在拟南芥的胚胎形成过程中，茎干细胞群和根干细胞群是分别在顶端和底端形成的。虽然已知PLETHORA基因起根命运主调控因子的功能，但茎命运的调控因子却不知道。
现在，Zachery Smith 和Jeff Long发现，Class III homeodomain-leucine zipper (HD-ZIP III)转录因子是胚胎顶端根命运的主调控因子，它们足以驱动胚胎根极向第二个茎极的转化。(生物谷Bioon.com)
生物谷推荐原文出处：
Nature doi:10.1038/nature08843
Control of Arabidopsis apical–basal embryo polarity by antagonistic transcription factors
Zachery R. Smith1,2 & Jeff A. Long1
1Plant Biology Laboratory, The Salk Institute for Biological Studies,
2Department of Biology, University of California San Diego, La Jolla, California 92037, USA
Plants, similarly to animals, form polarized axes during embryogenesis on which cell differentiation and organ patterning programs are orchestrated. During Arabidopsis embryogenesis, establishment of the shoot and root stem cell populations occurs at opposite ends of an apical–basal axis. Recent work has identified the PLETHORA (PLT) genes as master regulators of basal/root fate1, 2, 3, whereas the master regulators of apical/shoot fate have remained elusive. Here we show that the PLT1 and PLT2 genes are direct targets of the transcriptional co-repressor TOPLESS (TPL) and that PLT1/2 are necessary for the homeotic conversion of shoots to roots in tpl-1 mutants. Using tpl-1 as a genetic tool, we identify the CLASS III HOMEODOMAIN-LEUCINE ZIPPER (HD-ZIP III) transcription factors as master regulators of embryonic apical fate, and show they are sufficient to drive the conversion of the embryonic root pole into a second shoot pole. Furthermore, genetic and misexpression studies show an antagonistic relationship between the PLT and HD-ZIP III genes in specifying the root and shoot poles.
