Insight into Types I and II nonhost resistance using expression patterns of defense-related genes in tobacco

Abstract

Plants protect themselves against pathogens using a range of response mechanisms. There are two categories of nonhost resistance: Type I, which does not result in visible cell death; and Type II, which entails localized programmed cell death (or hypersensitive response) in response to nonhost pathogens. The genes responsible for these two systems have not yet been intensively investigated at the molecular level. Using tobacco plants (Nicotiana tabacum), we compared expression of 12 defense-related genes between a Type I (Xanthomonas axonopodis pv. glycines 8ra) nonhost interaction, and two Type II (Pseudomonas syringae pv. syringae 61 and P. syringae pv. phaseolicola NPS3121) nonhost interactions, as well as those expressed during R gene-mediated resistance to Tobacco mosaic virus. In general, expression of most defense-related genes during R gene-mediated resistance was activated 48 h after challenge by TMV; the same genes were upregulated as early as 9 h after infiltration by nonhost pathogens. Surprisingly, X. axonopodis pv. glycines (Type I) elicited the same set of defense-related genes as did two pathovars of P. syringae, despite the absence of visible cell death. In two examples of Type II nonhost interactions, P. syringae pv. phaseolicola NPS3121 produced an expression profile more closely resembling that of X. axonopodis pv. glycines 8ra, than that of P. syringae pv. syringae 61. These results suggest that Type I nonhost resistance may act as a mechanism providing a more specific and active defense response against a broad range of potential pathogens.

VIGS-Mediated Forward Genetics Screening for Identification of Genes Involved in Nonhost Resistance

“…One, identification of silenced plants susceptible to nonhost pathogen by GFPuv-based assay increases the accuracy as in planta growth can be viewed. Second, this method allows identification of genes involved in both type-I nonhost resistance 2,26 (does not result in visible cell death) and type-II nonhost resistance 2,26 (results in hypersensitive response cell death). For example, we previously identified a clone called 6C8 and the silenced plants were susceptible to both type-1 and type-2 pathogens 18 .…”

Resistance to viruses of potato: current status and prospects

“…Гены растения, отвечающие за первоначальный защитный ответ, сходным образом экспрессируются и при NHR типа II, и при специфиче ской устойчивости в растениях табака (Oh et al, 2006), свидетельствуя о том, что сигнальные пути этих защитных систем перекрываются. NHR против патогенов отдален но родственных хозяев обычно включает комплексные, многослойные, количественно наследуемые механизмы.…”

Olive – Colletotrichum acutatum: An Example of Fruit-Fungal Interaction

“…On the other hand, a compatible interaction is when plant disease occurs, due to an inadequate defence response of the host against the pathogen in terms of timing and intensity (Casado Díaz et al, 2006;Mysore & Ryu, 2004). In many plant species one of the most typical symptoms of defence response is the rapid plant cell death at the infection site, the hypersensitive response (HR), which limits pathogen from spreading to other cells (Dangl et al, 1996;Glazebrook, 2005;Oh et al, 2006). Van Der Plank (1966) reported two categories of disease resistance in plants: vertical and horizontal resistance.…”

“…In the review work Mysore & Ryu (2004) proposed that non-host resistance against bacteria, fungi, and oomycetes can be also classified into: (i) type I, which does not result in visible cell death and (ii) type II, in which a hypersensitive response occurs, resulting in cell death at the infection site. The host resistance has been studied intensively in different pathosystem, while non-host resistance remains poorly understood (Oh et al, 2006). However, many aspects related to the gene expression patterns in some host-pathogen interaction have not yet been cleared.…”