Plant flavonoids target Pseudomonas syringae pv. tomato DC3000 flagella and type III secretion system.

Flavonoids are among the most abundant plant secondary metabolites involved in plant protection against pathogens, but micro-organisms have developed resistance mechanisms to those compounds. We previously demonstrated that the MexAB-OprM efflux pump mediates resistance of Pseudomonas syringae pv. tomato (Pto) DC3000 to flavonoids, facilitating its survival and the colonization of the host. Here, we have shown that tomato plants respond to Pto infection producing flavonoids and other phenolic compounds. The effects of flavonoids on key traits of this model plant-pathogen bacterium have also been investigated observing that they reduce Pto swimming and swarming because of the loss of flagella, and also inhibited the expression and assembly of a functional type III secretion system. Those effects were more severe in a mutant lacking the MexAB-OprM pump. Our results suggest that flavonoids inhibit the function of the GacS/GacA two-component system, causing a depletion of rsmY RNA, therefore affecting the synthesis of two important virulence factors in Pto DC3000, flagella and the type III secretion system. These data provide new insights into the flavonoid role in the molecular dialog between host and pathogen.

Caracterización morfológica y molecular del antagonismo entre el endofito Diaporthe sp. aislado de frailejón (Espeletia sp.) y el fitopatógeno Phytophthora infestans / Morphological and molecular characterization of the antagonistic interaction between the endophyte Diaporthe sp. isolated from frailejón (Espeletia sp.) and the plant pathogen Phytophthora infestans

Los hongos endofitos son organismos que se caracterizan por liberar una gran variedad de metabolitos secundarios al medio. En el presente estudio se caracterizó la capacidad de un hongo endofito con micelio estéril aislado de Espeletia sp. para controlar al fitopatógeno de la patata Phytophthora infestans. La secuencia de las regiones internal transcribed spacer (ITS) del hongo mostró un 94% de similitud con la de Diaporthe phaseolorum. La interacción antagónica entre Diaporthe sp. y P. infestans se evaluó en 3 medios de cultivo: agar papa dextrosa (PDA), jugo V8 y Czapek. En las pruebas duales se observó el efecto antagonista que ejerció Diaporthe sp. en el crecimiento de P. infestans, que mostró diferencias en el efecto inhibitorio de acuerdo con el medio usado. Se detectó una expresión diferencial del gen que codifica para la amilasa durante el antagonismo(AU)

Endophyticfungiproduceagreatvarietyofsecondarymetabolitesboth in vivo and in vitro. Inthisstudy,we characterizedtheabilityofasterile-myceliumendophyticfungusisolatedfrom Espeletia sp. tocontrolthe growthof Phytophthorainfestans in Petridishes.SequencefromtheITSregions(internaltranscribedspacer) oftheendophyteshowed94%similarityto Diaporthe phaseolorum’s. Theantagonisticinteractionbetween Diaporthe sp. and P.infestans wasevaluatedinthreedifferentculturemedia. Diaporthe sp. showedan antagonisticeffecttowards P.infestans, with somevariationdependingonwhichmediumwasused.Inan attempttoidentifypossiblegenesinvolvedinthisantagonism,wedetectedagenefromtheendophyteencoding anamylase,whichwasdifferentiallyexpressedduringthisbioticinteraction(AU)

[Morphological and molecular characterization of the antagonistic interaction between the endophyte Diaporthe sp. isolated from frailejón (Espeletia sp.) and the plant pathogen Phytophthora infestans]. / Caracterización morfológica y molecular del antagonismo entre el endofito Diaporthe sp. aislado de frailejón (Espeletia sp.) y el fitopatógeno Phytophthora infestans.

Endophytic fungi produce a great variety of secondary metabolites both in vivo and in vitro. In this study, we characterized the ability of a sterile-mycelium endophytic fungus isolated from Espeletia sp. to control the growth of Phytophthora infestans in Petri dishes. Sequence from the ITS regions (internal transcribed spacer) of the endophyte showed 94% similarity to Diaporthe phaseolorum's. The antagonistic interaction between Diaporthe sp. and P. infestans was evaluated in three different culture media. Diaporthe sp. showed an antagonistic effect towards P. infestans, with some variation depending on which medium was used. In an attempt to identify possible genes involved in this antagonism, we detected a gene from the endophyte encoding an amylase, which was differentially expressed during this biotic interaction.