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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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DAPI-stained cross-sections of anthers in both the wild-type (A–E) and the TE5A mutant (F–H). (A,F), the early PMC stage; (B,G), the meiosis stage; (C) the dyad stage; (D) the tetrad stage; (E) the microspore stage; (H) the degenerating meiocyte stage. PMC, pollen mother cell; MC, meiotic cell; Dds, dyads; Tds, tetrads; Ms, microspore; DM, degenerating meiocyte. Scale bars = 50 μm.
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f2: DAPI-stained cross-sections of anthers in both the wild-type (A–E) and the TE5A mutant (F–H). (A,F), the early PMC stage; (B,G), the meiosis stage; (C) the dyad stage; (D) the tetrad stage; (E) the microspore stage; (H) the degenerating meiocyte stage. PMC, pollen mother cell; MC, meiotic cell; Dds, dyads; Tds, tetrads; Ms, microspore; DM, degenerating meiocyte. Scale bars = 50 μm.

Mentions: To determine which step of male development was disrupted in the TE5A mutant, paraffin-cross sections of anthers from different developmental stages were analyzed through DAPI staining (Fig. 2). There are 14 well-ordered stages for anther development which is based on the morphological characteristics of Arabidopsis40. In the TE5A mutant, the early anther PMC development stage appeared normal compared to the wild-type (Fig. 2A,F). However, several differences in anther development between the wild-type and the TE5A mutant occurred after the early PMC stage. Alterations initially appeared at the MC stage, chromosomes were normally condensed into thread-like structures during wild-type meiosis, corresponding to the zygotene phase of prophase I (Fig. 2B), whereas chromosomes of the mutant were aberrantly condensed into crescent-like structure (Fig. 2G). In the later stages, in the wild-type, dyads were generated, indicating meiosis I had been completed (Fig. 2C), which was subsequently followed by the formation of tetrads (Fig. 2D) and microspores (Fig. 2E). In contrast, in the TE5A mutant, chromosomes were further condensed and eventually degenerated, and thus no dyads or tetrads were generated, thereby suggesting that the TE5A mutant failed in accomplishing meiosis I and entering meiosis II, and PMCs were arrested at meiosis I (Fig. 2H).


Aberrant Meiotic Prophase I Leads to Genic Male Sterility in the Novel TE5A Mutant of Brassica napus
DAPI-stained cross-sections of anthers in both the wild-type (A–E) and the TE5A mutant (F–H). (A,F), the early PMC stage; (B,G), the meiosis stage; (C) the dyad stage; (D) the tetrad stage; (E) the microspore stage; (H) the degenerating meiocyte stage. PMC, pollen mother cell; MC, meiotic cell; Dds, dyads; Tds, tetrads; Ms, microspore; DM, degenerating meiocyte. Scale bars = 50 μm.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

f2: DAPI-stained cross-sections of anthers in both the wild-type (A–E) and the TE5A mutant (F–H). (A,F), the early PMC stage; (B,G), the meiosis stage; (C) the dyad stage; (D) the tetrad stage; (E) the microspore stage; (H) the degenerating meiocyte stage. PMC, pollen mother cell; MC, meiotic cell; Dds, dyads; Tds, tetrads; Ms, microspore; DM, degenerating meiocyte. Scale bars = 50 μm.
Mentions: To determine which step of male development was disrupted in the TE5A mutant, paraffin-cross sections of anthers from different developmental stages were analyzed through DAPI staining (Fig. 2). There are 14 well-ordered stages for anther development which is based on the morphological characteristics of Arabidopsis40. In the TE5A mutant, the early anther PMC development stage appeared normal compared to the wild-type (Fig. 2A,F). However, several differences in anther development between the wild-type and the TE5A mutant occurred after the early PMC stage. Alterations initially appeared at the MC stage, chromosomes were normally condensed into thread-like structures during wild-type meiosis, corresponding to the zygotene phase of prophase I (Fig. 2B), whereas chromosomes of the mutant were aberrantly condensed into crescent-like structure (Fig. 2G). In the later stages, in the wild-type, dyads were generated, indicating meiosis I had been completed (Fig. 2C), which was subsequently followed by the formation of tetrads (Fig. 2D) and microspores (Fig. 2E). In contrast, in the TE5A mutant, chromosomes were further condensed and eventually degenerated, and thus no dyads or tetrads were generated, thereby suggesting that the TE5A mutant failed in accomplishing meiosis I and entering meiosis II, and PMCs were arrested at meiosis I (Fig. 2H).

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