Triple fusion of the primary endosperm nucleus as a cause of interspecific cross-incompatibility in Avena

Apomixis is a common feature of perennial plants, which occurs in ca . 60% of the British flora, but has been largely ignored by reproductive theoreticians. Successful individuals may cover huge areas, and live to great ages, favoured by ‘symmetrical’ selection. Apomixis is favoured by colonizing modes, for instance post–glacially. Despite its theoretical advantages, apomixis usually coexists with sexuality, suggesting ‘hidden’ disadvantages. Agamospermy (apomixis by seed) is relatively uncommon, but gains from the attributes of the seed. It pays agamospermy genes, which discourage recombination, to form co–adapted linkage groups, so that they become targets for disadvantageous recessive mutant accumulation. Consequently, agamospermy genes cannot succeed in diploids and agamosperms are hybrid and highly heterotic. Agamospermous endosperm may suffer from genomic imbalance, so that nutritious ovules, which can support embryos without endosperm, may be preadapted for agamospermy. When primary endosperm nucleus fertilization (‘pseudogamy’) continues as a requirement for many aposporous agamosperms, selfing sex becomes preadaptive and archesporial sex remains an option. Apomictic populations can be quite variable although apomictic families are much less variable than sexuals. Only in some diplosporous species does sex disappear completely, and in those species some release of variability may persist through somatic recombination. The search for an agamospermy gene suitable for genetic modification should target fertile sexuals with a single localized agamospermy ( A ) gene, which therefore lack a genetic load. The A gene should coexist alongside sexuality, so that it would be easy to select seedlings of sexual and asexual origins. Plants with sporophytic agamospermy provide all these attributes.

Fecundation and Formation of the Primary Endosperm Nucleus in Certain Liliaceae

Botanical Gazette ◽

10.1086/332320 ◽

1918 ◽

Vol 66 (2) ◽

pp. 143-161 ◽

Cited By ~ 4

Author(s):

Mildred Nothnagel

Keyword(s):

Endosperm Nucleus ◽

Primary Endosperm Nucleus

EMBRYOLOGY OF INTERSPECIFIC CROSSES IN MELILOTUS

Canadian Journal of Botany ◽

10.1139/b54-041 ◽

1954 ◽

Vol 32 (3) ◽

pp. 447-465 ◽

Cited By ~ 12

Author(s):

John Edward Ross Greenshields

Keyword(s):

Germ Plasm ◽

Female Parent ◽

Early Embryo ◽

Endosperm Nucleus ◽

Interspecific Crosses ◽

Primary Endosperm Nucleus ◽

Embryo Abortion ◽

Advanced Embryo ◽

Essentially Normal ◽

The Cross

Twelve species of Melilotus were intercrossed and the embryology of the hybrids was studied. The species involved in this study are M. alba, M. officinalis, M. suaveolens, M. polonica, M. dentata, M. altissima, M. hirsutus, M. taurica, M. messanensis, M. italica, M. sulcat, and M. speciosa. Among partially compatible crosses, M. officinalis × M. alba produces the most advanced embryo. Growth of the embryo proceeds normally until about eight days, and more slowly thereafter until the 12th or 13th day, when growth is completely inhibited and the embryo aborts. The reciprocal M. alba × M. officinalis embryo does not grow as large or differentiate as much before aborting by the 11th day. Other crosses, including M. officinalis × M. suaveolens and M. alba × M. messanensis form a normal proembryo that grows slowly to about the sixth day. The proembryo then loses polarity, organ development becomes abnormal, and the ovule aborts about the 12th day. Aborted embryos are also produced in the cross, M. alba × M. dentata. Reciprocal crosses of M. suaveolens and M. altissima and M. altissima × M. polonica produce essentially normal embryos up to eight days. These crosses may be sources of economically important germ plasm. Crosses of M. altissima × M. alba and M. italica × M. altissima exhibit early embryo abortion. The suspensor becomes necrotic in four or five days and the proembryo floats into the ovule cavity, which contains abundant noncellular endosperm. In the cross M. officinalis × M. altissima, neither the zygote nor the primary endosperm nucleus divides. When M. altissima is used as the female parent, the zygote does not divide but the endosperm proliferates. In the cross, M. italica × M. officinalis, neither the zygote nor the endosperm divides. Embryos of M. italica × M. sulcata grow for four or five days, but the primary endosperm nucleus does not divide. The hybrid seed of M. alba × M. suaveolens weighs less than seed of either parent. Although developing ovules are smaller than those of M. suaveolens × M. alba, the embryo of the former is much larger and more differentiated, and endosperm is more abundant. This relationship between these two compatible species is of particular theoretical interest. Although many of the crosses do not mature viable seed, some embryos develop normally to a point where they would be worthy subjects for culture on nutrient agar.

Fertilisation of polar nuclei and formation of early endosperms in Dendrobium catenatum: evidence for the second fertilisation in Orchidaceae

Australian Journal of Botany ◽

10.1071/bt17211 ◽

2018 ◽

Vol 66 (4) ◽

pp. 354 ◽

Cited By ~ 1

Author(s):

Yong Chen ◽

Chu Zhang ◽

Xiao-feng Wang ◽

Cheng-qi Ao

Keyword(s):

Embryo Development ◽

Endosperm Development ◽

Endosperm Nucleus ◽

Primary Endosperm Nucleus ◽

Section Technique ◽

Embryo Stage ◽

New Evidence

Whether the second fertilisation, i.e. fertilisation of polar nuclei, or fusion of the second sperm with polar nuclei occurs in Orchidaceae has long been controversial because of lack of evidence. In the present study, we observed fusion and fertilisation of polar nuclei and formation of early endosperms in the orchid Dendrobium catenatum Lindl., by using a resin-embedded section technique. As the product of the second fertilisation, the primary endosperm nucleus (fertilised polar nuclei) can last until the global embryo stage, indicating that initiation of endosperm development and that of embryo development were fully asynchronous. The present study demonstrated the occurrence of the second fertilisation in D. catenatum by providing lines of new evidence.

Capsella Embryogenesis: The Central Cell

Journal of Cell Science ◽

10.1242/jcs.12.3.741 ◽

1973 ◽

Vol 12 (3) ◽

pp. 741-763

Author(s):

PATRICIA SCHULZ ◽

W. A. JENSEN

Keyword(s):

Central Cell ◽

Endosperm Nucleus ◽

Binucleate Cell ◽

Cell Cytoplasm ◽

Primary Endosperm Nucleus ◽

Structural Reorganization ◽

Nucleolar Material ◽

And Function ◽

Relationship Of ◽

The Relationship

The central cell is the binucleate cell of the angiosperm megagametophyte which contains the polar nuclei and participates in double fertilization. The structure of the mature central cell, the fusion of the polar nuclei and the primary endosperm nucleus were studied with the electron microscope. The central cell cytoplasm appears very active and has an extensive ER, many mitochondria, dictyosomes, microbodies, polysomes, chloroplasts with well developed grana and starch and lipid reserves. A single, giant mitochondrion appears in the cytoplasm near the polar nuclei at the time of fertilization, but its origin, fate and function are not known. Cytoplasmic aggregates of dense, granular material are associated with the primary endosperm nucleus and structurally resemble the nucleolus and similar aggregates in the nucleoplasm. It is suggested that these cytoplasmic perinuclear bodies may represent extruded nucleolar material. The central cell cytoplasm does not undergo any notable structural reorganization as a result of fertilization. The relationship of the central cell to the other cells of the mature megagametophyte and its possible role in embryogenesis is discussed.

Amino Acid Percentages in the Groat‐Protein of Oat Lines from an Interspecific Cross 1

Crop Science ◽

10.2135/cropsci1972.0011183x001200030042x ◽

1972 ◽

Vol 12 (3) ◽

pp. 391-392 ◽

Cited By ~ 3

Author(s):

A. R. Campbell ◽

K. J. Frey

Keyword(s):

Amino Acid ◽

Interspecific Cross

A Simple Sequence Repeat-Based Linkage Map of Barley

Genetics ◽

10.1093/genetics/156.4.1997 ◽

2000 ◽

Vol 156 (4) ◽

pp. 1997-2005 ◽

Cited By ~ 3

Author(s):

L Ramsay ◽

M Macaulay ◽

S degli Ivanissevich ◽

K MacLean ◽

L Cardle ◽

...

Keyword(s):

Simple Sequence Repeat ◽

Interspecific Cross ◽

Hordeum Spontaneum ◽

Doubled Haploid Population ◽

Sequence Repeat ◽

Genomic Libraries ◽

Barley Cultivars ◽

Multiple Loci ◽

Marker Distribution ◽

Simple Sequence

AbstractA total of 568 new simple sequence repeat (SSR)-based markers for barley have been developed from a combination of database sequences and small insert genomic libraries enriched for a range of short simple sequence repeats. Analysis of the SSRs on 16 barley cultivars revealed variable levels of informativeness but no obvious correlation was found with SSR repeat length, motif type, or map position. Of the 568 SSRs developed, 242 were genetically mapped, 216 with 37 previously published SSRs in a single doubled-haploid population derived from the F1 of an interspecific cross between the cultivar Lina and Hordeum spontaneum Canada Park and 26 SSRs in two other mapping populations. A total of 27 SSRs amplified multiple loci. Centromeric clustering of markers was observed in the main mapping population; however, the clustering severity was reduced in intraspecific crosses, supporting the notion that the observed marker distribution was largely a genetical effect. The mapped SSRs provide a framework for rapidly assigning chromosomal designations and polarity in future mapping programs in barley and a convenient alternative to RFLP for aligning information derived from different populations. A list of the 242 primer pairs that amplify mapped SSRs from total barley genomic DNA is presented.

Genetic Screens for Factors Involved in the Notum Bristle Loss of Interspecific Hybrids Between Drosophila melanogaster and D. simulans

Genetics ◽

10.1093/genetics/156.1.269 ◽

2000 ◽

Vol 156 (1) ◽

pp. 269-282

Author(s):

Toshiyuki Takano-Shimizu

Keyword(s):

Drosophila Melanogaster ◽

Interspecific Cross ◽

Species Variation ◽

Genetic Screens ◽

Pure Species ◽

Epistatic Interactions ◽

X Chromosomes ◽

Powerful Means ◽

Different Populations ◽

Deficiency Screening

Abstract Interspecific cross is a powerful means to uncover hidden within- and between-species variation in populations. One example is a bristle loss phenotype of hybrids between Drosophila melanogaster and D. simulans, although both the pure species have exactly the same pattern of bristle formation on the notum. There exists a large amount of genetic variability in the simulans populations with respect to the number of missing bristles in hybrids, and the variation is largely attributable to simulans X chromosomes. Using nine molecular markers, I screened the simulans X chromosome for genetic factors that were responsible for the differences between a pair of simulans lines with high (H) and low (L) missing bristle numbers. Together with duplication-rescue experiments, a single major quantitative locus was mapped to a 13F–14F region. Importantly, this region accounted for most of the differences between H and L lines in three other independent pairs, suggesting segregation of H and L alleles at the single locus in different populations. Moreover, a deficiency screening uncovered several regions with factors that potentially cause the hybrid bristle loss due to epistatic interactions with the other factors.

Integration of high-density genetic mapping with transcriptome analysis uncovers numerous agronomic QTL and reveals candidate genes for the control of tillering in sorghum

G3 Genes|Genome|Genetics ◽

10.1093/g3journal/jkab024 ◽

2021 ◽

Author(s):

Rajanikanth Govindarajulu ◽

Ashley N Hostetler ◽

Yuguo Xiao ◽

Srinivasa R Chaluvadi ◽

Margarita Mauro-Herrera ◽

...

Keyword(s):

Agronomic Traits ◽

Interspecific Cross ◽

Crop Improvement ◽

Differentially Expressed ◽

Plant Domestication ◽

Sorghum Propinquum ◽

Ril Population ◽

Trait Locus ◽

Genomic Regions ◽

Low Coverage

Abstract Phenotypes such as branching, photoperiod sensitivity, and height were modified during plant domestication and crop improvement. Here, we perform quantitative trait locus (QTL) mapping of these and other agronomic traits in a recombinant inbred line (RIL) population derived from an interspecific cross between Sorghum propinquum and Sorghum bicolor inbred Tx7000. Using low-coverage Illumina sequencing and a bin-mapping approach, we generated ∼1920 bin markers spanning ∼875 cM. Phenotyping data were collected and analyzed from two field locations and one greenhouse experiment for six agronomic traits, thereby identifying a total of 30 QTL. Many of these QTL were penetrant across environments and co-mapped with major QTL identified in other studies. Other QTL uncovered new genomic regions associated with these traits, and some of these were environment-specific in their action. To further dissect the genetic underpinnings of tillering, we complemented QTL analysis with transcriptomics, identifying 6189 genes that were differentially expressed during tiller bud elongation. We identified genes such as Dormancy Associated Protein 1 (DRM1) in addition to various transcription factors that are differentially expressed in comparisons of dormant to elongating tiller buds and lie within tillering QTL, suggesting that these genes are key regulators of tiller elongation in sorghum. Our study demonstrates the usefulness of this RIL population in detecting domestication and improvement-associated genes in sorghum, thus providing a valuable resource for genetic investigation and improvement to the sorghum community.

Reproductive development in two species of Darwinia Rudge (Myrtaceae)

Australian Journal of Botany ◽

10.1071/bt9690215 ◽

1969 ◽

Vol 17 (2) ◽

pp. 215 ◽

Cited By ~ 8

Author(s):

N Prakash

Keyword(s):

Embryo Sac ◽

Pollen Grains ◽

Reproductive Development ◽

Outer Zone ◽

Mature Embryo ◽

Globular Embryo ◽

Primary Endosperm Nucleus ◽

Oil Glands ◽

Polygonum Type ◽

History Of

In Darwinia the floral parts are differentiated in a "calyx-orolla-gynoeciumandroecium" sequence. In individual buds stages of microsporogenesis markedly precede corresponding stages of megasporogenesis. The anther is tetrasporangiate with all sporangia lying in one plane. The secretory tapetum is one- to three-layered within the same microsporangium and a large number of Ubisch bodies are formed. The anthers dehisce by minute lateral pores and an ingenious mechanism helps disperse the twocelled pollen grains. A basal placenta in the single loculus of the ovary bears four ovules in D. micropetala and two in D. fascicularis. In both species, however, only one ovule is functional after fertilization. The fully grown ovules are anatropous, crassinucellar, and bitegmic; the inner integument forms the micropyle. The parietal tissue is most massive at the completion of megasporogenesis but is progressively destroyed later. The embryo sac follows the Polygonum type of developnlent and when mature is five-nucleate, the three antipodals being ephemeral. Following fertilization, the primary endosperm nucleus divides before the zygote. Subsequent nuclear divisions in the endosperm mother cell are synchronous and lead to a free-nuclear endosperm which becomes secondarily cellular, starting from the micropylar end at the time the globular embryo assumes an elongated shape. Embryogeny is irregular and the mature embryo is straight with a massive radicle and a hypocotyl which terminates in two barely recognizable cotyledons. Sometimes the minute cotyledons are borne on a narrow neck-like extension of the hypocotyl. A suspensor is absent. Both integuments are represented in the seed coat and only the outer layer of the outer and the inner layer of the inner integuments, with their thick-walled tanniniferous cells, remain in the fully grown seed. The ovary wall is demarcated into an outer zone containing oil glands surrounded by cells containing a tannin-like substance and an inner zone of spongy parenchyma. In the fruit this spongy zone breaks down completely but the outer zone is retained. The two species of Darwinia, while closely resembling each other in their embryology, differ significantly from other Myrtaceae. However, no taxonomic conclusions are drawn at this stage, pending enquiry into the life history of other members of the tribe Chamaelaucieae.