Incompatibility Reaction Research Articles

Histological characterization of root-knot nematode resistance in cowpea and its relation to reactive oxygen species modulation

Root-knot nematodes (Meloidogyne spp.) are sedentary endoparasites with a broad host range which includes economically important crop species. Cowpea (Vigna unguiculata L. Walp) is an important food and fodder legume grown in many regions where root-knot nematodes are a major problem in production fields. Several sources of resistance to root-knot nematode have been identified in cowpea, including the widely used Rk gene. As part of a study to elucidate the mechanism of Rk-mediated resistance, the histological response to avirulent M. incognita feeding of a resistant cowpea cultivar CB46 was compared with a susceptible near-isogenic line (in CB46 background). Most root-knot nematode resistance mechanisms in host plants that have been examined induced a hypersensitive response (HR). However, there was no typical HR in resistant cowpea roots and nematodes were able to develop normal feeding sites similar to those in susceptible roots up to 9-14 d post inoculation (dpi). From 14-21 dpi giant cell deterioration was observed and the female nematodes showed arrested development and deterioration. Nematodes failed to reach maturity and did not initiate egg laying in resistant roots. These results confirmed that the induction of resistance is relatively late in this system. Typically in pathogen resistance HR is closely associated with an oxidative burst (OB) in infected tissue. The level of reactive oxygen species release in both compatible and incompatible reactions during early and late stages of infection was also quantified. Following a basal OB during early infection in both susceptible and resistant roots, which was also observed in mechanically wounded root tissues, no significant OB was detected up to 14 dpi, a profile consistent with the histological observations of a delayed resistance response. These results will be useful to design gene expression experiments to dissect Rk-mediated resistance at the molecular level.

Molecular characterization of cell death induced by a compatible interaction between Fusarium oxysporum f. sp. linii and flax (Linum usitatissimum) cells

The cellular and molecular events associated with cell death during compatible interaction between Fusarium oxysporum sp. linii and a susceptible flax (Linum usitatissimum) cell suspension are reported here. In order to determine the physiological and molecular sequence of cell death of inoculated cells, reactive oxygen species (ROS) production, mitochondrial potential, lipoxygenase, DNase, protease and caspase-3-like activities, lipid peroxidation and secondary metabolite production were monitored. We also used microscopy, in situ terminal deoxynucleotidyl transferase-mediated dUTP nick end labelling (TUNEL) and DNA fragmentation assay. Cell death was associated with specific morphological and biochemical changes that are generally noticed in hypersensitive (incompatible) reaction. An oxidative burst as well as a loss of mitochondrial potential of inoculated cells, an activation of lipoxygenase and lipid peroxidation were noted. Enzyme-mediated nuclear DNA degradation was detectable but oligonucleosomal fragmentation was not observed. Caspase-3-like activity was dramatically increased in inoculated cells. Phenylpropanoid metabolism was also affected as demonstrated by activation of PAL and PCBER gene expressions and reduced soluble lignan and neolignan contents. These results obtained in flax suggest that compatible interaction triggers a cell death sequence sharing a number of common features with the hypersensitive response observed in incompatible interaction and in animal apoptosis.

The Role of Reproductive Assurance in the Arctic: a Comparative Study of a Homostylous and Distylous Species Pair

ABSTRACTPollinator-dependent reproductive systems are predicted to be disadvantageous in the Arctic due to the unreliability of pollinator services. Observations in northwestern Alaska appear to support this prediction, where the common Primula eximia possesses reproductive assurance through homostyly and is outpacing the reproduction of its rare, distylous, and pollinator-dependent congener, P. tschuktschorum. We examined the reproductive ecology of these two taxa to determine if P. tschuktschorum is fully distylous with self and intramorph incompatibility, if P. eximia is homostylous with an advantage in fecundity over the rare species, and if there are reproductive interactions between the species. Our results indicate that while P. tschuktschorum is morphologically distylous, it displays only weak incompatibility reactions, but nonetheless has significant reproductive limitations relative to the fecundity of P. eximia, especially in the face of herbivory, which reduces the pool of compatible mates. Some hybridization is occurring between the species. These results support previous suggestions that reproductive assurance may be an important factor limiting the distribution of distyly where pollinator service is unreliable. Homostylous species are likely to be more successful and outcompete distylous progenitors, and selection pressures for reproductive assurance may lessen strong self and intramorph incompatibility reactions in distylous species.

Drug incompatibility reaction with use of fluorescein during anaesthesia

Drug incompatibility reaction with use of fluorescein during anaesthesia

The effect of compression forces on the stability of dibasic calcium phosphate dihydrate tablets in the presence of glutamic acid hydrochloride monitored by isothermal calorimetry

Dibasic calcium phosphate dihydrate (DCPD) has been widely used as tablet diluent in both wet granulation and direct compression. Although DCPD is considered as a stable and inert diluent, it has been reported that certain acetic drugs and humidity/temperature conditions can evoke the loss of crystalline water. This study investigates the ability of isothermal calorimetry to detect any incompatibility reaction between glutamic acid hydrochloride (GAHCL), as an acidic model drug, and DCPD. The study identified an exothermic and endothermic reaction between GAHCL and DCPD which are influenced by compression forces. A correlation between the tablet relaxation energy and the magnitude of the solid state reaction between GAHCL and DCPD was established.

The progamic phase and seed formation in Armoracia rusticana

AbstractThe progamic phase is a period of specific interaction between the male gametophyte and the pistil tissues and is very important for proper seed development in plants. The aims of this study were to investigate the events during the progamic phase in Armoracia rusticana, to examine a plant’s capability of sexual reproduction and to obtain vital seeds under natural conditions. There were very few pollen grains on the stigmas at anthesis stage. The incompatibility reaction between the stigma cells and pollen grains was observed by using fluorescence microscopy. A series of ovary cross‐sections revealed a high accumulation of Periodic Acid Schiff (PAS)‐positive globules in all the embryo sacs. About 33% of ovules in the ovary were fertilized, but only 3% of them were able to germinate into seedlings.

Cloning of a putative hypersensitive induced reaction gene from wheat infected by stripe rust fungus

The hypersensitive response (HR) is one of the most efficient forms of plant defense against biotrophic pathogens and results in localized cell death and the formation of necrotic lesions. In this study, a novel putative hypersensitive induced reaction (HIR) gene from wheat leaves infected by incompatible stripe rust pathogen CY23, designated as Ta-hir1, was identified by using rapid amplification of cDNA ends (RACE). Ta-hir1 encodes 284 amino acids, with a predicted molecular mass of 31.31 KDa. A phylogenetic analysis showed that Ta-hir1 was highly homologous to Hv-hir1 from barley at both cDNA and deduced amino-acid levels. Amino-acid sequence analysis of the wheat HIR protein indicated the presence of the SPFH (Stomatins, Prohibitins, Flotillins and HflK/C) protein domain typical for stomatins which served as a negative regulator of univalent cation permeability, especially for potassium. The expression profile of the Ta-hir1 transcript detected by reverse transcriptase-polymerase chain reaction (RT-PCR) and real-time polymerase chain reaction (real time-PCR), respectively, showed that the highest expression occurred 48 h post inoculation (hpi), which is consistent with our previous histopathology observations during the stripe rust fungus–wheat incompatible reaction.

Association between vegetative compatibility and aflatoxin production by Aspergillus species during intraspecific competition

Intraspecific competition is the basis for biological control of aflatoxins, but there is little understanding of the mechanism(s) by which competing strains inhibit toxin production. Evidence is presented that demonstrates a relationship between strength of the vegetative compatibility reaction and aflatoxin production in Aspergillus flavus and A. parasiticus using the suspended disk culture method. Combining wild-type aflatoxin-producing isolates belonging to different vegetative compatibility groups (VCGs) resulted in a substantial reduction in aflatoxin yield. Pairs of aflatoxin-producing isolates within the same VCG, but showing weak compatibility reactions using complementary nitrate-nonutilizing mutants, also were associated with reduced levels of aflatoxin B1. In contrast, pairings of isolates displaying a strong compatibility reaction typically produced high levels of aflatoxins. These results suggest that interactions between vegetatively compatible wild-type isolates of A. flavus and A. parasiticus are cooperative and result in more aflatoxin B1 than pairings between isolates that are incompatible. Successful hyphal fusions among spore germlings produce a common mycelial network with a larger resource base to support aflatoxin biosynthesis. By comparison, vegetative incompatibility reactions might result in the death of those heterokaryotic cells composed of incompatible nuclei and thereby disrupt the formation of mycelial networks at the expense of aflatoxin biosynthesis.

Temporal Gene Expression Profiling of the Wheat Leaf Rust Pathosystem Using cDNA Microarray Reveals Differences in Compatible and Incompatible Defence Pathways

In this study, we detail the construction of a custom cDNA spotted microarray containing 7728 wheat ESTs and the use of the array to identify host genes that are differentially expressed upon challenges with leaf rust fungal pathogens. Wheat cultivar RL6003 (Thatcher Lr1) was inoculated with Puccinia triticina virulence phenotypes BBB (incompatible) or TJB (7-2) (compatible) and sampled at four different time points (3, 6, 12, and 24 hours) after inoculation. Transcript expression levels relative to a mock treatment were measured. One hundred ninety two genes were found to have significantly altered expression between the compatible and incompatible reactions. Among those were genes involved in photosynthesis, the production of reactive oxygen species, ubiquitination, signal transduction, as well as in the shikimate/phenylpropanoid pathway. These data indicate that various metabolic pathways are affected, some of which might be used by RL6003 to mount a coordinated defense against an incompatible fungal pathogen.

Histological Evaluation of Early Graft Compatibility in Uapaca kirkiana Müell Arg. Scion/Stock Combinations

Compatibility of scion and stock combinations in Uapaca kirkiana fruit trees has not been evaluated despite noticeable growth irregularities. The objectives of this study were to determine graft compatibility of scion/stock combinations and possible causes of graft incompatibility. Scion, stock, and graft union diameters were measured. Stem sections comprising the graft unions were immersed in formalin acetic acid and then washed in sterile water. These were transversely dissected across the unions and examined under using light microscope. There were considerable growth disorders at the unions, which included significant overgrowth of stocks and unions and constricted unions. There were cracks in the bark across the union in many graft combinations. Anatomic and histological studies showed accumulation of phenol deposits and necrotic tissues, and there was no continuity of vascular tissues above the union. There were also differences in proliferation of callus tissues among grafted partners. Continuity in wood and bark tissues below the unions supported growth of partially compatible partners, whereas isolated parenchymatous tissues at the union supported growth of incompatible partners. There were many necrotic tissues and unfilled areas above the union. Accumulation of phenolic and necrotic cell deposits, poor or a high level of callusing at the union, and possibly specific incompatibility reactions were implicated as the causes of graft incompatibility in U. kirkiana trees.

Two-dimensional patterns of soluble proteins including three hydrolytic enzymes of mature pollen of tristylous Lythrum salicaria

Lythrum salicaria, now a widespread invasive species, exhibits tristyly, a form of heteromorphic selfincompatibility. In tristyly, each plant exhibits one (and only one) of three morphologically different floral forms. Moreover, each flower produces two types of stamens, and these two exhibit different incompatibility reactions. Differences between stamens of a single flower must be the result of epigenetic phenomena and for that reason, we performed two-dimensional gel electrophoresis (2-DE) to analyze fractions of soluble proteins derived from the pollen coat and protoplast including three hydrolytic enzymes from the six different stamen types (two from each of three floral forms). There were significant differences in the 2-D protein profiles both between pollen from the same flower and between the same type of pollen from two different flowers, in the pollen coat as well as in the protoplast extracts. In five of the six samples of pollen fractions, characteristic peptides were found. Quantitative differences between pollen from the same flower were observed in case of esterases. Furthermore, analysis of proteases and acid phosphatases revealed also qualitative differences between these enzymes in pollen from the same flower.

Food allergies

Food incompatibilities affect approximately 20% of the general population in Western countries. In about one quarter of the affected children and one tenth of affected adults, the incompatibility is based on an allergy, that is, on an immunologically generated incompatibility reaction. Gastrointestinal symptoms occur in a third of these cases. Food allergies are caused by IgE-dependent or IgE-independent immunologic reactions, which lead to an inflammatory reaction, in which mast cells, eosinophilic granulocytes, and other cells are involved. Both genetic and environmental causes are under consideration. New findings concerning the interaction between the innate immune system and intestinal microflora have generated innovative therapeutic concepts, including the use of probiotics to prevent food allergies. The development of recombinant allergens and varieties of allergens will improve diagnostic possibilities and bring new therapeutic options, such as hyposensitization and induction of immunologic tolerance. Food intolerances (nonimmunologic food incompatibilities often caused by specific enzyme deficiencies) must be diagnostically differentiated from food allergies.

Sexual and vegetative compatibility genes in the aspergilli.

Gene flow within populations can occur by sexual and/or parasexual means. Analyses of experimental and in silico work are presented relevant to possible gene flow within the aspergilli. First, the discovery of mating-type (MAT) genes within certain species of Aspergillus is described. The implications for self-fertility, sexuality in supposedly asexual species and possible uses as phylogenetic markers are discussed. Second, the results of data mining for heterokaryon incompatibility (het) and programmed cell death (PCD) related genes in the genomes of two heterokaryon incompatible isolates of the asexual species Aspergillus niger are reported. Het-genes regulate the formation of anastomoses and heterokaryons, may protect resources and prevent the spread of infectious genetic elements. Depending on the het locus involved, hetero-allelism is not tolerated and fusion of genetically different individuals leads to growth inhibition or cell death. The high natural level of heterokaryon incompatibility in A. niger blocks parasexual analysis of the het-genes involved, but in silico experiments in the sequenced genomes allow us to identify putative het-genes. Homologous sequences to known het- and PCD-genes were compared between different sexual and asexual species including different Aspergillus species, Sordariales and the yeast Saccharomyces cerevisiae. Both het- and PCD-genes were well conserved in A. niger. However some point mutations and other small differences between the het-genes in the two A. niger isolates examined may hint to functions in heterokaryon incompatibility reactions.

Association between vegetative compatibility and aflatoxin production by <i>Aspergillus</i> species during intraspecific competition

Intraspecific competition is the basis for biological control of aflatoxins, but there is little understanding of the mechanism(s) by which competing strains inhibit toxin production. Evidence is presented that demonstrates a relationship between strength of the vegetative compatibility reaction and aflatoxin production in Aspergillus flavus and A. parasiticus using the suspended disk culture method. Combining wild-type aflatoxin-producing isolates belonging to different vegetative compatibility groups (VCGs) resulted in a substantial reduction in aflatoxin yield. Pairs of aflatoxin-producing isolates within the same VCG, but showing weak compatibility reactions using complementary nitrate-nonutilizing mutants, also were associated with reduced levels of aflatoxin B1. In contrast, pairings of isolates displaying a strong compatibility reaction typically produced high levels of aflatoxins. These results suggest that interactions between vegetatively compatible wild-type isolates of A. flavus and A. parasiticus are cooperative and result in more aflatoxin B1 than pairings between isolates that are incompatible. Successful hyphal fusions among spore germlings produce a common mycelial network with a larger resource base to support aflatoxin biosynthesis. By comparison, vegetative incompatibility reactions might result in the death of those heterokaryotic cells composed of incompatible nuclei and thereby disrupt the formation of mycelial networks at the expense of aflatoxin biosynthesis.

Development of a molecular genetic linkage map for Colletotrichum lindemuthianum and segregation analysis of two avirulence genes

A framework genetic map was developed for the fungal pathogen Colletotrichum lindemuthianum, the causal agent of anthracnose of common bean (Phaseolus vulgaris L.). This is the first genetic map for any species within the family Melanconiaceae and the genus Colletotrichum and provides the first estimate of genome length for C. lindemuthianum. The map was generated using 106 haploid F1 progeny derived from crossing two Mexican C. lindemuthianum isolates differing in two avirulence genes (AvrclMex and AvrclTO). The map comprises 165 AFLP markers covering 1,897 cM with an average spacing of 11.49 cM. The markers are distributed over 19 major linkage groups containing between 5 and 25 markers each and the genome length was estimated to be approximately 3,241 cM. The avirulence genes AvrclMex and AvrclTO segregate in a 1:1 ratio supporting the gene for gene hypothesis for the incompatible reaction between C. lindemuthianum and P. vulgaris, but could not be incorporated into the genetic map. This initial outline map forms the basis for the development of a more detailed C. lindemuthianum linkage map, which would include other types of molecular markers and allow the location of genes previously isolated and characterized in this species.

Pre-haustorial resistance to broomrape (Orobanche cumana) in sunflower (Helianthus annuus): cytochemical studies

Sunflower broomrape (Orobanche cumana Wallr.) is a root holoparasitic angiosperm considered as one of the major constraints for sunflower production in Mediterranean areas. Breeding for resistance is regarded as the most effective, feasible, and environmentally friendly solution to control this parasite. However, the existing sources of genetic resistance are defeated by the continuous emergence of new more virulent races of the parasite. In this work, the interaction between sunflower and O. cumana has been analysed in order to gain insights into the mechanisms involved in resistance. Two sunflower genotypes were selected showing different behaviour against the new race F of O. cumana, HE-39998 (susceptible) and HE-39999 (resistant), and both compatible and incompatible interactions were compared. Pot and Petri dish bioassays revealed that only HE-39998 plants were severely affected, supporting a high number of successfully established broomrapes to mature flowering, whereas in HE-39999 root tubercles were never observed, resistance being associated with browning symptoms of both parasite and host tissues. Histological aspects of the resistance were further investigated. Suberization and protein cross-linking at the cell wall were seen in the resistant sunflower cells in contact with the parasite, preventing parasite penetration and connection to the host vascular system. In addition, fluorescence and confocal laser microscopy (CLM) observations revealed accumulation of phenolic compounds during the incompatible reaction, which is in agreement with these metabolites playing a defensive role during H. annuus-O. cumana interaction.

Food allergies

Food incompatibilities affect approximately 20% of the general population in Western countries. In about one quarter of the affected children and one tenth of affected adults, the incompatibility is based on an allergy, that is, on an immunologically generated incompatibility reaction. Gastrointestinal symptoms occur in a third of these cases. Food allergies are caused by IgE-dependent orIgE-independent immunologic reactions, which lead to an inflammatory reaction, in which mast cells, eosinophilic granulocytes, and other cells are involved. Both genetic and environmental causes are under consideration. New findings concerning the interaction between the innate immune system and intestinal microflora have generated innovative therapeutic concepts, including the use of probiotics to prevent food allergies. The development of recombinant allergens and varieties of allergens will improve diagnostic possibilities and bring new therapeutic options, such as hyposensitization and induction of immunologic tolerance. Food intolerances (non-immunologic food incompatibilities often caused by specific enzyme deficiencies) must be diagnostically differentiated from food allergies.

The role of complement in biomaterial-induced inflammation

Biomaterials are regularly used in various types of artificial tissues and organs, such as oxygenators, plasmapheresis equipment, hemodialysers, catheters, prostheses, stents, vascular grafts, miniature pumps, sensors and heart aids. Although progress has been made regarding bioincompatibility, many materials and procedures are associated with side effects, in particular bioincompatibility-induced inflammation, infections and subsequent loss of function. After cardiopulmonary bypass, coagulopathies can occur and lead to cognitive disturbances, stroke and extended hospitalization. Hemodialysis is associated with anaphylatoid reactions that cause whole-body inflammation and may contribute to accelerated arteriosclerosis. Stents cause restenosis and, in severe cases, thrombotic reactions. This situation indicates that there is still a need to try to understand the mechanisms involved in these incompatibility reactions in order to be able to improve the biomaterials and to develop treatments that attenuate the reactions and thereby reduce patients’ discomfort, treatment time and cost. This overview deals with the role of complement in the incompatibility reactions that occur when biomaterials come in contact with blood and other body fluids.

Calorimetric studies on the thermal hazard of methyl ethyl ketone peroxide with incompatible substances

In Taiwan, Japan, and China, methyl ethyl ketone peroxide (MEKPO) has caused many severe thermal explosions owing to its thermal instability and reactivity originating from the complexity of its structure. This study focused on the incompatible features of MEKPO as detected by calorimetry. The thermal decomposition and runaway behaviors of MEKPO with about 10 wt.% incompatibilities, such as H 2SO 4, HCl, NaOH, KOH, FeCl 3, and FeSO 4, were analyzed by dynamic calorimeter, differential scanning calorimetry (DSC) and adiabatic calorimeter, vent sizing package 2 (VSP2). Thermokinetic data, such as onset temperature, heat of decomposition, adiabatic temperature rise, and self-heat rate, were obtained and assessed. Experimental data were used for determining the incompatibility rating on hazards. From the thermal curves of MEKPO with assumed incompatible substances detected by DSC, all the onset temperatures in the other tests occurring earlier advanced, especially with alkaline or ferric materials. In some tests, significant incompatible reactions were found. Adiabatic runaway behaviors for simulating the worst case scenario were performed by using VSP2. These calorimetric data led to the same results that the alkaline or ferric solution was the most incompatible with MEKPO.

Auxotrophic mutant of the cyanobacterium Nostoc muscorum showing absolute requirement of Cs+ or Rb+ for diazotrophy and autotrophy

Caesium-resistant (Cs(+)-R) mutant clones of the cyanobacterium Nostoc muscorum were characterized for diazotrophic growth in a medium devoid of Cs(+) or Rb(+) or both. Cs(+)-R phenotype suffered severe genetic damage of a pleiotropic nature affecting diazotrophic growth, chlorophyll a content, nitrogenase activity and photosynthetic O(2) evolution. Mutation leading to development of Cs(+)-R phenotype could be overcome by availability of Cs(+)/Rb(+). Parent and mutant strains were similar with respect to their Cs(+)/Rb(+) uptake. Available data suggests operation of an efficient coupling of the two incompatible reactions viz. oxygenic photosynthesis and oxygen sensitive N(2) fixation in this cyanobacterium.