Genome analysis of selected Pseudomonas syringae pv. aptata phytopathogenic strains and their biological control mediated by the Tip VI secretion system of Pseudomonas putida

[T. Ranković]

106 str.

Biologija - Biologija mikroorganizama / Biology - Biology of microorganisms

Ovaj rad predstavlja prvu studiju koja se bavi detaljnom analizom genoma i sekretoma fitopatogena Pseudomonas syringae pv. aptata i njihove biokontrole posredstvom Tip VI sekretornog sistema (T6SS) prirodnih izolata Pseudomonas putida. Posebnim osvrtom na analizu faktora virulencije P. syringae pv. aptata, pokazane su razlike u repertoaru gena za efektore Tip III sekretornog sistema (T3SS) između izrazito virulentnog soja P21 u odnosu na slabo virulentni P16. U genomu P21 identifikovani su geni za efektore AvrRpm1, HopAW1 i HopAU1 koji do sada nisu detektovani u P. syringae pv. aptata. Gajenjem P. syringae pv. aptata u uslovima koji imitiraju uslove u biljnom apoplastu uočeno je formiranje pila i pojačana sekrecija T3SS proteina. Većinom su efektori sekretovani u velikim količinama kod slabo virulentnih sojeva, dok su kod umereno i jako virulentnih prisutni u manjoj meri. P. putida S2/27 predstavlja jednog od najboljih kandidata za biološku kontrolu P21, inhibirajući rast patogena na kontakt-zavisan način. Za inhibiciju su potencijalno zaslužni i drugi mehanizmi pored T6SS. U odnosu na S2/27, gajenje u ko-kulturi sa P21 rezultuje smanjenom ekspresijom hcp1 gena, indikatora aktivnosti T6SS. U in planta testovima pokazano je da folijarna inokulacija ili tretman rizosfere suspenzijom P. putida S2/27 značajno utiče na redukciju simptoma izazvanih P21 na šećernoj repi. T6SS utiče na povećanu ekspresiju npr1 i nced gena uključenih u lokalni imunski odgovor biljke, dok pri sistemskom odgovoru ne dolazi do povećane ekspresije pomenutih gena. Dobijeni rezultati ukazuju da je patogeni potencijal P. syringae pv. aptata uslovljen diverzitetom gena i sekretovanih efektora uključenih u virulenciju. P. putida S2/27 poseduje potencijal za primenu u njihovoj biološkoj kontroli.

This study represents the first in-depth analysis of the genomes and secretomes of phytopathogenic Pseudomonas syringae pv. aptata and their biocontrol mediated by the Type VI secretion system (T6SS) of Pseudomonas putida. The main focus was an investigation of the virulence factors of P. syringae pv. aptata, revealing differences in the gene repertoire for the Type III secretion system (T3SS) effectors between the highly virulent strain P21 and the low-virulent strain P16. In the P21 genome we found genes for AvrRpm1, HopAW1, and HopAU1 effectors, which had not previously been detected in P. syringae pv. aptata. After incubation of P. syringae pv. aptata in apoplast-like conditions, the formation of pili and increased secretion of T3SS proteins were observed. Mainly, the T3SS effectors were highly secreted by the low-virulent strains, contrary to moderate and highly virulent strains. Among P. putida isolates, S2/27 represents one of the most promising candidates for biocontrol of P21 in a contact-dependent manner. Potentially, other mechanisms besides T6SS are involved in the observed inhibition. Compared to S2/27, incubation in co-culture with P21 led to downregulating the hcp1 gene, which is the indicator of T6SS activity. In planta, foliar or rhizosphere treatment with P. putida S2/27 suspension resulted in the reduction of symptoms caused by P21 on sugar beet. T6SS led to the upregulation of npr1 and nced genes in plants' local immune response. This upregulation wasn’t observed in plants' systemic immune response. Overall, the pathogenic potential of P. syringae pv. aptata is mediated by the diversity of genes and secreted effectors involved in virulence. P. putida S2/27 has the potential for application in its biocontrol

Pseudomonas syringae pv. aptata, genom, sekretom, T3SS, Pseudomonas putida, biološka kontrola, T6SS

Pseudomonas syringae pv. aptata, genome, secretome, T3SS, Pseudomonas putida, biological control, T6SS

579.25:579.64(043.3)

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