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Aberrant Meiotic Prophase I Leads to Genic Male Sterility in the Novel TE5A Mutant of Brassica napus

View Article: PubMed Central - PubMed

ABSTRACT

Genic male sterility (GMS) has already been extensively utilized for hybrid rapeseed production. TE5A is a novel thermo-sensitive dominant GMS line in Brassica napus, however, its mechanisms of GMS remain largely unclear. Histological and Transmission electron microscopy (TEM) analyses of anthers showed that the male gamete development of TE5A was arrested at meiosis prophase I. EdU uptake of S-phase meiocytes revealed that the TE5A mutant could accomplish DNA replication, however, chromosomal and fluorescence in situ hybridization (FISH) analyses of TE5A showed that homologous chromosomes could not pair, synapse, condense and form bivalents. We then analyzed the transcriptome differences between young floral buds of sterile plants and its near-isogenic fertile plants through RNA-Seq. A total of 3,841 differentially expressed genes (DEGs) were obtained, some of which were associated with homologous chromosome behavior and cell cycle control during meiosis. Dynamic expression changes of selected candidate DEGs were then analyzed at different anther developmental stages. The present study not only demonstrated that the TE5A mutant had defects in meiotic prophase I via detailed cytological analysis, but also provided a global insight into GMS-associated DEGs and elucidated the mechanisms of GMS in TE5A through RNA-Seq.

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Male meiosis in fertile and sterile pollen mother cells (PMCs) prepared using the spreading technique and stained with DAPI.(A–F), meiosis in fertile PMCs; (G–J), meiosis in sterile PMCs; (A,G), leptotene. several bright stained chromatin centers were visible; (B,H), zygotene; (C) wild-type fertile pachytene showing full chromosome synapsis; (D) fertile diakinesis showing moderately condensed, unaligned bivalents; (E) telophase I, dyads were formed; (F) telophase II, tetrads were formed; (I) arrangement of chromosomes was disordered, and chromosomes formed the crescent-like structure; (J) the final arrested PMCs. Chromosomes remain together as a diffused mass. Neither meiosis I nor meiosis II is completed in these MMCs, showing meiosis being completely arrested. Scale bars = 5 μm.
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f4: Male meiosis in fertile and sterile pollen mother cells (PMCs) prepared using the spreading technique and stained with DAPI.(A–F), meiosis in fertile PMCs; (G–J), meiosis in sterile PMCs; (A,G), leptotene. several bright stained chromatin centers were visible; (B,H), zygotene; (C) wild-type fertile pachytene showing full chromosome synapsis; (D) fertile diakinesis showing moderately condensed, unaligned bivalents; (E) telophase I, dyads were formed; (F) telophase II, tetrads were formed; (I) arrangement of chromosomes was disordered, and chromosomes formed the crescent-like structure; (J) the final arrested PMCs. Chromosomes remain together as a diffused mass. Neither meiosis I nor meiosis II is completed in these MMCs, showing meiosis being completely arrested. Scale bars = 5 μm.

Mentions: To more precisely detect the gametophyte development defects in TE5A, we examined chromosome spreads from different stages of meiosis in the wild-type and the TE5A mutant. For wild-type meiosis, chromosomes condensed and appeared as thin threads in the nucleus at leptotene, and several bright stained chromatin centers were visible (Fig. 4A), which was followed by a progression of recombination and initiation of synapsis between chromosomes during the zygotene phase (Fig. 4B) and full synapsis of homologous chromosomes during the pachytene phase (Fig. 4C). At diakinesis, homologous chromosomes underwent desynapsis and further condensation, thereby forming bivalents (Fig. 4D). Homologous chromosomes moved to opposite poles with their separation from each other at telophase I (Fig. 4E). Subsequently, tetrads were formed during telophase II (Fig. 4F).


Aberrant Meiotic Prophase I Leads to Genic Male Sterility in the Novel TE5A Mutant of Brassica napus
Male meiosis in fertile and sterile pollen mother cells (PMCs) prepared using the spreading technique and stained with DAPI.(A–F), meiosis in fertile PMCs; (G–J), meiosis in sterile PMCs; (A,G), leptotene. several bright stained chromatin centers were visible; (B,H), zygotene; (C) wild-type fertile pachytene showing full chromosome synapsis; (D) fertile diakinesis showing moderately condensed, unaligned bivalents; (E) telophase I, dyads were formed; (F) telophase II, tetrads were formed; (I) arrangement of chromosomes was disordered, and chromosomes formed the crescent-like structure; (J) the final arrested PMCs. Chromosomes remain together as a diffused mass. Neither meiosis I nor meiosis II is completed in these MMCs, showing meiosis being completely arrested. Scale bars = 5 μm.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC5037387&req=5

f4: Male meiosis in fertile and sterile pollen mother cells (PMCs) prepared using the spreading technique and stained with DAPI.(A–F), meiosis in fertile PMCs; (G–J), meiosis in sterile PMCs; (A,G), leptotene. several bright stained chromatin centers were visible; (B,H), zygotene; (C) wild-type fertile pachytene showing full chromosome synapsis; (D) fertile diakinesis showing moderately condensed, unaligned bivalents; (E) telophase I, dyads were formed; (F) telophase II, tetrads were formed; (I) arrangement of chromosomes was disordered, and chromosomes formed the crescent-like structure; (J) the final arrested PMCs. Chromosomes remain together as a diffused mass. Neither meiosis I nor meiosis II is completed in these MMCs, showing meiosis being completely arrested. Scale bars = 5 μm.
Mentions: To more precisely detect the gametophyte development defects in TE5A, we examined chromosome spreads from different stages of meiosis in the wild-type and the TE5A mutant. For wild-type meiosis, chromosomes condensed and appeared as thin threads in the nucleus at leptotene, and several bright stained chromatin centers were visible (Fig. 4A), which was followed by a progression of recombination and initiation of synapsis between chromosomes during the zygotene phase (Fig. 4B) and full synapsis of homologous chromosomes during the pachytene phase (Fig. 4C). At diakinesis, homologous chromosomes underwent desynapsis and further condensation, thereby forming bivalents (Fig. 4D). Homologous chromosomes moved to opposite poles with their separation from each other at telophase I (Fig. 4E). Subsequently, tetrads were formed during telophase II (Fig. 4F).

View Article: PubMed Central - PubMed

ABSTRACT

Genic male sterility (GMS) has already been extensively utilized for hybrid rapeseed production. TE5A is a novel thermo-sensitive dominant GMS line in Brassica napus, however, its mechanisms of GMS remain largely unclear. Histological and Transmission electron microscopy (TEM) analyses of anthers showed that the male gamete development of TE5A was arrested at meiosis prophase I. EdU uptake of S-phase meiocytes revealed that the TE5A mutant could accomplish DNA replication, however, chromosomal and fluorescence in situ hybridization (FISH) analyses of TE5A showed that homologous chromosomes could not pair, synapse, condense and form bivalents. We then analyzed the transcriptome differences between young floral buds of sterile plants and its near-isogenic fertile plants through RNA-Seq. A total of 3,841 differentially expressed genes (DEGs) were obtained, some of which were associated with homologous chromosome behavior and cell cycle control during meiosis. Dynamic expression changes of selected candidate DEGs were then analyzed at different anther developmental stages. The present study not only demonstrated that the TE5A mutant had defects in meiotic prophase I via detailed cytological analysis, but also provided a global insight into GMS-associated DEGs and elucidated the mechanisms of GMS in TE5A through RNA-Seq.

No MeSH data available.


Related in: MedlinePlus