History of Physiological Plant Pathology

Fuchs, W. H.

doi:10.1007/978-3-642-66279-9_1

Cited by 6 publications

(4 citation statements)

References 78 publications

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“…Obligate biotrophic fungi, however, manage to maintain host cell viability for extended periods, and serve as a sink for plant metabolites. This special relationship between highly specialized fungal hyphae and host cells, tissue or organs has been called the 'aegricorpus' (Fuchs, 1976). Typical examples include the powdery mildews (Aist & Bushnell, 1991), rusts (Bushnell, 1984) and downy mildew fungi (Hohl, 1991).…”

Section: Introductionmentioning

confidence: 99%

Infection structures of fungal plant pathogens – a cytological and physiological evaluation

1993

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SUMMARY Many fungi differentiate specific infection structures in order to infect the host plant. The spore attaches to the host surface, the cuticle, and the germ tube may recognize suitable penetration sites, over which an appressorium is formed. Additional wall layers in appressoria of many fungi suggest that this structure supports increasing pressure during the penetration process. During appressorium formation, synthesis of polymer‐degrading enzymes is often initiated. Cutinases, cellulases and pectin‐degrading enzymes can be formed in a developmentally controlled or adaptive, i.e. substrate‐dependent, fashion. The penetration hypha develops below the appressorium. This hypha has a new wall structure and exhibits features which serve to breach the plant cell wall. However, at present it is not clear whether penetration hyphae arising from appressoria are more efficient in penetration or induce less damage than hyphae which penetrate without detectable special adaptations. The infection hypha differentiates within the host. During differentiation a characteristic set of enzymes is synthesized to enable successful establishment of the host‐pathogen relationship. If, as in most cases, multiple forms of cell wall‐degrading enzymes are formed by the pathogen, mutagenesis or deletion of a gene encoding one of these enzymes very often has no effect on pathogenicity or even virulence. Proof is missing very often that an enzyme is needed at the right time and at the right site of infection. Events occurring during differentiation of fungal infection structures are reviewed with special emphasis on Magnaporthe grisea, Colletotrichum spp., and rust fungi, and common features which may be of importance to the success of infection are discussed.

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Section: Introductionmentioning

confidence: 99%

Infection structures of fungal plant pathogens – a cytological and physiological evaluation

1993

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“…The opine degradative pathways are encoded on the Ti plasmids but at locations separate from the transferred regions (for reviews, see references 18, 20, 27, 31, 33, 38, and 44). Since crown gall cells are genetically modified by the bacterium to redirect their metabolic activities toward the production of nutrients specific for the pathogen, A. tumefaciens represents an interesting example of biotrophic parasitism in which the pathogen obtains its nutrients from the living cell of its host (17 (16,21) and Agrobacterium rhizogenesinduced hairy root proliferations (28) and the observation that some opines induce the conjugative transfer of Ti plasmids have given a broad basis to this concept (12,22,23,31). The question as to whether similar nutritional relationships exist in other plant-bacterial interactions was answered when a new substance (41), 3-O-methyl-scylloinosamine, was identified in alfalfa nodules incited by a particular Rhizobium meliloti strain.…”

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confidence: 99%

Opine utilization by Agrobacterium spp.: octopine-type Ti plasmids encode two pathways for mannopinic acid degradation

et al. 1988

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Octopine-type strains of Agrobacterium tumefaciens degrade the opine mannopinic acid through a specific pathway which involves cleavage of the molecule at the C-N bond between the amino acid and the sugar moieties. Mannose was identified as a product of the reaction. This pathway was inducible by mannopinic and agropinic acids, but not by mannopine or agropine, the two other mannityl opines. The transport system for this pathway appeared to be specific for mannopinic acid. A second, nonspecific pathway for mannopinic acid degradation was also identified. This involved some of the catabolic functions associated with the metabolism of mannopine and agropine. This second pathway was inducible by mannopine and agropine but not by mannopinic or agropinic acids. The transport system for this pathway appeared to have a broad specificity.Transposon TnS insertion mutants affected in the specific catabolic pathway were isolated and analyzed. These mutants continued to catabolize mannopine and agropine. Both mapped to a region of the Ti plasmid previously shown to be associated with the catabolism of mannopinic acid. Restriction enzyme analysis of the Ti plasmid from strain 89.10, an octopine strain that is naturally unable to utilize mannopinic acid, showed a deletion in this same region encoding the specific mannopinic acid degradation pathway. Analysis of recombinant clones showed that the second, nonspecific pathway was encoded in a region of the Ti plasmid associated with mannopine and agropine catabolism. This region shared no structural overlap with the segment of the plasmid encoding the specific mannopinic acid degradative pathway.Opines are specific compounds that are synthesized by crown gall tumors elicited by Agrobacterium tumefaciens. Pathogenicity in this bacterium is associated with a highmolecular-weight plasmid, called the Ti (tumor-inducing) plasmid, a segment of which, the T-DNA (transferred DNA) is integrated into and expressed by the transformed plant cells. T-DNA expression determines the phenotype of the tumor cells, including opine production (for reviews, see references 18, 20, 27, 33, and 44). Some 20 different opines that belong to several structural groups have been identified (3,4,6,13,16,21; for reviews, see references 30 and 38). All opines are not present in any given tumor. The classes of opines synthesized depend on the particular Ti plasmid harbored by the inciting Agrobacterium strain (6, 13, 16, of the plant metabolites on which pathogens feed, and the concept that specific growth substrates can be produced by host cells has not been studied much. In the case of Agrobacterium spp., this concept (36, 40) appears be generally applicable. Indeed, the discovery of several new opines in crown gall tumors (16,21) and Agrobacterium rhizogenesinduced hairy root proliferations (28) and the observation that some opines induce the conjugative transfer of Ti plasmids have given a broad basis to this concept (12,22,23,31). The question as to whether similar nutritional relationships exist in othe...

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“…[23][24][25][26][27]). There is, however, a great diversity in the reactions of microorganisms to phenolics: some organisms may even be stimulated by certain phenolics or are able to metabolise them [28,29]. Oxidized and polymerized products of phenolic compounds are of varying toxicity.…”

Section: Role Of Polyphenolics In Disease Resistancementioning

confidence: 99%

The susceptibility of plants to Agrobacterium: A discussion of the role of phenolic compounds

Cleene¹

1988

FEMS Microbiology Letters

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History of Physiological Plant Pathology

Cited by 6 publications

References 78 publications

Infection structures of fungal plant pathogens – a cytological and physiological evaluation

Infection structures of fungal plant pathogens – a cytological and physiological evaluation

Opine utilization by Agrobacterium spp.: octopine-type Ti plasmids encode two pathways for mannopinic acid degradation

The susceptibility of plants to Agrobacterium: A discussion of the role of phenolic compounds

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