Potato genotypes differentially alter the expression of Phytophthora infestans effectors during PAMP-mediated resistance induction (original) (raw)
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Plant Pathology, 2008
Defence responses were investigated in two potato cultivars with different levels of resistance to late blight, Russet Burbank (susceptible) and Kennebec (moderately resistant), after inoculation with single isolates representing Phytophthora infestans genotypes US-1 (previously predominant, mildly aggressive) and US-8 (currently predominant, highly aggressive). The accumulation of brown lignin-like materials and an increase in the cell wall affinity to trypan blue 24 h after inoculation were observed in cv. Kennebec inoculated with US-1, but not in Kennebec inoculated with US-8, or cv. Russet Burbank inoculated with either US-1 or US-8. The expression of PAL-1, HMG-2, PR-1 and PR-5 was investigated in three leaf strata (local, proximal and distal) and at different times after inoculation, using SYBR real-time RT-PCR. The activation of these defence-related genes was affected not only by P. infestans genotype, but also by the potato cultivar and the proximity to the inoculation site. These genes were up-regulated earlier in Kennebec than in Russet Burbank and in response to US-1 than to US-8. Over all, the earliest and strongest up-regulation of these genes occurred in Kennebec inoculated with US-1. Furthermore, PAL-1 and HMG-2 were down-regulated at the site of infection while such downregulation was not observed for PR-1 or PR-5 . In parallel, the accumulation level and location of phenolics and rishitin matched those of PAL-1 and HMG-2 transcripts, respectively. These results strongly suggest that changes in either the activation or suppression of defence responses by the pathogen shape the level of susceptibility of potato cultivars to late blight.
Plant Pathology, 2015
Quantitative resistance may depend on the effectiveness of PAMP-triggered immunity. This study highlights the diversity of mechanisms involved in the quantitative resistance of potato to Phytophthora infestans. The investigation focused on the implication of the hormone signalling pathways induced in four potato genotypes by a concentrated culture filtrate (CCF) of P. infestans. The genotypes were ranked according to their level of resistance to P. infestans and discriminant analysis of gene expression profiles separated the most resistant genotype from the three others, particularly because of a strong induction of the salicylic acid (SA) pathway. In this genotype, transcripts involved in the SA pathway, EDS1, WRKY1, PR-1 and PR-2, were induced by CCF. SA pathway involvement was confirmed by a peak of SA accumulation 12 h after elicitation and by the induction of jaz1 (jasmonate Zim domain protein 1) transcripts, which inhibit defence responses mediated by jasmonic acid (JA). By contrast, neither a significant induction of SA-mediated responses nor an accumulation of free SA and PR-2 were observed in the other resistant or two susceptible cultivars. Expression of genes in the ET and JA pathways was either not, or weakly, induced by CCF in potato. Finally, the involvement of signalling pathways was genotype dependent rather than correlating with resistance level.
Horticulture research, 2022
Most potato cultivars are susceptible to late blight disease caused by the oomycete pathogen Phytophthora infestans. Here we report that the genetic loss of host susceptibility is a new source of resistance to prevent or diminish pathogen infection. Previously, we showed that RNAi-mediated silencing of the potato susceptibility (S) genes StDND1, StDMR1, and StDMR6 leads to increased late blight resistance. The mechanisms underlying this S-gene-mediated resistance have thus far not been identified. In this study, we examined the infection process of P. infestans in StDND1-, StDMR1-, and StDMR6-silenced potato lines. Microscopic analysis showed that penetration of P. infestans spores was hampered in StDND1-silenced plants. In StDMR1-and StDMR6-silenced plants, P. infestans infection was arrested at a primary infection stage by enhanced cell death responses. Histochemical staining revealed that StDMR1and StDMR6-silenced plants display elevated ROS levels in cells at the infection sites. Resistance in StDND1-silenced plants, however, seems not to rely on a cell death response as ROS accumulation was found to be absent at most inoculated sites. Quantitative analysis of marker gene expression suggests that the increased resistance observed in StDND1-and StDMR6-silenced plants relies on an early onset of salicylic acid-and ethylene-mediated signaling pathways. Resistance mediated by silencing StDMR1 was found to be correlated with the early induction of salicylic acid-mediated signaling. These data provide evidence that different defense mechanisms are involved in late blight resistance mediated by functional impairment of different potato S-genes.
Molecular plant-microbe interactions : MPMI, 2018
Phytophthora infestans causes the devastating potato late blight disease which is widely controlled with fungicides. However, the debate of chemical control is fueling a promotion towards alternative methods. In this context, the enhancement of natural plant immunity could be a strategy for more sustainable protection. We previously demonstrated that a Concentrated Culture Filtrate (CCF) of P.infestans primes defense reactions in potato. They are genotype-dependent, and metabolites produced decrease pathogen growth in vitro but not in vivo on tubers. Induced potato defenses are assumed to affect P.infestans life-history traits depending on strains. This assumption was studied in vivo through induced leaflets on a susceptible genotype inoculated with four P.infestans strains differing for lesion growth rate. This study combines both defenses mechanistic analysis and ecological observations. Defense genes expressions were thus assessed by qRT-PCR; pathogen development was simultaneous...
Frontiers in Plant Science, 2020
Late blight is considered the most renowned devastating potato disease worldwide. Resistance gene (R)-based resistance to late blight is the most effective method to inhibit infection by the causal agent Phytophthora infestans. However, the limited availability of resistant potato varieties and the rapid loss of R resistance, caused by P. infestans virulence variability, make disease control rely on fungicide application. We employed an Agrobacterium tumefaciens-mediated transient gene expression assay and effector biology approach to understand late blight resistance of Chinese varieties that showed years of promising field performance. We are particularly interested in PiAvr3a EM , the most common virulent allele of PiAvr3a KI that triggers a R3a-mediated hypersensitive response (HR) and late blight resistance. Through our significantly improved A. tumefaciensmediated transient gene expression assay in potato using cultured seedlings, we characterized two dominant potato varieties, Qingshu9 and Longshu7, in China by transient expression of P. infestans effector genes. Transient expression of 10 known avirulence genes showed that PiAvr4 and PiAvr8 (PiAvrsmira2) could induce HR in Qingshu9, and PiAvrvnt1.1 in Longshu7, respectively. Our study also indicated that PiAvr3a EM is recognized by these two potato varieties, and is likely involved in their significant field performance of late blight resistance. The identification of natural resistance mediated by PiAvr3a EM recognition in Qingshu9 and Longshu7 will facilitate breeding for improved potato resistance against P. infestans.
Plant Cell Reports, 2012
Sarpo Mira, a potato variety with high resistance against the late blight pathogen Phytophthora infestans, is being used in breeding programs to increase late blight resistance in commercial varieties. Discovering genes that are important for P. infestans resistance will assist in the development of molecular markers for the selection of new resistant cultivars and the use of resistant varieties will reduce the environmental, health and financial costs associated with the use of pesticides. Using complementary DNA amplified fragment length polymorphism analyses, differentially expressed genes involved in the potato-P. infestans interaction were identified in the susceptible Bintje and in the resistant Sarpo Mira potato cultivars. Forty-eight differentially expressed transcript derived fragments (TDFs) were cloned and sequenced. The expression profiles of some of these genes were analyzed in detail using quantitative RT-PCR at seven time points: 1, 4, 17, 24, 30, 41 and 65 hours after inoculation (hai). We found that five transcripts with homologies to pathogenesis/defense-related genes and two TDFs with homology to transcription factors were significantly induced to higher levels in the resistant cultivar at very early stages of the infection (1 hai). Interestingly, most of these genes showed different expression profiles throughout the whole infection process between both cultivars. Particularly during its biotrophic growth phase, P. infestans triggered the down-regulation of infection responsive genes in the susceptible but not in the resistance cultivar. Our results suggest that these newly identified early-induced transcripts may be good candidates for conferring Sarpo Mira's resistance to late blight and they could be useful molecular markers for the selection of new resistant cultivars.
Plant Molecular Biology, 2001
To find out more about the interaction between potato and Phytophthora infestans at the molecular level, we screened for genes induced early after infection using mRNA differential display. Among the twenty cDNA clones recovered in the screen, two were found to represent plant genes whose transcript levels increased during infection of intact plants. These two genes differed strikingly in their response to wounding. Stprx2, a putative peroxidase, responded slowly and transiently to wounding, and its expression pattern was similar to that of gst1, a well-described pathogen-induced gene of potato. The second gene, StNAC, was induced rapidly and strongly after wounding but not systemically. Transcript levels reached a maximum after around 1 h and returned to basal levels after ca. 24 h. StNAC has strong similarity to the ATAF subfamily of NAC domain proteins, a large family of putative transcriptional activators. Arabidopsis ATAF1 and ATAF2 were also shown to be induced by wounding. This implies that the ATAF genes are not merely structurally similar but also share a conserved role in stress responses.
PLoS ONE, 2011
While the mechanisms underlying quantitative resistance of plants to pathogens are still not fully elucidated, the Pathogen-Associated Molecular Patterns (PAMPs)-triggered response model suggests that such resistance depends on a dynamic interplay between the plant and the pathogen. In this model, the pathogens themselves or elicitors they produce would induce general defense pathways, which in turn limit pathogen growth and host colonisation. It therefore suggests that quantitative resistance is directly linked to a common set of general host defense mechanisms, but experimental evidence is still inconclusive. We tested the PAMP-triggered model using two pathogens (Pectobacterium atrosepticum and Phytophthora infestans) differing by their infectious processes and five potato cultivars spanning a range of resistance levels to each pathogen. Phenylalanine ammonia-lyase (PAL) activity, used as a defense marker, and accumulation of phenolics were measured in tuber slices challenged with lipopolysaccharides from P. atrosepticum or a concentrated culture filtrate from P. infestans. PAL activity increased following treatment with the filtrate but not with lipopolysaccharides, and varied among cultivars. It was positively related to tuber resistance to P. atrosepticum, but negatively related to tuber resistance to P. infestans. It was also positively related to the accumulation of total phenolics. Chlorogenic acid, the main phenolic accumulated, inhibited growth of both pathogens in vitro, showing that PAL induction caused active defense against each of them. Tuber slices in which PAL activity had been induced before inoculation showed increased resistance to P. atrosepticum, but not to P. infestans. Our results show that inducing a general defense mechanism does not necessarily result in quantitative resistance. As such, they invalidate the hypothesis that the PAMP-triggered model alone can explain quantitative resistance. We thus designed a more complex model integrating physiological host response and a key pathogen life history trait, pathogen growth, to explain the differences between the two pathosystems.
Paranoid potato: Phytophthora-resistant genotype shows constitutively activated defense
Plant Signaling & Behavior, 2012
Phytophthora is the most devastating pathogen of dicot plants. There is a need for resistance sources with different modes of action to counteract the fast evolution of this pathogen. In order to better understand mechanisms of defense against P. infestans, we analyzed several clones of potato. Two of the genotypes tested, Sarpo Mira and SW93-1015, exhibited strong resistance against P. infestans in field trials, whole plant assays and detached leaf assays. The resistant genotypes developed different sizes of hypersensitive response (HR)-related lesions. HR lesions in SW93-1015 were restricted to very small areas, whereas those in Sarpo Mira were similar to those in Solanum demissum, the main source of classical resistance genes. SW93-1015 can be characterized as a cpr (constitutive expressor of PR genes) genotype without spontaneous microscopic or macroscopic HR lesions. This is indicated by constitutive hydrogen peroxide (H 2 O 2 ) production and PR1 (pathogenesis-related protein 1) secretion. SW93-1015 is one of the first plants identified as having classical protein-based induced defense expressed constitutively without any obvious metabolic costs or spontaneous cell death lesions.