Meiotic anomalies in hybrids between wheat and apomictic Elymus rectisetus (Nees in Lehm) A Love & Conner
Meiotic anomalies in hybrids between wheat and apomictic Elymus rectisetus (Nees in Lehm) A Love & Conner
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DOI：
10.2135/cropsci1997.0011183x003700030005x
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发表时间：
1997-05-01
期刊：
影响因子：
2.3
通讯作者：
Wang, RRC
中科院分区：
文献类型：
--
作者：
Peel, MD;Carman, JG;Wang, RRC
用普通小麦(Triticum aestivum L.，2n=6x=42，AABBDD)与产生双孢子和产生2n花粉的直穗披碱草(Elymus recegsetus，2n=6x=42，StYYWW)杂交，获得了4个B-III杂种(2n=9x=63，ABDStYYWW)，确定了父本是否也发生无融合生殖和2n花粉形成。雌蕊仅仅被清除，以便用紫外显微镜观察，并用干涉对比显微镜重新清理，以进行细胞学观察。多数大孢子母细胞(MMCs)的胼胝质荧光是典型的有性种。这些都被归类为性行为。在减数分裂前期采集的4.7%的雌蕊中，观察到异常伸长的MMCs，其壁上没有胼胝质。这些特征是许多无融合生殖母细胞的典型特征。柱花草花粉母细胞(PMC)的失合和有丝分裂始终先于未减数的花粉形成。虽然观察到以下减数分裂异常现象：(I)不完全联会，染色体聚集到几个极，多个分裂形成四到八个不平衡的小孢子，以及(Ii)不完全联会，形成后期I落后的小孢子，第二次分裂导致四个带有微核的不平衡小孢子，小麦单倍体促进同源直立小麦染色体之间的PMC减数分裂配对(尽管异常)，并普遍抑制无融合减数分裂，也通过加强减数分裂。双孢子形成的原因可能是来自一个基因组的胚囊信号的表达与另一个基因组的大孢子发生信号一起早熟表达。如果这是正确的，成功地诱导小麦的无融合生殖可能需要转移具有适当程度生殖异步性的外来基因盒。
Four B-III hybrids (2n = 9x = 63, ABDStStYYWW) were obtained between wheat (Triticum aestivum L., 2n = 6x = 42, AABBDD) and a diplosporic and 2n-pollen-producing Elymus rectisetus (2n = 6x = 42, StStYYWW) accession, We determined whether apomeiosis and 2n pollen formation, which occur in the male parent, also occur in the Fill hybrids. Pistils mere cleared for UV microscopy of callose and recleared for cytological observations using interference contrast microscopy. Callose fluorescence from most megaspore mother cells (MMCs) was typical of sexual species. These were classified as sexual. Abnormally elongated MMCs with walls devoid of callose were observed in 4.7% of pistils collected at meiotic prophase. These traits are typical of many apomeiotic MMCs in E. rectisetus. Asynapsis followed by mitosis in pollen mother cells (PMCs) consistently preceded unreduced pollen formation in E. rectisetus. This was not observed in the Fill hybrids, though the following meiotic anomalies were observed: (i) asynapsis, aggregation of chromosomes to several poles, and multiple divisions to form four to eight unbalanced microspores, and (ii) incomplete synapsis, formation of anaphase I laggards, and a second division resulting in four unbalanced microspores with micronuclei, The wheat haplome enforced PMC meiotic pairing (albeit abnormal) among homologous E. rectisetus chromosomes and generally inhibited apomeiosis, also by enforcing meiosis. Diplospory may be caused by the expression of embryo sac signals from one genome precociously expressed with megasporogenesis signals from another. If this is correct, the successful induction of apomixis in wheat may require the transfer of alien gene cassettes that confer appropriate degrees of reproductive asynchrony.