School of Life Sciences and Biotechnology , Shanghai Jiao Tong University, Shanghai 200240, China.
Plant Physiol. 2011 Jun;156(2):615-30. doi: 10.1104/pp.111.175760. Epub 2011 Apr 22.
In higher plants, timely degradation of tapetal cells, the innermost sporophytic cells of the anther wall layer, is a prerequisite for the development of viable pollen grains. However, relatively little is known about the mechanism underlying programmed tapetal cell development and degradation. Here, we report a key regulator in monocot rice (Oryza sativa), PERSISTANT TAPETAL CELL1 (PTC1), which controls programmed tapetal development and functional pollen formation. The evolutionary significance of PTC1 was revealed by partial genetic complementation of the homologous mutation MALE STERILITY1 (MS1) in the dicot Arabidopsis (Arabidopsis thaliana). PTC1 encodes a PHD-finger (for plant homeodomain) protein, which is expressed specifically in tapetal cells and microspores during anther development in stages 8 and 9, when the wild-type tapetal cells initiate a typical apoptosis-like cell death. Even though ptc1 mutants show phenotypic similarity to ms1 in a lack of tapetal DNA fragmentation, delayed tapetal degeneration, as well as abnormal pollen wall formation and aborted microspore development, the ptc1 mutant displays a previously unreported phenotype of uncontrolled tapetal proliferation and subsequent commencement of necrosis-like tapetal death. Microarray analysis indicated that 2,417 tapetum- and microspore-expressed genes, which are principally associated with tapetal development, degeneration, and pollen wall formation, had changed expression in ptc1 anthers. Moreover, the regulatory role of PTC1 in anther development was revealed by comparison with MS1 and other rice anther developmental regulators. These findings suggest a diversified and conserved switch of PTC1/MS1 in regulating programmed male reproductive development in both dicots and monocots, which provides new insights in plant anther development.
在高等植物中，绒毡层细胞（花药壁内层的孢子体细胞）的适时降解是发育出有活力花粉粒的前提条件。然而，对于程序性绒毡层细胞发育和降解的机制，我们知之甚少。在这里，我们报道了单子叶水稻（Oryza sativa）中的一个关键调控因子——持久绒毡层细胞 1（PTC1），它控制着程序性绒毡层的发育和有功能的花粉形成。通过部分遗传互补二倍体拟南芥（Arabidopsis thaliana）中的同源突变雄性不育 1（MS1），揭示了 PTC1 的进化意义。PTC1 编码一个 PHD 指（植物同源结构域）蛋白，它在花药发育的 8 期和 9 期（野生型绒毡层细胞开始典型的凋亡样细胞死亡时）特异性表达于绒毡层细胞和小孢子中。尽管 ptc1 突变体在缺乏绒毡层 DNA 片段化、绒毡层退化延迟、花粉壁形成异常和小孢子发育中止方面表现出与 ms1 相似的表型，但 ptc1 突变体表现出一种以前未报道的不受控制的绒毡层增殖和随后发生坏死样绒毡层死亡的表型。微阵列分析表明，2417 个绒毡层和小孢子表达的基因，主要与绒毡层发育、退化和花粉壁形成有关，在 ptc1 花药中表达发生了改变。此外，通过与 MS1 和其他水稻花药发育调控因子的比较，揭示了 PTC1 在花药发育中的调控作用。这些发现表明，PTC1/MS1 在调控双子叶植物和单子叶植物程序性雄性生殖发育方面具有多样化和保守的开关作用，为植物花药发育提供了新的见解。
