Olsen Odd-Arne
Department of Chemistry and Biotechnology, Agricultural University of Norway, PO. Box 5051, N-1432 Aas, Norway; e-mail:
Annu Rev Plant Physiol Plant Mol Biol. 2001 Jun;52:233-267. doi: 10.1146/annurev.arplant.52.1.233.
The endosperm develops from the central cell of the megagametophyte after introduction of the second male gamete into the diploid central cell. Of the three forms of endosperm in angiosperms, the nuclear type is prevalent in economically important species, including the cereals. Landmarks in nuclear endosperm development are the coenocytic, cellularization, differentiation, and maturation stages. The differentiated endosperm contains four major cell types: starchy endosperm, aleurone, transfer cells, and the cells of the embryo surrounding region. Recent research has demonstrated that the first two phases of endosperm occur via mechanisms that are conserved among all groups of angiosperms, involving directed nuclear migration during the coenocytic stage and anticlinal cell wall deposition by cytoplasmic phragmoplasts formed in interzones between radial microtubular systems emanating from nuclear membranes. Complete cellularization of the endosperm coenocyte is achieved through centripetal growth of cell files, extending to the center of the endosperm cavity. Key points in cell cycle control and control of the MT (microtubular) cytoskeletal apparatus central to endosperm development are discussed. Specification of cell fates in the cereal endosperm appears to occur via positional signaling; cells in peripheral positions, except over the main vascular tissues, assume aleurone cell fate. Cells over the main vascular tissue become transfer cells and all interior cells become starchy endosperm cells. Studies in maize have implicated Crinkly4, a protein receptor kinase-like molecule, in aleurone cell fate specification.
在第二个雄配子进入二倍体中央细胞后，胚乳从雌配子体的中央细胞发育而来。在被子植物胚乳的三种形式中，核型在包括谷物在内的经济重要物种中普遍存在。核型胚乳发育的标志性阶段是多核期、细胞化期、分化期和成熟期。分化的胚乳包含四种主要细胞类型：淀粉胚乳、糊粉层、转移细胞和胚周区域的细胞。最近的研究表明，胚乳发育的前两个阶段通过被子植物所有类群中保守的机制发生，包括在多核期的定向核迁移以及由源自核膜的径向微管系统之间的中间区域形成的细胞质成膜体进行的垂周细胞壁沉积。胚乳多核细胞的完全细胞化是通过细胞列的向心生长实现的，这种生长延伸到胚乳腔的中心。本文讨论了细胞周期控制以及对胚乳发育至关重要的微管（MT）细胞骨架装置控制中的关键点。谷物胚乳中的细胞命运特化似乎通过位置信号发生；除了主要维管组织上方的外周位置的细胞外，其他外周位置的细胞具有糊粉层细胞命运。主要维管组织上方的细胞成为转移细胞，所有内部细胞成为淀粉胚乳细胞。对玉米的研究表明，类受体蛋白激酶分子Crinkly4参与了糊粉层细胞命运的特化。
