EMBRYOLOGICAL STUDIES ON CROSS-INCOMPATIBILITY BETWEEN 2x AND 4x IN &lt;i&gt;BRASSICA&lt;/i&gt;

Nishiyama, Ichizo; Inomata, Nobumichi

doi:10.1266/jjg.41.27

Cited by 80 publications

(59 citation statements)

References 22 publications

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“…In endosperms from 2n=38 individuals pollinated with diploid maize, mother plants typically contributed six genomes (4M and 2Td) for a single paternal genome (1M). This corresponds to a strong distortion of the typical 2 maternal to 1 paternal genomic ratio (2m: 1p) required for normal seed development in many Angiosperms, including maize (Lin, 1984, Nishiyama andInomata, 1966) and Tripsacum, as indicated by flow cytometrical analyses in normal and imbalanced endosperms. As shown in Figure 2E, endoreduplication in endosperms derived from 4x apomicts crossed with 4x male progenitors (2n=10x, 8m: 2p) occurred precociously compared to 6x normal endosperms (4m:2p; 4x sexuals X 4x progenitors), a difference in cell cycle progression already reported in maize as a mark for maternal excess (Leblanc et al, 2002).…”

Section: Seed Developmental Abnormalities In Maize-tripsacum and Tripmentioning

confidence: 99%

Seed development and inheritance studies in apomictic maize-Tripsacum hybrids reveal barriers for the transfer of apomixis into sexual crops

Leblanc¹,

Grimanelli²,

Hernandez-Rodriguez³

et al. 2009

Int. J. Dev. Biol.

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Apomixis in plants covers a variety of cloning systems through seeds of great potential for plant breeding. Among long-standing approaches for crop improvement is the attempt to exploit wild relatives as natural, vast reservoirs for novel genetic variation. With regard to apomixis, maize possesses an apomictic wild relative, Tripsacum, which we used to produce advanced maize-Tripsacum hybrid generations. However, introgression of apomixis in maize has failed so far. In order to understand the how's and why's, we undertook characterization of seed development and inheritance studies in these materials. We show that apomictic seeds suffer from epigenetic loads. Both seed tissues, the endosperm and the embryo, displayed developmental defects resulting from imbalanced parental genomic contributions and aberrant methylation patterns, respectively. Progeny characterization of several maize-Tripsacum hybrid generations allowed significant progress toward the unraveling of the genetics of apomixis. First, chromosome deletion mapping showed that expression of apomixis requires one single Tripsacum chromosome. However, inheritance studies revealed that female gametes inheriting this segment were unequivalent carriers depending on their origin: unreduced gametes transmit a functional segment, whereas progeny derived from reduced ones reproduced sexually. Finally, chromosomal or genomic dosage variation barely affected the apomictic phenotype suggesting no dependency for ploidy in these materials. We conclude that epigenetic information imposes constraints for apomictic seed development and seems pivotal for transgenerational propagation of apomixis. The nature of the triggering mechanisms remains unknown as-yet, but it certainly explains the modest success relative to the development of apomictic maize thus far.

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Section: Seed Developmental Abnormalities In Maize-tripsacum and Tripmentioning

confidence: 99%

Seed development and inheritance studies in apomictic maize-Tripsacum hybrids reveal barriers for the transfer of apomixis into sexual crops

Leblanc¹,

Grimanelli²,

Hernandez-Rodriguez³

et al. 2009

Int. J. Dev. Biol.

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“…However, neither of these ratios are expected from any interploid crosses which may result in high rates of seed abortion in such crosses. If avoiding imbalances in genome number between different tissues within developing angiosperm seeds is as important as has been suggested (M~intzing 1930;Boyes & Thompson 1937;Stephens 1942;Brink & Cooper 1947;Nishiyama & Inomata 1966;Johnston et al 1980), then crosses between taxa at the same ploidy level would be expected to be more successful than those between ploidy levels. This has yet to be fully investigated in Actinidia.…”

Section: Implications For Breedingmentioning

confidence: 96%

Chromosome studies in someActinidiataxa and implications for breeding

McNeilage

Considine

1989

New Zealand Journal of Botany

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Microsporogenesis was studiedin eleven Actinidia taxa including A. deliciosa (kiwifruit) and in an interspecific hybrid. From chromosome counts at meiotic metaphase 1 or diakinesis, eight taxa were classified as diploids and two as tetraploids and A. deliciosa was confirmed as hexaploid. A putative 2n = 2x, 2n = 4x, 2n = 6x, x = 29 basis for the genus is therefore supported. Chromosomes in all taxa were very small. Three diploids and two polyploids analysed for meiotic pairing behaviour were all characterised by low chiasma frequencies per bivalent. Chromosome configurations other than bivalents were rare in A. arguta var. arguta (4x) and A. deliciosa (6x), indicating there may be genetic control ofchiasmata distribution in these polyploids.

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“…This phenomenon, called triploid block, was initially puzzling to plant breeders because while interploidy crosses failed, crosses between tetraploids or hexaploids (resulting in progeny with various levels of ploidy) were viable. Triploid block was eventually explained as a requirement for a correct balance of 2:1 maternal to paternal genomes in the endosperm (32)(33)(34)(35).…”

Section: Paternal and Maternal Contributions Are Not Equivalentmentioning

confidence: 99%

Seed evolution: parental conflicts in a multi-generational household

Pires

2014

BioMolecular Concepts

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Seeds are multi-generational structures containing a small embryonic plant enclosed in layers of diverse parental origins. The evolution of seeds was a pinnacle in an evolutionary trend towards a progressive retention of embryos and gametes within parental tissue. This strategy, which dates back to the first land plants, allowed an increased protection and nourishing of the developing embryo. Flowering plants took parental control one step further with the evolution of a biparental endosperm that derives from a second parallel fertilization event. The endosperm directly nourishes the developing embryo and allows not only the maternal genes, but also paternal genes, to play an active role during seed development. The appearance of an endosperm set the conditions for the manifestation of conflicts of interest between maternal and paternal genomes over the allocation of resources to the developing embryos. As a consequence, a dynamic balance was established between maternal and paternal gene dosage in the endosperm, and maintaining a correct balance became essential to ensure a correct seed development. This balance was achieved in part by changes in the genetic constitution of the endosperm and through epigenetic mechanisms that allow a differential expression of alleles depending on their parental origin. This review discusses the evolutionary steps that resulted in the appearance of seeds and endosperm, and the epigenetic and genetic mechanisms that allow a harmonious coinhabitance of multiple generations within a single seed.

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EMBRYOLOGICAL STUDIES ON CROSS-INCOMPATIBILITY BETWEEN 2x AND 4x IN <i>BRASSICA</i>

Cited by 80 publications

References 22 publications

Seed development and inheritance studies in apomictic maize-Tripsacum hybrids reveal barriers for the transfer of apomixis into sexual crops

Seed development and inheritance studies in apomictic maize-Tripsacum hybrids reveal barriers for the transfer of apomixis into sexual crops

Chromosome studies in someActinidiataxa and implications for breeding

Seed evolution: parental conflicts in a multi-generational household

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