Flowers can provide a protected and nutrient-rich environment to the epiphytic microflora,thus representing a sensible entry point for pathogens such as Pseudomonas syringae pv.actinidiae(Psa).This bacterium can colon...Flowers can provide a protected and nutrient-rich environment to the epiphytic microflora,thus representing a sensible entry point for pathogens such as Pseudomonas syringae pv.actinidiae(Psa).This bacterium can colonize both male and female Actinidia flowers,causing flower browning and fall,and systemic invasion of the host plant,eventually leading to its death.However,the process of flower colonization and penetration into the host tissues has not yet been fully elucidated.In addition,the presence of Psa in the pollen from infected flowers,and the role of pollination in the spread of Psa requires confirmation.The present study employed a Psa strain constitutively expressing the fluorescent GFPuv protein,to visualize in vivo flower colonization.Microscopy observations were performed by means of confocal laser scanning and wide-field fluorescent microscopy,and were coupled with the study of Psa population dynamics by quantitative PCR(q-PCR).The pathogen was shown to colonize stigmata,move along the stylar furrow,and penetrate the receptacles via the style or nectarhodes.Once the receptacle was invaded,the pathogen migrated along the flower pedicel and became systemic.Psa was also able to colonize the anthers epiphytically and endophytically.Infected male flowers produced contaminated pollen,which could transmit Psa to healthy plants.Finally,pollinators(Apis mellifera and Bombus terrestris)were studied in natural conditions,showing that,although they can be contaminated with Psa,the pathogen’s transmission via pollinators is contrasted by its short survival in the hive.展开更多
基金The work was funded by the European Union’s Seventh Framework Program for research,technological development,and demonstration under grant agreement no 613678(DROPSA—Strategies to develop effective,innovative,and practical approaches to protect major European fruit crops from pests and pathogens).
文摘Flowers can provide a protected and nutrient-rich environment to the epiphytic microflora,thus representing a sensible entry point for pathogens such as Pseudomonas syringae pv.actinidiae(Psa).This bacterium can colonize both male and female Actinidia flowers,causing flower browning and fall,and systemic invasion of the host plant,eventually leading to its death.However,the process of flower colonization and penetration into the host tissues has not yet been fully elucidated.In addition,the presence of Psa in the pollen from infected flowers,and the role of pollination in the spread of Psa requires confirmation.The present study employed a Psa strain constitutively expressing the fluorescent GFPuv protein,to visualize in vivo flower colonization.Microscopy observations were performed by means of confocal laser scanning and wide-field fluorescent microscopy,and were coupled with the study of Psa population dynamics by quantitative PCR(q-PCR).The pathogen was shown to colonize stigmata,move along the stylar furrow,and penetrate the receptacles via the style or nectarhodes.Once the receptacle was invaded,the pathogen migrated along the flower pedicel and became systemic.Psa was also able to colonize the anthers epiphytically and endophytically.Infected male flowers produced contaminated pollen,which could transmit Psa to healthy plants.Finally,pollinators(Apis mellifera and Bombus terrestris)were studied in natural conditions,showing that,although they can be contaminated with Psa,the pathogen’s transmission via pollinators is contrasted by its short survival in the hive.
