Plant Biotechnology Institute, National Research Council Canada, Saskatoon, Saskatchewan, Canada.
Plant Cell. 2011 Dec;23(12):4348-67. doi: 10.1105/tpc.111.091777. Epub 2011 Dec 9.
The shoot and root apical meristems (SAM and RAM) formed during embryogenesis are crucial for postembryonic plant development. We report the identification of POPCORN (PCN), a gene required for embryo development and meristem organization in Arabidopsis thaliana. Map-based cloning revealed that PCN encodes a WD-40 protein expressed both during embryo development and postembryonically in the SAM and RAM. The two pcn alleles identified in this study are temperature sensitive, showing defective embryo development when grown at 22°C that is rescued when grown at 29°C. In pcn mutants, meristem-specific expression of WUSCHEL (WUS), CLAVATA3, and WUSCHEL-RELATED HOMEOBOX5 is not maintained; SHOOTMERISTEMLESS, BODENLOS (BDL) and MONOPTEROS (MP) are misexpressed. Several findings link PCN to auxin signaling and meristem function: ectopic expression of DR5(rev):green fluorescent protein (GFP), pBDL:BDL-GFP, and pMP:MP-β-glucuronidase in the meristem; altered polarity and expression of pPIN1:PIN1-GFP in the apical domain of the developing embryo; and resistance to auxin in the pcn mutants. The bdl mutation rescued embryo lethality of pcn, suggesting that improper auxin response is involved in pcn defects. Furthermore, WUS, PINFORMED1, PINOID, and TOPLESS are dosage sensitive in pcn, suggesting functional interaction. Together, our results suggest that PCN functions in the auxin pathway, integrating auxin signaling in the organization and maintenance of the SAM and RAM.
胚胎发生过程中形成的茎尖和根顶端分生组织（SAM 和 RAM）对于胚胎后植物发育至关重要。我们报告了 POPCORN（PCN）的鉴定，该基因是拟南芥胚胎发育和分生组织组织所必需的。基于图谱的克隆表明，PCN 编码一种 WD-40 蛋白，该蛋白在胚胎发育过程中以及 SAM 和 RAM 中的胚胎后表达。本研究中鉴定的两个 pcn 等位基因是温度敏感的，在 22°C 下生长时表现出胚胎发育缺陷，在 29°C 下生长时可恢复。在 pcn 突变体中，WUSCHEL（WUS）、CLAVATA3 和 WUSCHEL-RELATED HOMEOBOX5 的分生组织特异性表达不能维持；SHOOTMERISTEMLESS、BODENLOS（BDL）和 MONOPTEROS（MP）表达错误。一些发现将 PCN 与生长素信号转导和分生组织功能联系起来：DR5(rev):绿色荧光蛋白（GFP）、pBDL:BDL-GFP 和 pMP:MP-β-葡萄糖醛酸酶在分生组织中的异位表达；在发育中的胚胎的顶端域中 pPIN1:PIN1-GFP 的极性和表达发生改变；以及 pcn 突变体对生长素的抗性。bdl 突变挽救了 pcn 的胚胎致死性，表明生长素反应不当参与了 pcn 缺陷。此外，WUS、PINFORMED1、PINOID 和 TOPLESS 在 pcn 中剂量敏感，表明存在功能相互作用。总之，我们的结果表明，PCN 在生长素途径中起作用，整合了生长素信号在 SAM 和 RAM 的组织和维持中的作用。
