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Microsporogenesis and flower development in Eucalyptus urophylla × E. tereticornis.

Yang J, Kang X - Breed. Sci. (2015)

Bottom Line: We compared microsporogenesis and flower development in Eucalyptus urophylla × E. tereticornis.The flower buds grew on the lower side of the branch and showed greater increases in diameter.Thus, the start of microsporogenesis in E. urophylla × E. tereticornis could be determined, which may be applicable to future breeding studies.

View Article: PubMed Central - PubMed

Affiliation: National Engineering Laboratory for Tree Breeding, Beijing Forestry University , Beijing 100083 , P R China ; Key Laboratory for Genetics and Breeding of Forest Trees and Ornamental Plants, Ministry of Education, Beijing Forestry University , Beijing 100083 , P R China.

ABSTRACT
We compared microsporogenesis and flower development in Eucalyptus urophylla × E. tereticornis. In this study, although microsporogenesis and cytokinesis occurred simultaneously during meiosis of pollen mother cells, we observed a strong asynchronism in different anthers from a flower bud. The developmental period of microsporogenesis in anthers originated from the long thrum before the short thrum. Flower development was also asynchronous at different locations on a branch. The flower buds grew on the lower side of the branch and showed greater increases in diameter. In addition, we observed a relationship between microsporogenesis development and flower bud diameter growth. Generally, when the pachytene stage was first observed in a small single flower bud growing on top of a flowering branch, the remaining microsporogenesis stages (from diplotene to tetrad) in the whole branch occurred over the next 5-9 days. Thus, the start of microsporogenesis in E. urophylla × E. tereticornis could be determined, which may be applicable to future breeding studies.

No MeSH data available.


Microsporogenesis in Eucalyptus urophylla × E. tereticornis. Scale bar = 10 μm. (A) Early leptotene. (B) Late leptotene. (C) Pachytene. (D) Diplotene. (E) Diakinesis. (F) Metaphase I. (G) Anaphase I. (H) Telophase I. (I) Prophase II. (J) Metaphase II. (K) Anaphase II. (L, M) Telophase II. (N) Tetrad. (O) Microspore. (P) Multiple meiotic phases were observed in one section.
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f2-65_138: Microsporogenesis in Eucalyptus urophylla × E. tereticornis. Scale bar = 10 μm. (A) Early leptotene. (B) Late leptotene. (C) Pachytene. (D) Diplotene. (E) Diakinesis. (F) Metaphase I. (G) Anaphase I. (H) Telophase I. (I) Prophase II. (J) Metaphase II. (K) Anaphase II. (L, M) Telophase II. (N) Tetrad. (O) Microspore. (P) Multiple meiotic phases were observed in one section.

Mentions: At the beginning of meiosis, pollen mother cells (PMCs) with thick cytoplasm huddled together in the anther and were difficult to separate. In the early leptotene stage (Fig. 2A), filiform chromosomes were irregularly distributed around the nucleolus where the cytoplasm was still thick. Chromosomes gradually gathered at one side of the nucleolus during the late leptotene stage (Fig. 2B), which presented as a truss. At this stage, thick and translucent callose surrounded the PMC, which separated the cells and allowed for better observation. The chromosomes continued to coarsen during the pachytene stage (Fig. 2C) and chromosomes remained entangled. During the diplotene stage (Fig. 2D), homologous chromosomes began to repel each other, although chromosome chiasmate was clearly observed. During the diakinesis stages (Fig. 2E), chromosomes were highly coagulated and 11 homologous bivalents separated equally in the cell, which facilitated chromosome counting. During metaphase I (Fig. 2F), chromosomes were neatly established along the equatorial plate. Subsequently, during anaphase I (Fig. 2G), chromosomes of homologous pairs were pulled to two ends of the cell. During telophase I (Fig. 2H), uncoiling chromosomes and some small nucleolus were observed. Prophase II (Fig. 2I) was making an appearance at the beginning of meiosis II, then two groups of chromosomes arranged at the equatorial plate during metaphase II (Fig. 2J), after which they were pulled into four corners during anaphase II (Fig. 2K). At telophase II (Fig. 2L, 2M), chromosomes uncoiled and nucleolus reappeared. Cytokinesis in E. urophylla × E. tereticornis was simultaneous and the microspore tetrads were tetrahedral (Fig. 2N, 2O).


Microsporogenesis and flower development in Eucalyptus urophylla × E. tereticornis.

Yang J, Kang X - Breed. Sci. (2015)

Microsporogenesis in Eucalyptus urophylla × E. tereticornis. Scale bar = 10 μm. (A) Early leptotene. (B) Late leptotene. (C) Pachytene. (D) Diplotene. (E) Diakinesis. (F) Metaphase I. (G) Anaphase I. (H) Telophase I. (I) Prophase II. (J) Metaphase II. (K) Anaphase II. (L, M) Telophase II. (N) Tetrad. (O) Microspore. (P) Multiple meiotic phases were observed in one section.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4430506&req=5

f2-65_138: Microsporogenesis in Eucalyptus urophylla × E. tereticornis. Scale bar = 10 μm. (A) Early leptotene. (B) Late leptotene. (C) Pachytene. (D) Diplotene. (E) Diakinesis. (F) Metaphase I. (G) Anaphase I. (H) Telophase I. (I) Prophase II. (J) Metaphase II. (K) Anaphase II. (L, M) Telophase II. (N) Tetrad. (O) Microspore. (P) Multiple meiotic phases were observed in one section.
Mentions: At the beginning of meiosis, pollen mother cells (PMCs) with thick cytoplasm huddled together in the anther and were difficult to separate. In the early leptotene stage (Fig. 2A), filiform chromosomes were irregularly distributed around the nucleolus where the cytoplasm was still thick. Chromosomes gradually gathered at one side of the nucleolus during the late leptotene stage (Fig. 2B), which presented as a truss. At this stage, thick and translucent callose surrounded the PMC, which separated the cells and allowed for better observation. The chromosomes continued to coarsen during the pachytene stage (Fig. 2C) and chromosomes remained entangled. During the diplotene stage (Fig. 2D), homologous chromosomes began to repel each other, although chromosome chiasmate was clearly observed. During the diakinesis stages (Fig. 2E), chromosomes were highly coagulated and 11 homologous bivalents separated equally in the cell, which facilitated chromosome counting. During metaphase I (Fig. 2F), chromosomes were neatly established along the equatorial plate. Subsequently, during anaphase I (Fig. 2G), chromosomes of homologous pairs were pulled to two ends of the cell. During telophase I (Fig. 2H), uncoiling chromosomes and some small nucleolus were observed. Prophase II (Fig. 2I) was making an appearance at the beginning of meiosis II, then two groups of chromosomes arranged at the equatorial plate during metaphase II (Fig. 2J), after which they were pulled into four corners during anaphase II (Fig. 2K). At telophase II (Fig. 2L, 2M), chromosomes uncoiled and nucleolus reappeared. Cytokinesis in E. urophylla × E. tereticornis was simultaneous and the microspore tetrads were tetrahedral (Fig. 2N, 2O).

Bottom Line: We compared microsporogenesis and flower development in Eucalyptus urophylla × E. tereticornis.The flower buds grew on the lower side of the branch and showed greater increases in diameter.Thus, the start of microsporogenesis in E. urophylla × E. tereticornis could be determined, which may be applicable to future breeding studies.

View Article: PubMed Central - PubMed

Affiliation: National Engineering Laboratory for Tree Breeding, Beijing Forestry University , Beijing 100083 , P R China ; Key Laboratory for Genetics and Breeding of Forest Trees and Ornamental Plants, Ministry of Education, Beijing Forestry University , Beijing 100083 , P R China.

ABSTRACT
We compared microsporogenesis and flower development in Eucalyptus urophylla × E. tereticornis. In this study, although microsporogenesis and cytokinesis occurred simultaneously during meiosis of pollen mother cells, we observed a strong asynchronism in different anthers from a flower bud. The developmental period of microsporogenesis in anthers originated from the long thrum before the short thrum. Flower development was also asynchronous at different locations on a branch. The flower buds grew on the lower side of the branch and showed greater increases in diameter. In addition, we observed a relationship between microsporogenesis development and flower bud diameter growth. Generally, when the pachytene stage was first observed in a small single flower bud growing on top of a flowering branch, the remaining microsporogenesis stages (from diplotene to tetrad) in the whole branch occurred over the next 5-9 days. Thus, the start of microsporogenesis in E. urophylla × E. tereticornis could be determined, which may be applicable to future breeding studies.

No MeSH data available.