Self-compatible Research Articles

S-related protein can be recombined with self-compatibility in interspecific derivatives ofLycopersicon

Stylar proteins involved in the self-incompatible (SI) response of Lycopersicon hirsutum have been identified and mapped to the locus that controls SI (S locus). L. esculentum, a self-compatible (SC) species of cultivated tomato, does not display these proteins. Hybrids between SC L. esculentum and SI L. hirsutum are self-sterile despite these individuals bearing pollen containing the S allele of L. esculentum. In progeny derived from backcrossing the hybrids to L. esculentum, there was a strong correlation between the presence of the S allele from L. hirsutum and self-infertility. However, this relationship was uncoupled in a number of backcross (BC) progeny. The SI response appeared to be nonexistent in two self-fertile BC individuals that were heterozygous for the S allele of L. hirsutum, based on Mendelian segregation of a tightly linked DNA marker, CD15, in selfed progeny. Among these progeny self-fertile individuals that were homozygous for the L. hirsutum allele of the linked marker were also determined to be homozygous for an S-related proteins are not sufficient to elicit a self-incompatible response in L. esculentum and that there is a mutation(s) in L. esculentum somewhere other than the S locus that leads to self-compatibility.

Incompatibility in Flowering Plants: Adaptation of an Ancient Response.

Angiosperms differ in their ability to fertilize themselves. Differ? ences in self-compatibility (SC) presumably reflect ancient events because both self-compatible and self-incompatible plants occur throughout the angiosperms. It has often been assumed that the first angiosperms were self-compatible and that self-incompatibility (Sl) is a derived condition, but this has not been proven definitively. Another possibility is that Sl is the ancient state and SC the derived condition. That this may be the case grows out of a consideration of the requirements for the development of angiospermy itself. Although the principal characteristic of the angiosperms is usu? ally regarded as a closed carpel, the existence of a small number of species in which the carpel is open (e.g., the monocotyledon genus Butomus and the dicotyledon genus Reseda) shows that closure of the carpel is not essential for angiospermous reproduction. What does appear to define the angiosperms is the ability of the male gametophyte, repre? sented by the pollen tube, to grow through intact sporophytic tissue (commonly the style and nucellus), a process termed penetrative siphonogamy. The angiosperms are the only group of land plants in which the pollen tube carrying the male ga? metes is known to maintain intimate cell-cell contact with the

Pollen Tube Behavior Related to Self-incompatibility in Interspecific Crosses of Fagopyrum.

The pollen tube growth in interspecific pollination was investigated to assess interspecific cross-incompatibility among ten species at the prezygotic stage and also to analyze the evolutional relationship between self-incompatible (SI) and self-compatible (SC) species. Total 136 pollination treatments were conducted under pollinator-free conditions at the full flowering stage. Florets were harvested 4 or 24 hours after pollination, and pollen tube length was measured under a fluorescent microscope. Measurements were made on the longest pollen tube for each style, and 6-36 styles were observed per pollination treatment. The following conclusions were derived from this study. 1) Unilateral incompatibility was observed among the SI and SC species. ing, it is important to analyze the relationship between 2) Dimorphic self-incompatibility system influenced the re-cross-incompatibility and self-incompatibility

Dry stigmas, water and self-incompatibility in Brassica

The evolution of dry stigmas has been accompanied by the development — in the pollen — of mechanisms for accessing water from the stigmatic epidermis. Development of self- and cross-pollen on the stigmatic surface has been examined in Brassica oleracea, focusing on the hydration of the grains. Unlike self-compatible (SC) Arabidopsis thaliana, pollen hydration of self-incompatible (SI) Brassica oleracea is preceded by a latent period of between 30–90 min, which is significantly shortened by inhibition of protein synthesis in the stigma. Physiological experiments, some with isolated pollen coatings, indicate that during the latent period signals passing from the pollen to the sigma are responsible for readying the stigmatic surface for penetration and — after self-pollination — activation of the SI system. The changes at the stigma surface include the expansion of the outer layer of the cell wall beneath the grain. This expansion does not occur following self-pollination, when coating-derived signals stimulate a stigmatic response which interrupts hydration and arrests grain development. Cell manipulation studies suggest that self grains are not inhibited metabolically, but are physiologically isolated from the subjacent stigmatic papilla. This focusing of the SI response at the pollen-stigma interface ensures that a single papilla can simultaneously accept cross-pollen and reject self-grains. The evolution of this highly efficient SI system is disussed in the perspective of pathogen-defence mechanisms known also to be located in epidermal cells.

Stylar water potential and unilateral interspecific incompatibility inSolanaceae

Water and osmotic potentials were measured in young and mature styles of selfcompatible (SC) and selfincompatible (SI) species ofSolanaceae. For mature flowers, the stylar water and osmotic potentials were considerably lower in SI speciesNicotiana alata andPetunia hybrida than in SC speciesN. sylvestris andN. tabacum. Stylar water content (in % fresh mass) was also significantly lower in SI species (N. alata, P. hybrida, diploid clones of potato) than in SC species (N. acuminata, N. glauca, N. paniculata, N. sylvestris, N. tabacum). For flower buds younger than 2 d before anthesis, no differences in stylar water potential betweenN. alata (SI) andN. tabacum (SC) were observed. During further flower bud development the stylar water potential inN. alata decreased more expressively than inN. tabacum. Pollen culture in media with various concentrations of sucrose or polyethylene glycol revealed that optimal water potential for pollen tube growth was lower inN. alata than inN. tabacum. The differences were similar as for differences in stylar water potential. The results are considered in relation to possible involvement of stylar water potential in unilateral interspecific incompatibility inSolanaceae.

Protein expression of a self-compatible allele from Lycopersicon peruvianum: introgression and behavior in a self-incompatible background

Lycopersicon peruvianum (wild tomato) is a gametophytic self-incompatible (SI) species. One natural population has been shown to harbor a self-compatible (SC) allele. A stylar protein associated with the self-compatibility allele has been elucidated using SDS-PAGE. The temporal and spatial expression of this protein is presented and compared with protein expression of two SI alleles. Hybrids containing the SC and SI alleles were used in a backcrossing program to introgress the SC allele into SI backgrounds in six independent lines. Controlled pollinations and SDS-PAGE were used to identify and select classes of progeny. After four backcross generations (approximately 97% recovery of the SI backgrounds) the SC allele still confers self-fertility in lines that contain this allele, providing evidence that the mutation to SC occurred at the S-locus and that the associated protein is likely responsible.

Self-incompatibility is codominant in intraspecific hybrids of self-compatible and self-incompatible Lycopersicon peruvianum and L. hirsutum based on protein and DNA marker analysis

Self-compatibility was investigated separately in two species of tomato, Lycopersicon peruvianum and L. hirsutum. The codominant expression of self-compatibility (SC)/self incompatibility (SI) was established using intraspecific hybrids of SC and SI hybrids. In SC L. peruvianum, a major stylar protein of approximately 29 kDa cosegregates with self-compatibility in the progeny of SC/SI hybrids. The SC/SI hybrids are self-fertile, but only partially so, since the SI allele present in the hybrids is capable of eliminating certain genotypes in the resultant progeny. In L. hirsutum, the majority of hybrids between one accession of SI L. hirsutum f. hirsutum and one of SC L. hirsutum f. glabratum are self-fertile. Analysis of the progeny revealed that the SC and SI alleles are codominant in this species as well. A protein product for the SC allele is not obvious in style extracts of L. hirsutum f. glabratum. Segregating progeny from SC/SI hybrids of L. hirsutum were used to map the S locus against five RFLP markers on chromosome 1, and estimated map distances are given. In addition, evidence is presented that indicates that one of the DNA markers, CD15, is duplicated in L. hirsutum f. glabratum, and the duplication is not linked to the S locus.

Phosphorylation of pollen proteins in relation to self-incompatibility in rye (Secale cereale L.)

The gametophytic two-locus self-incompatibility (SI) system in rye was investigated in view of a possible involvement of protein phosphorylation and Ca2+ as constituents of a signal transduction mechanism. Phosphorylation kinetics in pollen grains was found to be significantly different after in vitro treatment of pollen with either “cross” or “self” stigma proteins, with a pronounced phosphorylation activity in self-treated pollen grains. Loss of SI in self-compatible (SC) mutants was associated with a significantly decreased basic phosphorylation activity in untreated pollen grains as compared to SI genotypes. Separation of phosphorylated pollen proteins by SDS-PAGE reveals four major proteins in the MW range of 43–82 kDa which were differently phosphorylated in SI vs SC genotypes as well as in cross vs self-treated pollen grains. Application of different protein kinase inhibitors and the Ca2+ antagonists verapamil and La3+ to isolated stigmas resulted in an inhibition of the SI response in in vitro self-pollination. The role of protein kinases and Ca2+ as constituents of a putative SI-specific signal transduction mechanism is discussed.

Field performance of self-compatible and an equal proportion mixture of self-compatible and self-incompatible summer rape lines at two Alberta locations in 1989

Two sporophytic self-incompatibility (SI) alleles were introgressed from Brassica napus rapid cycling material into five self-compatible (SC) lines of oilseed summer rape. The field performance of segregating BC2F2 lines (SC:SI 1:1) was compared with the corresponding SC lines using a split-plot field design. Plants of the SC-SI mixed stands produced, in comparison to plants of the SC plots, more siliques on the main raceme, but the siliques contained fewer seed suggesting that SI plants might not have been fully fertilised. Key words: Rape (summer), sporophytic self-incompatibility

Potential for the Loss of Self-Incompatibility in Pollen-Limited Populations of Mayapple (Podophyllum peltatum)

Self-compatibility (SC) appears to be a derived trait in many unrelated taxa. A major selective force that could lead to the evolution of SC from self-incompatibility (SI) is inadequate pollination. Here we show that seed set is strongly pollenlimited in populations of mayapple, Podophyllum peltatum (Berberidaceae). Hand-pollination led to a 26-fold increase in seed set as compared to natural levels in 1989, and to a fivefold increase in 1990. The species is SI, but in a survey of 49 colonies in Ohio we found three that had more than 50% fruit set from self pollen (as compared to about 90% fruit set from hand-outcrossed flowers). However, when hand-selfing yielded fruits, the number of seeds per fruit was only about 10% of the seed set from hand-outcrossing. We discuss the relative fecundity of putative SC and SI genotypes in terms of conditions needed for the spread of SC in mayapple populations (little or no morphological change would be needed to ensure within-flower selfing). Seed set from putative SC genotypes appeared to be low enough to prevent them from replacing SI genotypes, even in the face of infrequent pollinator visits.

POTENTIAL FOR THE LOSS OF SELF‐INCOMPATIBILITY IN POLLEN‐LIMITED POPULATIONS OF MAYAPPLE (PODOPHYLLUM PELTATUM)

Self‐compatibility (SC) appears to be a derived trait in many unrelated taxa. A major selective force that could lead to the evolution of SC from self‐incompatibility (SI) is inadequate pollination. Here we show that seed set is strongly pollenlimited in populations of mayapple, Podophyllum peltatum (Berberidaceae). Hand‐pollination led to a 26‐fold increase in seed set as compared to natural levels in 1989, and to a fivefold increase in 1990. The species is SI, but in a survey of 49 colonies in Ohio we found three that had more than 50% fruit set from self pollen (as compared to about 90% fruit set from hand‐outcrossed flowers). However, when hand‐selfing yielded fruits, the number of seeds per fruit was only about 10% of the seed set from hand‐outcrossing. We discuss the relative fecundity of putative SC and SI genotypes in terms of conditions needed for the spread of SC in mayapple populations (little or no morphological change would be needed to ensure within‐flower selfing). Seed set from putative SC genotypes appeared to be low enough to prevent them from replacing SI genotypes, even in the face of infrequent pollinator visits.

Expression of self-incompatibility and fertility of Brassica napus L. resynthesized by interspecific somatic hybridization

Brassica napus is a natural allotetraploid derived from the diploid species B. rapa L. (syn. campestris L.) and B. oleracea L. Somatic hybrids synthesized from highly heterozygous lines of these two diploid species were evaluated for fertility. The hybrids were obtained from two fusion experiments which differed in the B. rapa full-sibling parent used as the source of protoplasts. Both B. rapa siblings were lelf-incompatible (SI) yet contained different S-alleles; the B. oleracea species parent was self-compatible (SC). Eight tetraploid hybrids examined had very high female and male fertility; eight hybrids with higher ploidy had low fertility. Hybrids derived from one B. rapa sibling were self-incompatible, whereas those derived from the other B. rapa sibling were fully self-compatible. These data suggest that the different S-alleles of each B. rapa sibling displayed varying penetrance relative to the SC of the B. oleracea parent when combined in B. napus.

Investigation of a self-compatible mutation in Solanum tuberosum clones inhibiting S-allele activity in pollen differentially

A self-compatible (SC) mutation, identified in dihaploid lines of Solanum tuberosum, was investigated. It has previously been proposed that this mutation arose by translocation of an S-allele (S1) to a new chromosomal location. When present in pollen grains of genotype Sx, it overcomes the incompatibility reaction normally seen on styles carrying the Sx allele. However, when present in S1-bearing pollen grains, the normal incompatibility reaction on styles carrying S1 is still observed. Using probes for the potato (S. tuberosum L.) S-linked glycoprotein (SLG) genes, it is shown that no sequence derived from SLG allele S1 can be linked to the presence of the SC mutation. The polypeptide product of the SLG allele S1 is also not detectable in SC mutant lines unless the S1 allele is also present. It is concluded that the SC mutation arose in a sequence other than that encoding the SLG S1 polypeptide, either in a part of the S-locus that is distinct from the S-gene, or at a different locus, giving rise to an inhibitor.

Dichogamy, Sex Allocation, and Mating System of Campanula microdonta and C. punctata

Dichogamy and sex allocation in several populations of Campanula microdonta and C. punctata were investigated with regard to their mating systems. Duration of the staminate phase differed among the populations: staminate phase was longer in self‐compatible (SC) and largely outcrossing populations than in self‐incompatible (SI) and outcrossing populations or in SC and largely inbreeding populations. Duration of the pistillate phase among the populations was less variable than duration of the staminate phase. Male reproductive effort decreased with increase of the estimated selfing rates. Male allocation (weight ratio of androecium to gynoecium or to total flower) may be used as an indicator of the breeding system. Within each population, small flowers allocate proportionately more resources to the androecium than to the gynoecium. Among populations, SC outcrossing populations tend to produce large ovaries, and SC inbreeding populations tend to produce small ovaries.

RFLP analysis of phylogenetic relationships and genetic variation in the genus Lycopersicon

Forty single-copy, nuclear probes of known chromosomal position were used to examine restriction fragment length polymorphism in the tomato genus Lycopersion. The probes were from three libraries: one cDNA, and two genomic libraries [Symbol: see text]ne genomic made with EcoRI and the other with PstI. Total DNA from 156 plants representing eight species was cut with five different restriction enzymes and scored in 198 probe-enzyme combinations. Genetic distances between accessions (populations) and species were calculated from the resultant restriction patterns and proportion of shared bands. Accessions belonging to the same species largely clustered together, confirming their current classification. However, one mountain accession, classified as L. peruvianum var. humifusum (LA2150), was sufficiently distinct from the other accessions of L. peruvianum that it may qualify as a separate species L. esculentum and L. pimpinellifolium were the least clearly differentiated, possibly reflecting introgressive hybridization, known to have been promoted by man in recent history. Dendrograms constructed from cDNA versus genomic clones were nearly identical in their general grouping of species. The dendrograms revealed two major dichotomies in the genus: one corresponding to mating behavior [self-compatible (SC) versus self-incompatible (SI) species] and the other corresponding to fruit color (red versus green-fruited species). The ratio of withinversus between-accession diversity was much lower for SC species, indicating that most of the diversity within these species exists between populations, rather than within populations. Overall, the amount of genetic variation in the SI species far exceeded that found in SC species. This result is exemplified by the fact that more genetic variation could be found within a single accession of one of the SI species (e.g., L. peruvianum) than among all accessions tested of any one of the SC species (e.g., L. esculentum or L. pimpinellifolium). Results from this study are discussed in relationship to germ plasm collection/utilization and with regard to the use of RFLPs in tomato breeding and genetics.

Evolution of Mating Systems in Island Populations of Campanula microdonta: Pollinator Availability Hypothesis

Abstract Island populations of Campanula microdonta and mainland Honshu populations of C. punctata have several different mating systems: self‐incompatible (SI) and therefore obligately outcrossing in mainland Honshu and Oshima Island; self‐compatible (SC) and largely outcrossing in the northern islands of Toshima and Niijima; and SC and predominantly inbreeding southern ones of Miyake and Hachijo. Several features possibly associated with the mating systems are described. A hypothesis is proposed that the mean and variance of pollinator availability together with inbreeding depression could explain the observed patterns of mating system as the results of evolution.

Independence of self-compatibility and potentiality for self-pollination in peach x almond hybrids

The almond of commerce (Prunus dulcis (Mill.) D.A. Webb) is self-incompatible (SI) and requires honey-bees to effect the transfer of pollen among cultivars that flower simultaneously. Four year old trees from the F2 generation of several peach x almond hybrids were studied to determine whether self-compatibility (SC) and the potentiality for natural, i.e., abiotic, self pollination (NSP) are genetically related or are inherited independently. Both SC and the high potentiality for NSP are characteristic of peach (Prunus persica (L.) Batsch) but not almond. Forty percent of SC genotypes exhibited adequate NSP (SC, +NSP) for good fertility i.e., without insect-mediated pollination. The remaining 60% of SC genotypes (SC,-NSP) exhibited an average 61% reduction in fruit set on limbs bagged to exclude honeybees during anthesis relative to fruit set on open pollinated limbs. Our data are consistent with the concept that fertility is dependent upon the load of compatible pollen deposited on the stigma. Fruit set reduction on bagged limbs, compared with bagged and self-pollinated limbs, was presumably due to a) lack of/insufficient pollination for fertilization and/or b) post-zygotic abortion of genetically inferior recombinants. Selection following manual self-pollination may result in SC genotypes with or without the capacity for NSP. In contrast, significant fruit set on limbs enclosed during pistil receptivity necessitates that the genotype selected express both SC and the potentiality for NSP.

Self‐Compatibility/Incompatibility in Some Orchids of the Subfamily Vandoideae

AbstractSelf‐pollination of 2f species of vandaceous orchids was followed by later embryo culture carried out to determine which species are self‐compatible (SC) or incompatible (SI): 10 are SC, 1 are SI and the remaining:8 require further study. In the SI species, a few progeny could usually be recovered and these are interpreted as arising from mutation at the incompatibility locus (loci). The implications of the findings for current models of incompatibility are discussed.

Evolution of Campanula punctata Lam. in the Izu Islands: Changes of Pollinators and Evolution of Breeding Systems

Abstract The pollination and breeding systems of Campanula punctata both in the Izu Islands and the mainland (Honshu) adjacent to the islands were investigated. The predominant pollinators of campanulas are: 1) Bombus diversus in Honshu, 2) Bombus ardens and halictid bees on Oshima Island, and 3) halictid bees on the islands of Niijima, Kodzushma, and Hachijo. The absence of bumble bees except B. ardens on Oshima Island, and the abundance of halictid bees represent a kind of island effect. Flowers of the campanula in the Islands were found to be smaller than those of the mainland. This might have resulted from adaptation to the small pollinators. Pollination experiments with plants grown from seeds revealed the following differences in breeding system: 1) most of the campanulas from Honshu were highly self‐incompatible (SI) and a few partially self‐compatible (SC), 2) one half of the plants from Oshima Island were more or less SC and the remaining highly SI, 3) those from Hachijo Island were SC and potentially autogamous. The breakdown of dichogamy co‐operated with self‐compatibility in the development of self‐fertilizing ability in Hachijo plants. Several possible causes for the change in the breeding system including the change in pollinators in the Islands are discussed.

BREEDING SYSTEMS OF CENTRAL AMERICAN APHELANDRA (ACANTHACEAE)

Controlled pollinations, followed by germination studies of seeds resulting from self‐ and cross‐pollination, were carried out using plants from 12 populations of nine species of Aphelandra (Acanthaceae), a genus of neotropical shrubs and herbs. These results are combined with data from field studies of flower morphology, phenology, and pollinator relationships to estimate breeding system of each species. All species have floral morphological traits that prevent autogamy. Plants from five populations of five species experience low levels of geitonogamous pollen transfer; they produce few flowers daily and are pollinated by traplining hummingbirds. Excepting A. storkii, these plants are fully self‐compatible (SC), and seeds from selfing are as viable as crossed seeds. Aphelandra storkii is partially self‐incompatible (SI) and produces seeds from selfing that tend to germinate less successfully than crossed seeds. Plants from the remaining populations are profusely flowering shrubs, and even those pollinated by traplining hummingbirds should experience higher levels of geitonogamy. Aphelandra deppeana is pollinated by territorial hummingbirds, which should further increase the incidence of geitonogamy. All shrub species are partially SI, and two species (A. leonardii and A. sinclairiana) show significant reduced germination of selfed vs. crossed seeds. The breeding system of these species is thus modified by postpollination factors that favor the formation and maturation of outcrossed seeds. It is suggested that Aphelandra species, like other herbs and shrubs of tropical forest understory, possess a combination of breeding system traits that promote outcrossing but do not exclude geitonogamy.