Sr36- and Sr5-Mediated Resistance Response to Puccinia graminis f. sp. tritici Is Associated with Callose Deposition in Wheat Guard Cells

Abstract

Race-specific resistance of wheat to Puccinia graminis f. sp. tritici is primarily posthaustorial and often involves the induction of a hypersensitive response (HR). The aim of this study was to investigate host defense responses induced in interactions between P. graminis f. sp. tritici races and wheat lines carrying different race-specific stem rust resistance (Sr) genes. In incompatible interactions between wheat lines carrying Sr36 in three genetic backgrounds (LMPG, Prelude, or W2691) and avirulent P. graminis f. sp. tritici races MCCFC or RCCDM, callose accumulated within 24 h in wheat guard cells contacted by a P. graminis f. sp. tritici appressorium, and P. graminis f. sp. tritici ingress was inhibited following appressorium formation. Accordingly, the expression of transcripts encoding a callose synthase increased in the incompatible interaction between LMPG-Sr36 and avirulent P. graminis f. sp. tritici race MCCFC. Furthermore, the inhibition of callose synthesis through the infiltration of 2-deoxy-D-glucose (DDG) increased the ability of P. graminis f. sp. tritici race MCCFC to infect LMPG-Sr36. A similar induction of callose deposition in wheat guard cells was also observed within 24 h after inoculation (hai) with avirulent P. graminis f. sp. tritici race HKCJC on LMPG-Sr5 plants. In contrast, this defense response was not induced in incompatible interactions involving Sr6, Sr24, or Sr30. Instead, the induction of an HR and cellular lignification were noted. The manifestation of the HR and cellular lignification was induced earlier (24 hai) and was more extensive in the resistance response mediated by Sr6 compared with those mediated by Sr24 or Sr30. These results indicate that the resistance mediated by Sr36 is similar to that mediated by Sr5 but different from those triggered by Sr6, Sr24, or Sr30. Resistance responses mediated by Sr5 and Sr36 are prehaustorial, and are a result of very rapid recognition of molecules derived from avirulent isolates of P. graminis f. sp. tritici, in contrast to the responses triggered in lines with Sr6, Sr24, and Sr30.

Histopathological aspects of induced resistance byPseudomonas protegensCHA0 and β-aminobutyric acid in wheat againstPuccinia triticina

“…Our results showed that callose depositions were mainly detected in guard cells. In support of our observations, Wang et al (2015) demonstrated that the resistance response to Puccinia graminis f. sp. tritici is associated with callose deposition in the wheat guard cells.…”

High throughput transcriptome analysis of coffee reveals prehaustorial resistance in response to Hemileia vastatrix infection

“…tritici pathosystem, during this interaction the resistance gene RPG1 was expressed a few minutes after inoculation with stem rust races (Nirmala et al 2010). More recently, in the same pathosystem it was observed early responses to avirulent stem rust races in wheat carrying resistance genes Sr5 and Sr36 involved callose deposition in stomatal guard cells (Wang et al 2015). It is possible that the genes identified here as induced in early hours in HdT may trigger a rapid and efficient response for the plant defense, and these mechanisms may involve pre-haustorial resistance in coffee-H. vastatrix interaction, in the same way found for barley and wheat pre-haustorial defense to P. graminis.…”

Cellular and molecular characterization of a stem rust resistance locus on wheat chromosome 7AL

“…HR is reported to usually involve the death of host mesophyll cells, after the development of haustoria [19]; however, others have also observed pre-haustorial resistance responses in incompatible, ETI-mediated interactions. For example, a pre-haustorial response to stem rust was recently reported by Wang et al [20], who observed that early responses to avirulent stem rust races in wheat carrying resistance genes Sr5 and Sr36 involved callose deposition in stomatal guard cells. Another notable example of a pre-haustorial response to wheat stem rust is the case of barley durable stem rust resistance gene Rpg1 , which encodes a receptor-like kinase (RLK) that is autophosphorylated within minutes of inoculation with the avirulent pathogen [21, 22].…”