinate their collective behaviors. The diffusible signal factor (DSF) family represents an intriguing type of QS signal to mediate intraspecies and interspecies communication. Recently, accumulating evidence demonstrates the role of DSF in mediating inter-kingdom communication between DSF-producing bacteria and plants. However, the regulatory mechanism of DSF during the Xanthomonas-plant interactions remain unclear. Methods: Plants were pretreated with different concentration of DSF and subsequent inoculated with pathogen Xanthomonas campestris pv. campestris (Xcc). Pathogenicity, phynotypic analysis, transcriptome combined with metabolome analysis, genetic analysis and gene expression analysis were used to evaluate the priming effects of DSF on plant disease resistance. Results: We found that the low concentration of DSF could prime plant immunity against Xcc in both Brassica oleracea and Arabidopsis thaliana. Pretreatment with DSF and subsequent pathogen invasion triggered an augmented burst of ROS by DCFH-DA and DAB staining. CAT application could attenuate the level of ROS induced by DSF. The expression of RBOHD and RBOHF were up-regulated and the activities of antioxidases POD increased after DSF treatment followed by Xcc inoculation. Transcriptome combined with metabolome analysis showed that plant hormone jasmonic acid (JA) signaling involved in DSF-primed resistance to Xcc in Arabidopsis. The expression of JA synthesis genes (AOC2, AOS, LOX2, OPR3 and JAR1), transportor gene (JAT1), regulator genes (JAZ1 and MYC2) and responsive genes (VSP2, PDF1.2 and Thi2.1) were up-regulated significantly by DSF upon Xcc challenge. The primed effects were not observed in JA relevant mutant coi1-1 and jar1-1. Conclusion: These results indicated that DSF-primed resistance against Xcc was dependent on the JA pathway. Our findings advanced the understanding of QS signal-mediated communication and provide a new strategy for the control of black rot in Brassica oleracea.