Effect Of Quorum Sensing Signal Molecule AHLs On The Morphology Establishment And Regulatory Of Poplar (Populus × Euramericana 'Neva') Seedling Fine Roots

Fine roots and bacteria can interact with each other through the conduction of small-molecule signal substances.This regulation mechanism is called the Quorum sensing(QS).Gram-negative bacteria can secrete small-molecule N-acyl-homoserine lactones(AHLs).The fine roots of plants can sense the AHLs signal around them and regulate the growth of plant roots.In this study,N-octanoyl-DL-homoserine lactone(C8-HSL)isolated from the rhizosphere soil of poplar was selected as the signal molecule.The effects of different concentrations of C8-HSL on the morphology and anatomical structure of poplar fine roots were studied.The interaction between the leaf parts of the aerial parts and the fine roots of the underground parts;the relationship between AHLs and CHS gene levels was obtained through transcriptome sequencing,in order to obtain the effect and influence of the group-sensing signal AHLs on the growth of Populus × euramericana `I-107'.The transmission mechanism of group-sense signals in plants provides theoretical support.The results of the study are as follows:1?Exogenously added different concentrations of homoserine lactone(AHLs).The effect of AHLs on the fine roots of poplars with different diameters was found that the length of fine roots,the number of root tips,and the surface area of fine roots of 0-0.5mm diameter were greater than those of 0.5-1.0mm diameter lever;root volume was smaller.AHLs had significant concentration effect,showing the law of low concentration promotion and higher concentrations inhibition,in the range of 4-8?mol/L,root morphological changes was significantly promoted;and in the range of 12-20?mol/L,root morphology changes had been significantly suppressed.The effect of AHLs on the growth dynamics of fine roots showed a slow growth in the early stage,a fast growth rate in the middle period,and a slower trend in the later period.2?Exogenous addition of AHLs had a significant effect on the anatomical structure of poplar fine roots.With the increase of AHLs concentrations gradient,the diameter of root cross-section,cortical thickness,and diameter of vascular bundle all showed the trend of low concentration promoting growth and high concentration inhibition increasing.The diameter of catheter gradually decreased with the change of root sequence.3?The leaf area gradually increased with the increase of AHLs concentration,but the upward trend was slow,and there was no significant difference between different concentration treatments.The chlorophyll content in leaves(Chl a+b)also showed that the chlorophyll content gradually increased with the increase of concentration gradient.However,the difference was not significant,while Chl a/b showed a gradual decrease with increasing concentration.4?Through the transcriptome sequencing of poplar fine roots under the influence of different concentrations of AHLs,four chalcone synthases(CHS)genes were screened in response to AHLs.Quantitative fluorescence analysis showed that the concentration of C8-HSL increased,and the expression of CHS gene showed different changes.This shows that the reduction of chalcone synthase in plants has a certain relationship with root growth.