Histological and molecular studies of the non-host interaction between wheat and Uromyces fabae

Abstract

Non-host resistance (NHR) confers plant species immunity against the majority of microbes. As an important crop, wheat can be damaged by several Puccinia species but is immune to all Uromyces species. Here, we studied the basis of NHR in wheat against the broad bean rust pathogen Uromyces fabae (Uf). In the wheat-Uf interaction, microscopic observations showed that urediospores germinated efficiently on wheat leaves. However, over 98% of the germ tubes failed to form appressoria over stomata. For the few that invaded through stomata, the majority of them failed to penetrate wheat mesophyll cells. At 96 hours after inoculation, less than 4% of the Uf infection units that had entered the mesophyll tissue formed haustoria. Attempted penetration by haustorium mother cells induced the thickening of cell wall and the formation of papillae in plant cells, which arrested the development or growth of Uf penetration pegs. For the Uf haustoria formed in wheat cells, they were encased in callose-like materials and did not elicit hypersensitive response. Localized accumulation of H(2)O(2) were observed in plant cell walls, papillae and encasement of haustoria during the wheat-Uf interaction. Furthermore, quantitative RT-PCR analysis showed that several genes involved in basal resistance and oxidative stress responses were up-regulated during Uf infection. In conclusion, our study revealed the cytological and molecular bases of NHR in wheat against the non-adapted rust fungus Uf, and highlighted the significance of papilla production in the prehaustorial NHR.

Cytological and molecular analysis of nonhost resistance in rice to wheat powdery mildew and leaf rust pathogens

“…Attempted infection by Bgt and Ptr induced several strong defense responses in rice epidermal cells and mesophyll cells, respectively, including callose deposition, ROS accumulation, and posthaustorial HR with cell death at the cytological level. These defense responses were also frequently observed in other nonhost interactions involving powdery mildew or rust fungi (Cheng et al 2012;Heath 1974;Huckelhoven et al 2001;Yun et al 2003;Zhang et al 2011). Therefore, these defense responses are considered general NHR responses against all Fig.…”

The Plasmodesmal Protein PDLP1 Localises to Haustoria-Associated Membranes during Downy Mildew Infection and Regulates Callose Deposition

“…The encasement of haustoria by host cells has been observed in both compatible and incompatible interactions and can allow the host to suppress the growth of the pathogen [2], [9], [70], [71]. A variety of materials are deposited in haustorial encasements, including polysaccharides, proteins and membranous material, forming a barrier that is presumed to inhibit the loss of nutrients from the host and effector delivery from the pathogen.…”

Characterization and Genetic Analysis of Rice Mutant crr1 Exhibiting Compromised Non-host Resistance to Puccinia striiformis f. sp. tritici (Pst)

“…Pst isolate CYR32 (a predominant Pst race in China) were maintained on a susceptible wheat cultivar, Mingxian 169, following the procedures and conditions described by Zhang et al (2011). For inoculation of rice, 3-week-old rice seedlings were pre-spayed with 0.1% Triton X-100, then fresh Pst urediniospores suspensions (50 mg urediniospores ml -1 ) were applied with a fine paintbrush onto the adaxial surface of the second leaf.…”

“…The specimens were cleared in saturated chloral hydrate until leaf tissues were translucent. For Calcofluor White (Sigma–Aldrich) staining, the method described by Zhang et al (2011) was followed. For further visualization of internal infection structures, the wheat germ agglutinin (WGA) conjugated to the Fluorophore Alexa 488 (Invitrogen) staining was used (Ayliffe et al, 2011b).…”

“…Leaves were harvested from inoculated rice crr1 mutants at 2-week after inoculation and prepared for transmission electron microscope (TEM) examination according to procedures previously described (Zhang et al, 2011). The leaf samples were cut into small pieces and fixed with 3% (v/v) glutaraldehyde in 50 mmol/l phosphate buffer (pH 6.8) for 3–6 h at 4°C.…”