Types Of Incompatibility Research Articles

Genomic mechanisms and consequences of diverse postzygotic barriers between monkeyflower species.

The evolution of genomic incompatibilities causing postzygotic barriers to hybridization is a key step in species divergence. Incompatibilities take two general forms - structural divergence between chromosomes leading to severe hybrid sterility in F1 hybrids and epistatic interactions between genes causing reduced fitness of hybrid gametes or zygotes (Dobzhansky-Muller incompatibilities). Despite substantial recent progress in understanding the molecular mechanisms and evolutionary origins of both types of incompatibility, how each behaves across multiple generations of hybridization remains relatively unexplored. Here, we use genetic mapping in F2 and RIL hybrid populations between the phenotypically divergent but naturally hybridizing monkeyflowers Mimulus cardinalis and M. parishii to characterize the genetic basis of hybrid incompatibility and examine its changing effects over multiple generations of experimental hybridization. In F2s, we found severe hybrid pollen inviability (< 50% reduction vs. parental genotypes) and pseudolinkage caused by a reciprocal translocation between Chromosomes 6 and 7 in the parental species. RILs retained excess heterozygosity around the translocation breakpoints, which caused substantial pollen inviability when interstitial crossovers had not created compatible heterokaryotypic configurations. Strong transmission ratio distortion and inter-chromosomal linkage disequilibrium in both F2s and RILs identified a novel two-locus genic incompatibility causing sex-independent gametophytic (haploid) lethality. The latter interaction eliminated three of the expected nine F2 genotypic classes via F1 gamete loss without detectable effects on the pollen number or viability of F2 double heterozygotes. Along with the mapping of numerous milder incompatibilities, these key findings illuminate the complex genetics of plant hybrid breakdown and are an important step toward understanding the genomic consequences of natural hybridization in this model system.

Simulating Multivariate Multidimensional Homogenous Non-Gaussian Field Based on Unified Hermite Polynomial Model

Reasonable simulation of stochastic fields is a key prerequisite for addressing stochastic mechanics problems with Monte Carlo simulation solver. This paper presents a novel method to simulate m-variate and n-dimensional (mV-nD) homogenous non-Gaussian fields according to the prescribed power spectral density matrix (PSDM) and first four moments. In the proposed method, the unified Hermite polynomial model (UHPM) is first extended to mV-nD homogenous non-Gaussian fields. Then, based on the extended UHPM, a complete transformation model from the normalized non-Gaussian correlation function matrix (CFM) into the underlying Gaussian CFM with its applicable range is derived. In addition, two types of potential incompatibility of the transformation arising from the prescribed PSDM and first four moments are defined and neatly solved. Finally, a unified simulation framework for mV-nD homogenous non-Gaussian fields is presented, where the fast Fourier transform technique can be embedded in both spectral representation method and Wiener-Khintchine transformation to speed up the simulation progress. Two numerical examples including the simulations of non-Gaussian wind fields and non-Gaussian fields of material properties are presented to demonstrate the effectiveness of the proposed method.

Phase transformation and incompatibility at grain boundaries in zirconia-based shape memory ceramics: a micromechanics-based simulation study

Zirconia-based shape memory ceramics (SMCs) exhibit anisotropic mechanical response when undergoing elastic deformations as well as during austenite–martensite phase transformation. This behavior results in different types of strain incompatibility at grain boundaries, which we study here using a micromechanical model. A single-crystal model is implemented to provide a full mechanistic three-dimensional description of the anisotropic elastic as well as martensitic transformation stress–strain response, including non-Schmid behavior caused by the significant volume change during martensitic transformation. This model was calibrated to and validated against compression tests of single-crystal zirconia micro-pillars conducted previously, and then used to model bi-crystals. Upon the introduction of a grain boundary, the simulation provides detailed information on the nucleation and evolution of martensite variants and stress distribution at grain boundaries. We identify bi-crystal configurations which result in very large stress concentrations at very low deformations due to elastic incompatibility, as well as others where the elastic incompatibility is relatively low and stress concentrations only occur at large transformation strains. We also show how this approach can be used to explore the misorientation space for quantifying the level of elastic and transformation incompatibility at SMCs grain boundaries.Graphical abstractMicromechanics models provide insights on grain boundary elastic and phase transformation strain incompatibility in shape memory zirconia

Simulating multivariate stationary non-Gaussian process based on wavenumber–frequency spectrum and unified Hermite polynomial model

It is of importance to model the input excitations considering the spatial variation and non-Gaussianity for the reliability evaluation of long span structures. The existing multivariate stationary non-Gaussian simulation methods are mainly based on the target marginal distribution and cross-spectrum matrix. Due to the Cholesky decomposition of cross-spectrum matrix, the computational cost of these methods increases rapidly with the increase of spatial points. Therefore, this paper develops a novel simulation method based on the wavenumber–frequency spectrum and unified Hermite polynomial model (UHPM). Firstly, UHPM is extended to the homogenous and stationary non-Gaussian field. Then, a complete transformation model from homogenous and stationary non-Gaussian auto-correlation function (ACF) into underlying Gaussian ACF with its applicable range is proposed. Furthermore, two types of incompatibility between the first four marginal moments and wavenumber–frequency spectrum are discussed, and the corresponding remedies are provided. To facilitate the calculation, the 2D-Fast Fourier Transform (FFT) technique is embedded in the Wiener–Khintchine transformation and spectral representation method (SRM). Finally, a unified simulation framework for multivariate stationary non-Gaussian process based on its relationship to the homogenous and stationary non-Gaussian field is presented. Two numerical examples, involving the simulations of non-Gaussian wind velocities and ground motion accelerations, are investigated to verify the capabilities of the proposed method.

Role of Viruddha Ahara towards Skin and Allergic Disorders; an Ayurveda Review

Viruddha Ahara is Ayurveda view of food incompatibility; Viruddha Ahara referred several types of food incompatibility including food–food interactions and food processing interactions, etc. Diet and its combinations that affects metabolism of tissue, inhibits process of tissue formation, alter physiological process of body and having opposite property, etc. are termed as Viruddha Ahara or incompatible food. The inappropriate quantity and quality of food and improper timing of meal, etc. also comes under the heading of Viruddha Ahara. With respect to concept of Viruddha Ahara Ayurveda has described different food incompatibilities i.e.; Samskar Viruddha, Samyoga Viruddha and Veerya Viruddha, etc. Viruddha ahara can triggers pathogenesis of several diseases including Visarpa, intoxication, Shukra Dhatu Dushti, rhinitis, infertility, Kustha roga and allergic disorders, etc. Present article explored role of Viruddha ahara in skin and allergic disorders.

Phase Transformation and Incompatibility at Grain Boundaries in Zirconia-Based Shape Memory Ceramics: A Micromechanics-Based Simulation Study

Zirconia-based shape memory ceramics (SMCs) exhibit anisotropic mechanical response when undergoing elastic deformations as well as during austenite-martensite phase transformation. This behavior results in different types of strain incompatibility at grain boundaries, which we study here using a micromechanical model. A single-crystal model is developed to provide a full mechanistic three-dimensional description of the anisotropic elastic as well as martensitic transformation stress-strain response, including non-Schmid behavior caused by the significant volume change during martensitic transformation. This model was calibrated to and validated against compression tests of single-crystal zirconia micro-pillars, prior to being used to model bi-crystals. Upon the introduction of a grain boundary, the simulation provides detailed information on the nucleation and evolution of martensite variants and stress distribution at grain boundaries. We identify bicrystal configurations which result in very large stress concentrations at very low deformations due to elastic incompatibility, as well as others where the elastic incompatibility is relatively low and stress concentrations only occur at large transformation strains. We also show how this approach can be used to explore the misorientation space for quantifying the level of elastic and transformation incompatibility at SMCs grain boundaries.

Plastic accommodation during tensile deformation of gradient structure

Gradient structure (GS) possesses a typical trans-scale grain hierarchy with varying internal plastic stability, and the mutual plastic accommodation plays a crucial role in its superior strength-ductility combination. Using the in-situ synchrotron X-ray diffraction (XRD) during tensile loading, we measured lattice strains sequentially from the nanostructured (NS) surface layer to the central coarsegrained (CG) layer to elucidate when and how plastic accommodation occurs and evolves within the GS, along with their roles in plastic deformation and strain hardening. Throughout the tensile deformation, two types of plastic incompatibility occur in the GS. One is an extended elastoplastic transition due to layer-by-layer yielding. The other is strain localization and softening in the NS layer, in contrast with the stable plastic deformation in the CG layer. Plastic accommodation thus occurs concurrently and manifests as both an inter-layer and intra-layer change of stress state throughout tensile deformation. This produces different micromechanical responses between layers. Specifically, the NS layer initially experiences strain hardening followed by an elastoplastic deformation. The hetero-deformation induced hardening, along with forest hardening, facilitates a sustainable tensile strain in the NS layer, comparable to that in the CG layer.

Incommensurability, types of phenomena and relevant incompatibility (part III)

Incommensurability, types of phenomena and relevant incompatibility (part III)

Incommensurability, types of phenomena and relevant incompatibility (part II)

Although incommensurability between theories has been object of study during many years, there does not seem to be a clear consensus regarding the notion of meaning according to which it should be characterised. Based on the notion of incommensurability proposed here, the common ground between incommensurable theories is neither determined by the sense nor by the reference of the relevant terms, but by a given phenomenon type, which fixes the subject matter of inquiry. Phenomenon types are understood as expressions that are associated with some phenomenon and describable or understandable in some language. In this proposal, two theories can refer to a same phenomenon type even if they are mutually incommensurable about the concepts used in them to grasp it. This possibility may serve as a way of fixing the subject matter of an investigation and, thus, to characterise the common ground between incommensurable paths of inquiry, offering also a strategy to solve some remaining problems associated with realism and scientific progress.

Incommensurability, types of phenomena and relevant incompatibility (part I)

Although incommensurability between theories has been object of study during many years, there does not seem to be a clear consensus regarding the notion of meaning according to which it should be characterised. Based on the notion of incommensurability proposed here, the common ground between incommensurable theories is neither determined by the sense nor by the reference of the relevant terms, but by a given phenomenon type, which fixes the subject matter of inquiry. Phenomenon types are understood as expressions that are associated with some phenomenon and describable or understandable in some language. In this proposal, two theories can refer to a same phenomenon type even if they are mutually incommensurable about the concepts used in them to grasp it. This possibility may serve as a way of fixing the subject matter of an investigation and, thus, to characterise the common ground between incommensurable paths of inquiry, offering also a strategy to solve some remaining problems associated with realism and scientific progress.

Interspecific incompatibility in the wide hybridization of plants and ways to overcome it

Wide hybridization is an important factor of angiosperm speciation and provides an introgression of genes between species. In experimental conditions, wide hybridization is used to increase the genetic diversity of cultivated plants. Since the emergence of reproductive barriers is of great importance for speciation, plants’ capacity for wide crosses is determined by the possibility of overcoming these barriers. This review discusses the main types of incompatibility in wide crossing plants, as well as the factors and methodological approaches that contribute to overcoming them. The role of Kr genes, which determine incompatibility between wheat and rye, is one of the examples of a prezygotic isolation mechanism. Postzygotic incompatibility may be associated with a highly pronounced genetic and epigenetic variability induced by wide crossings. The early stages of the postzygotic period are crucial for developing hybrid seeds due to an embryo’s death, including those associated with uniparental chromosome elimination in hybrid cells and abnormal development of the endosperm. The depression and lethality of F1 hybrids may be the result of interaction between complementary genes, which cause hybrid necrosis, hybrid chlorosis, and hybrid dwarfness. The causes of hybrid sterility are discussed. Nuclear-cytoplasmic interactions are regarded as one of the mechanisms of incompatibility in wide crosses. Reciprocal hybrids and alloplasmic lines are the main models for studying cytoplasm effects and nuclear-cytoplasmic interactions. Problems concerning work with their models are emphasized. There are some examples underlying the fact that alloplasmic lines are not a plain combination of the nuclear genome and cytoplasm of different species. The development of alloplasmic lines is connected with the structural and functional variability of nuclear and organelle genomes.

Biparental chloroplast inheritance leads to rescue from cytonuclear incompatibility.

Although organelle inheritance is predominantly maternal across animals and plants, biparental chloroplast inheritance has arisen multiple times in the angiosperms. Biparental inheritance has the potential to impact the evolutionary dynamics of cytonuclear incompatibility, interactions between nuclear and organelle genomes that are proposed to be among the earliest types of genetic incompatibility to arise in speciation. We examine the interplay between biparental inheritance and cytonuclear incompatibility in Campanulastrum americanum, a plant species exhibiting both traits. We first determine patterns of chloroplast inheritance in genetically similar and divergent crosses, and then associate inheritance with hybrid survival across multiple generations. There is substantial biparental inheritance in C.americanum. The frequency of biparental inheritance is greater in divergent crosses and in the presence of cytonuclear incompatibility. Biparental inheritance helps to mitigate cytonuclear incompatibility, leading to increased fitness of F1 hybrids and recovery in the F2 generation. This study demonstrates the potential for biparental chloroplast inheritance to rescue cytonuclear compatibility, reducing cytonuclear incompatibility's contribution to reproductive isolation and potentially slowing speciation. The efficacy of rescue depended upon the strength of incompatibility, with a greater persistence of weak incompatibilities in later generations. These findings suggest that incompatible plastids may lead to selection for biparental inheritance.

Interspecific incompatibility in wide hybridization of plants and ways to overcome

Wide hybridization is an important factor of angiosperm speciation and provides an introgression of genes between species. In experimental conditions wide hybridization is used to increase the genetic diversity of cultivated plants. Since the emergence of reproductive barriers is of great importance for speciation, plant capacity for wide crosses is determined by a possibility of overcoming these barriers. The review discusses the main types of incompatibility in wide crossing plants, as well as factors and methodological approaches that contribute to overcoming them. The role of Kr genes, which determine incompatibility between wheat and rye, is one of the examples of prezygotic isolation mechanism. Postzygotic incompatibility may be associated with a highly pronounced genetic and epigenetic variability induced by wide crossings. Early stages of the postzygotic period are crucial for developing hybrid seeds due to embryo’s death, including those associated with uniparental chromosome elimination in hybrid cells and abnormal development of the endosperm. A depression and a lethality of F1 hybrids may be the result of interaction between complementary genes, which cause hybrid necrosis, hybrid chlorosis, and hybrid dwarfness. The causes of hybrid sterility are discussed. Nuclearcytoplasmic interactions are regarded as one of the mechanisms of incompatibility in wide crosses. Reciprocal hybrids and alloplasmic lines are the main models for studying cytoplasm effects and nuclearcytoplasmic interactions. Problems concerning work with their models are emphasized. There are some examples underlining the fact that alloplasmic lines are not a plain combination of nuclear genome and cytoplasm of different species. Development of alloplasmatic lines is connected with structural and functional variability of nuclear and organelle genomes.

RAPID EVOLUTION OF ASYMMETRIC REPRODUCTIVE INCOMPATIBILITIES IN STALK‐EYED FLIES

The steps by which isolated populations acquire reproductive incompatibilities remain poorly understood. One potentially important process is postcopulatory sexual selection because it can generate divergence between populations in traits that influence fertilization success after copulation. Here we present a comprehensive analysis of this form of reproductive isolation by conducting reciprocal crosses between variably diverged populations of stalk-eyed flies (Teleopsis dalmanni). First, we measure seven types of reproductive incompatibility between copulation and fertilization. We then compare fertilization success to hatching success to quantify hybrid inviability. Finally, we determine if sperm competition acts to reinforce or counteract any incompatibilities. We find evidence for multiple incompatibilities in most crosses, including failure to store sperm after mating, failure of sperm to reach the site of fertilization, failure of sperm to fertilize eggs, and failure of embryos to develop. Local sperm have precedence over foreign sperm, but this effect is due mainly to differences in sperm transfer and reduced hatching success. Crosses between recently diverged populations are asymmetrical with regard to the degree and type of incompatibility. Because sexual conflict in these flies is low, postcopulatory sexual selection, rather than antagonistic coevolution, likely causes incompatibilities due to mismatches between male and female reproductive traits.

How do I approach ABO‐incompatible hematopoietic progenitor cell transplantation? (CME)

H uman leukocyte antigen (HLA) matching is critically important for successful hematopoietic progenitor cell (HPC) transplantation because the rates of engraftment and transplant outcomes are strongly influenced by the degree of match. This is largely because HLA antigens are expressed on immature pluripotent stem cells. In contrast, ABO incompatibility is not a barrier to successful HPC transplantation because ABO blood group antigens are not expressed on pluripotent or early committed HPCs. HLA and ABO antigens are encoded by different genes; thus it is common that potential donors who are fully HLA matched have an ABO incompatibility. Approximately 40 to 50% of HPC transplants are ABO incompatible and are now performed using bone marrow (HPC-M), apheresis-derived peripheral blood progenitor cells (HPCA), and umbilical cord blood (HPC-C) as HPC sources. Three types of ABO incompatibility exist: major, minor, and bidirectional. A total of 20 to 25% of HPC transplants have a major ABO incompatibility, 20 to 25% a minor ABO incompatibility, and up to 5% a bidirectional incompatibility. Each presents a unique set of potential adverse consequences, including early acute hemolysis that can be ameliorated through HPC product processing to remove incompatible red blood cells (RBCs) or plasma (Table 1). In these cases, the recipient must be closely monitored both at the time of the infusion and in the posttransplant period because serious events can occur many days later. Accreditation agencies such as AABB and the Foundation for the Accreditation of Cellular Therapy (FACT) require that all donors be tested for ABO group and D type before the collection of HPC-A or HPC-M and that HPC-C be typed after product processing before cryopreservation. The testing and its required documentation in the medical record need to be done in accordance with institutional standard operating procedures. Current FACT standards also require that “for allogeneic cellular therapy products containing RBCs at the time of administration, a test for ABO group and Rh type shall be performed on the first product collected, or on blood obtained from the donor at the time of the first collection.” At our institution, the donor ABO group and D type is tested as part the donor evaluation process. Additional donor ABO group and D testing is performed on each collection day from blood samples obtained at time of collection. If donor blood sample is not available for a particular collection, confirmatory typing is performed on a product sample on the day of product processing. For all fresh HPC products received from outside facilities, confirmatory ABO group and D testing is performed before further product processing. HPC-C units are received in the frozen state and are not subject to repeat testing.

ARE SPECIES REAL? THE SHAPE OF THE SPECIES BOUNDARY WITH EXPONENTIAL FAILURE, REINFORCEMENT, AND THE “MISSING SNOWBALL”

Under simple assumptions, the evolution of epistatic "Dobzhansky-Muller" incompatibilities between a pair of species should yield an accelerating decline of log overall reproductive compatibility--a "snowball" effect that might rapidly provide new species with "reality." Possible alternatives include: (1) simple exponential failure, giving a linear rate of log compatibility loss, and (2) "slowdown," likely during reinforcement in which mate choice evolves to prevent deleterious hybridization, yielding a decelerating log compatibility loss. In analyses of multiple datasets, we find little support for the snowball effect, except possibly in Lepidoptera hybrid viability. The snowball predicts a slow initial rate of incompatibility acquisition, with low initial variance; instead, highly variable compatibility is almost universally observed at low genetic distances. Another deviation from predictions is that reproductive isolation usually remains incomplete until long after speciation. These results do not disprove snowball compatibility decay, but can result if large deleterious effects are due to relatively few genetic changes, or if different types of incompatibility evolve at very different rates. On the other hand, data on Bacillus and Saccharomyces, as well as theories of chromosomal evolution, suggest that some kinds of incompatibility accumulate approximately linearly, without Dobzhansky-Muller effects. In microorganisms, linearity can result from direct negative effects of DNA sequence divergence on compatibility. Finally, a decelerating slowdown model is supported for sympatric Leptasterias starfish, and in Drosophila prezygotic isolation in sympatry but not allopatry, providing novel comparative evidence for reinforcement.

High-Resolution Genome-Wide Dissection of the Two Rules of Speciation in Drosophila

Postzygotic reproductive isolation is characterized by two striking empirical patterns. The first is Haldane's rule—the preferential inviability or sterility of species hybrids of the heterogametic (XY) sex. The second is the so-called large X effect—substitution of one species's X chromosome for another's has a disproportionately large effect on hybrid fitness compared to similar substitution of an autosome. Although the first rule has been well-established, the second rule remains controversial. Here, we dissect the genetic causes of these two rules using a genome-wide introgression analysis of Drosophila mauritiana chromosome segments in an otherwise D. sechellia genetic background. We find that recessive hybrid incompatibilities outnumber dominant ones and that hybrid male steriles outnumber all other types of incompatibility, consistent with the dominance and faster-male theories of Haldane's rule, respectively. We also find that, although X-linked and autosomal introgressions are of similar size, most X-linked introgressions cause hybrid male sterility (60%) whereas few autosomal introgressions do (18%). Our results thus confirm the large X effect and identify its proximate cause: incompatibilities causing hybrid male sterility have a higher density on the X chromosome than on the autosomes. We evaluate several hypotheses for the evolutionary cause of this excess of X-linked hybrid male sterility.

Orality and Literacy

• Summary: This article examines the issue of orality and literacy and reflects critically on their relevance, challenges and opportunities in relation to social work practice and education. • Findings: The findings from language studies on the effects of literacy on individuals are examined, identifying the significant features of the oral and literate mind-sets. Using these findings, the hiatus between the literate mode of education and oral mode of practice in social work, and its possible effects, are scrutinized. Three types of incompatibility are identified: between clients and social workers; between direct and indirect practice; and between education and practice. • Applications : Empirical studies can be conducted in education and practice based on the deliberations of this article to test the validity of the assertions and the heuristic tools suggested. Social work educators and practitioners may want to redress the balance between the oral and written modes of communication in curriculum design, methods of assessment and accounting for practice, with due recognition of the orally mediated mode of knowledge construction and dissemination.

Making the Quantum of Relevance

The two Heisenberg Uncertainties (UR) entail an incompatibility between the two pairs of conjugated variables E, t and p, q. But incompatibility comes in two kinds, exclusive of one another. There is incompatibility defineable as: (p → − q) & (q→ − p) or defineable as [(p →− q) & (q →− p)] ↔ r. The former kind is unconditional, the latter conditional. The former, in accordance, is fact independent, and thus a matter of logic, the latter fact dependent, and thus a matter of fact. The two types are therefore diametrically opposed. In spite of this, however, the existing derivations of the Uncertainties are shown here to entail both types of incompatibility simultaneously. Δ E Δ t ≥ h is known to derive from the quantum relation E = hν plus the Fourier relation Δ ν Δ t ≥ 1. And the Fourier relation assigns a logical incompatibility between Δ ν = 0, Δ t = 0. (Defining a repetitive phenomenon at an instant t → 0 is a self contradictory notion.) An incompatibility, therefore, which is fact independent and unconditional. How can one reconcile this with the fact that Δ EΔ t exists if and only if h > 0, which latter supposition is a factual truth, entailing that a Δ E = 0, Δ t = 0 incompatibility should itself be fact dependent? Are we to say that E and t are unconditionally incompatible (via Δ ν Δ t ≥ 1) on condition that E = hν is at all true? Hence, as presently standing, the UR express a self-contradicting type of incompatibility. To circumvent this undesirable result, I reinterpret E = hν as relating the energy with a period. Though only one such period. And not with frequency literally. (It is false that E = ν . It is true that E = ν times the quantum.) In this way, the literal concept of frequency does not enter as before, rendering Δ ν Δ t ≥ 1 inapplicable. So the above noted contradiction disappears. Nevertheless, the Uncertainties are derived. If energy is only to be defined over a period, momentum only over a distance (formerly a wavelength) resulting during such period, thus yielding quantized action of dimensions Et = pq, then energies will become indefinite at instants, momenta indefinite at points, leading, as demanded, to (symmetric!) Δ E Δ t = Δ p Δ q ≥ h’s.

Stylar glycoproteins bind to S‐RNase in vitro

S-RNases determine the specificity of S-specific pollen rejection in self-incompatible plants of the Solanaceae, Rosaceae, and Scrophulariaceae. They are also implicated in at least two distinct types of unilateral interspecific incompatibility in Nicotiana. However, S-RNase itself is not sufficient for most types of pollen rejection, and evidence for its direct interaction with pollen tubes is limited. Thus, non-S-RNase factors also are required for pollen rejection. As one approach to identifying such factors, we tested whether SC10-RNase from Nicotiana alata would bind to other stylar proteins in vitro. SC10-RNase was immobilized on Affi-gel, and binding proteins were analyzed by SDS-PAGE and immunoblotting. In addition to SC10-RNase and a small protein similar to lily chemocyanin, the most prominent binding proteins include NaTTS, 120K, and NaPELPIII, these latter three being arabinogalactan proteins previously shown to interact directly with pollen tubes. We also show that SC10-RNase and these glycoproteins migrate as a complex in a native PAGE system. Our hypothesis is that S-RNase forms a complex with these glycoproteins in the stylar ECM, that the glycoproteins interact directly with the pollen tubes and thus that the initial interaction between the pollen tube and S-RNase is indirect.