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In Support of Winge's Theory of “Hybridization Followed by Chromosome Doubling”

Polyploidy—or chromosome doubling—plays a significant role in plant speciation and evolution. Much of the existing evidence indicates that fusion of unreduced (or 2n) gametes is the major pathway responsible for polyploid formation. In the early 1900s, a theory was put forward that the mechanism of...

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Autores principales: Tel-Zur, Noemi, Mouyal, Joseph, Zurgil, Udi, Mizrahi, Yosef
Formato: Online Artículo Texto
Lenguaje:English
Publicado: Frontiers Media S.A. 2020
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7332690/
https://www.ncbi.nlm.nih.gov/pubmed/32670340
http://dx.doi.org/10.3389/fpls.2020.00954
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author Tel-Zur, Noemi
Mouyal, Joseph
Zurgil, Udi
Mizrahi, Yosef
author_facet Tel-Zur, Noemi
Mouyal, Joseph
Zurgil, Udi
Mizrahi, Yosef
author_sort Tel-Zur, Noemi
collection PubMed
description Polyploidy—or chromosome doubling—plays a significant role in plant speciation and evolution. Much of the existing evidence indicates that fusion of unreduced (or 2n) gametes is the major pathway responsible for polyploid formation. In the early 1900s, a theory was put forward that the mechanism of “hybridization followed by chromosome doubling” would enable the survival and development of the hybrid zygote by providing each chromosome with a homolog with which to pair. However, to date there is only scant empirical evidence supporting this theory. In our previous study, interspecific-interploid crosses between the tetraploid Hylocereus megalanthus, as the female parent, and the diploid H. undatus, as the male parent, yielded only allopentaploids, allohexaploids, and 5x-and 6x-aneuploids instead of the expected allotriploids. No viable hybrids were obtained from the reciprocal cross. Since H. undatus underwent normal meiosis with regular pairing in the pollen mother cells and only reduced pollen grains were observed, the allohexaploids obtained supported the concept of “chromosome doubling.” In this work, we report ploidy level, fruit morphology, and pollen viability and diameter in a group of putative hybrids obtained from an embryo rescue procedure following controlled H. megalanthus × H. undatus crosses, with the aim to elucidate, for the first time, the timing and developmental stage of the chromosome doubling. As in our previous report, no triploids were obtained, but tetraploids, pentaploids, hexaploids, and 5x- and 6x-aneuploids were found in the regenerated plants. The tetraploids exhibited the morphological features of the maternal parent and could not be considered true hybrids. Based on our previous studies, we can assume that the pentaploids were a result of a fertilization event between one unreduced (2n) female gamete from the tetraploid H. megalanthus and a normal (n) haploid male gamete from H. undatus. All the allohexaploids obtained from the embryo rescue technique where those that regenerated from fertilized ovules 10 days after pollination (at the pro-embryo stage), showing that the chromosome doubling event occurred at a very early development stage, i.e., at the zygote stage or shortly after zygote formation. These allohexaploids thus constitute empirical evidence of “hybridization followed by chromosome doubling.”
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spelling pubmed-73326902020-07-14 In Support of Winge's Theory of “Hybridization Followed by Chromosome Doubling” Tel-Zur, Noemi Mouyal, Joseph Zurgil, Udi Mizrahi, Yosef Front Plant Sci Plant Science Polyploidy—or chromosome doubling—plays a significant role in plant speciation and evolution. Much of the existing evidence indicates that fusion of unreduced (or 2n) gametes is the major pathway responsible for polyploid formation. In the early 1900s, a theory was put forward that the mechanism of “hybridization followed by chromosome doubling” would enable the survival and development of the hybrid zygote by providing each chromosome with a homolog with which to pair. However, to date there is only scant empirical evidence supporting this theory. In our previous study, interspecific-interploid crosses between the tetraploid Hylocereus megalanthus, as the female parent, and the diploid H. undatus, as the male parent, yielded only allopentaploids, allohexaploids, and 5x-and 6x-aneuploids instead of the expected allotriploids. No viable hybrids were obtained from the reciprocal cross. Since H. undatus underwent normal meiosis with regular pairing in the pollen mother cells and only reduced pollen grains were observed, the allohexaploids obtained supported the concept of “chromosome doubling.” In this work, we report ploidy level, fruit morphology, and pollen viability and diameter in a group of putative hybrids obtained from an embryo rescue procedure following controlled H. megalanthus × H. undatus crosses, with the aim to elucidate, for the first time, the timing and developmental stage of the chromosome doubling. As in our previous report, no triploids were obtained, but tetraploids, pentaploids, hexaploids, and 5x- and 6x-aneuploids were found in the regenerated plants. The tetraploids exhibited the morphological features of the maternal parent and could not be considered true hybrids. Based on our previous studies, we can assume that the pentaploids were a result of a fertilization event between one unreduced (2n) female gamete from the tetraploid H. megalanthus and a normal (n) haploid male gamete from H. undatus. All the allohexaploids obtained from the embryo rescue technique where those that regenerated from fertilized ovules 10 days after pollination (at the pro-embryo stage), showing that the chromosome doubling event occurred at a very early development stage, i.e., at the zygote stage or shortly after zygote formation. These allohexaploids thus constitute empirical evidence of “hybridization followed by chromosome doubling.” Frontiers Media S.A. 2020-06-26 /pmc/articles/PMC7332690/ /pubmed/32670340 http://dx.doi.org/10.3389/fpls.2020.00954 Text en Copyright © 2020 Tel-Zur, Mouyal, Zurgil and Mizrahi http://creativecommons.org/licenses/by/4.0/ This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.
spellingShingle Plant Science
Tel-Zur, Noemi
Mouyal, Joseph
Zurgil, Udi
Mizrahi, Yosef
In Support of Winge's Theory of “Hybridization Followed by Chromosome Doubling”
title In Support of Winge's Theory of “Hybridization Followed by Chromosome Doubling”
title_full In Support of Winge's Theory of “Hybridization Followed by Chromosome Doubling”
title_fullStr In Support of Winge's Theory of “Hybridization Followed by Chromosome Doubling”
title_full_unstemmed In Support of Winge's Theory of “Hybridization Followed by Chromosome Doubling”
title_short In Support of Winge's Theory of “Hybridization Followed by Chromosome Doubling”
title_sort in support of winge's theory of “hybridization followed by chromosome doubling”
topic Plant Science
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7332690/
https://www.ncbi.nlm.nih.gov/pubmed/32670340
http://dx.doi.org/10.3389/fpls.2020.00954
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