Hulskamp M, Parekh N S, Grini P, Schneitz K, Zimmermann I, Lolle S J, Pruitt R E
Lehrstuhl für Entwicklungsgenetik, Tübingen, Germany.
Dev Biol. 1997 Jul 1;187(1):114-24. doi: 10.1006/dbio.1997.8554.
During male meiosis in wild-type Arabidopsis the pollen mother cell (PMC) undergoes two meiotic nuclear divisions in the absence of cell division. Only after telophase II is a wall formed which partitions the PMC into four microspores. Each microspore undergoes two subsequent mitotic divisions to produce one vegetative cell and two sperm cells in the mature pollen grain. In this paper we describe the isolation and the phenotypic characterization of mutations in the STUD (STD) gene, which is specifically required for male-specific cytokinesis after telophase II of meiosis. Although the male meiotic nuclear divisions are normal in std mutant plants, no walls are formed resulting in a tetranucleate microspore. Despite the absence of cell division in the PMC, postmeiotic development in the coenocytic microspore proceeds relatively normally, resulting in the formation of large pollen grains which contain four vegetative nuclei and up to eight sperm cells. Interestingly, these enlarged pollen grains which contain multiple vegetative nuclei and extra sperm cells behave as single male gametophytes, producing only single pollen tubes and resulting in partial male fertility in std mutant plants. Characterization of the process of pollen development and pollen function in std mutants thus reveals two different types of developmental regulation. Each of the four nuclei found in a std microspore following meiosis is capable of independently undergoing the complete mitotic cell division (including cytokinesis) which the single nucleus of a wild-type microspore would normally undertake. The ability of the four meiotic products to independently continue through mitosis does not depend on their division into separate cells, but is controlled by some subcellular component found within the coenocytic microspore. By contrast, the mature std pollen grain functions as a unit and produces only a single pollen tube despite the presence of multiple nuclei within the vegetative cell, suggesting that this process is controlled at the cellular level independently of the extra subcellular components.
在野生型拟南芥的雄配子减数分裂过程中，花粉母细胞（PMC）在不进行细胞分裂的情况下经历两次减数分裂核分裂。只有在减数第二次分裂末期之后才形成细胞壁，将PMC分隔成四个小孢子。每个小孢子随后进行两次有丝分裂，在成熟花粉粒中产生一个营养细胞和两个精细胞。在本文中，我们描述了STUD（STD）基因突变体的分离和表型特征，该基因是减数分裂后期II后雄性特异性胞质分裂所特需的。尽管std突变体植株的雄配子减数分裂核分裂正常，但未形成细胞壁，导致产生四核小孢子。尽管PMC中没有细胞分裂，但多核小孢子中的减数分裂后发育相对正常，导致形成大花粉粒，其中含有四个营养核和多达八个精细胞。有趣的是，这些含有多个营养核和额外精细胞的增大花粉粒表现为单个雄配子体，只产生单个花粉管，导致std突变体植株部分雄性可育。因此，对std突变体中花粉发育过程和花粉功能的表征揭示了两种不同类型的发育调控。减数分裂后在std小孢子中发现的四个核中的每一个都能够独立进行完整的有丝分裂细胞分裂（包括胞质分裂），而野生型小孢子的单个核通常会进行这种分裂。减数分裂的四个产物独立进行有丝分裂的能力并不取决于它们分裂成单独的细胞，而是由多核小孢子中发现的一些亚细胞成分控制。相比之下，成熟std花粉粒作为一个整体发挥作用，尽管营养细胞中有多个核，但只产生单个花粉管，这表明这个过程在细胞水平上独立于额外的亚细胞成分进行控制。
