Expression of SHOOT MERISTEMLESS, WUSCHEL, and ASYMMETRIC LEAVES1 Homologs in the Shoots of Podostemaceae: Implications for the Evolution of Novel Shoot Organogenesis
Expression of SHOOT MERISTEMLESS, WUSCHEL, and ASYMMETRIC LEAVES1 Homologs in the Shoots of Podostemaceae: Implications for the Evolution of Novel Shoot Organogenesis
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DOI：
10.1105/tpc.109.073189
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发表时间：
2010-07-01
期刊：
影响因子：
11.6
通讯作者：
Kato, Masahiro
中科院分区：
文献类型：
--
作者：
Katayama, Natsu;Koi, Satoshi;Kato, Masahiro
摘要水龙骨科（Podostemaceae）是一种生态和形态上都很特殊的被子植物。Tristichoideae亚科具有产生叶子的典型的茎顶端分生组织（SAMs），但Podostemoideae没有SAMs，并且新叶子在旧叶子的基部下产生。为了揭示罗汉柏科新茎器官发生进化的遗传基础，我们研究了茎发育关键调控基因的表达模式（即，三列蕨亚科和短梗蕨亚科的无茎生叶（STM）、WUSCHEL（WUS）和不对称叶1/鞘2/假叶（阿普）直系同源物。在SAM介导的Tristichoideae的芽中，像在模式植物中一样，STM和WUS直系同源物在SAM中表达。在Podostemoideae，STM和WUS直向同源物的SAM-少的芽中，在起始叶/苞片原基中表达。在老叶/苞片原基，WUS的表达消失，STM的表达成为限制在基部，而阿普的表达在远端的STM表达的互补模式。在具有正常花发育模式的Podostemoideae的生殖枝中，STM和WUS在花分生组织中表达，但在花器官中不表达，与模式植物中的模式相似。这些结果表明，Podostemoideae的叶/苞片开始作为SAM和分化成一个单一的顶端叶/苞片，导致在Podostemaceae的新的茎-叶混合器官的进化。
Podostemaceae (the river weeds) are ecologically and morphologically unusual angiosperms. The subfamily Tristichoideae has typical shoot apical meristems (SAMs) that produce leaves, but Podostemoideae is devoid of SAMs and new leaves arise below the base of older leaves. To reveal the genetic basis for the evolution of novel shoot organogenesis in Podostemaceae, we examined the expression patterns of key regulatory genes for shoot development (i.e., SHOOT MERISTEMLESS (STM), WUSCHEL (WUS), and ASYMMETRIC LEAVES1/ROUGH SHEATH2/PHANTASTICA (ARP) orthologs) in Tristichoideae and Podostemoideae. In the SAM-mediated shoots of Tristichoideae, like in model plants, STM and WUS orthologs were expressed in the SAM. In the SAM-less shoots of Podostemoideae, STM and WUS orthologs were expressed in the initiating leaf/bract primordium. In older leaf/bract primordia, WUS expression disappeared and STM expression became restricted to the basal part, whereas ARP was expressed in the distal part in a complementary pattern to STM expression. In the reproductive shoots of Podostemoideae with a normal mode of flower development, STM and WUS were expressed in the floral meristem, but not in the floral organs, similar to the pattern in model plants. These results suggest that the leaf/bract of Podostemoideae is initiated as a SAM and differentiates into a single apical leaf/bract, resulting in the evolution of novel shoot-leaf mixed organs in Podostemaceae.