Yu Lifeng, Patibanda Varun, Smith Harley M S
Department of Botany and Plant Sciences, Institute for Integrative Genome Biology, University of California, Riverside, CA 92521, USA.
Planta. 2009 Feb;229(3):693-707. doi: 10.1007/s00425-008-0867-1. Epub 2008 Dec 10.
Flowers are determinate shoots comprised of perianth and reproductive organs displayed in a whorled phyllotactic pattern. Floral organ identity genes display region-specific expression patterns in the developing flower. In Arabidopsis, floral organ identity genes are activated by LEAFY (LFY), which functions with region-specific co-regulators, UNUSUAL FLORAL ORGANS (UFO) and WUSCHEL (WUS), to up-regulate homeotic genes in specific whorls of the flower. PENNYWISE (PNY) and POUND-FOOLISH (PNF) are redundant functioning BELL1-like homeodomain proteins that are expressed in shoot and floral meristems. During flower development, PNY functions with a co-repressor complex to down-regulate the homeotic gene, AGAMOUS (AG), in the outer whorls of the flower. However, the function of PNY as well as PNF in regulating floral organ identity in the central whorls of the flower is not known. In this report, we show that combining mutations in PNY and PNF enhance the floral patterning phenotypes of weak and strong alleles of lfy, indicating that these BELL1-like homeodomain proteins play a role in the specification of petals, stamens and carpels during flower development. Expression studies show that PNY and PNF positively regulate the homeotic genes, APETALA3 and AG, in the inner whorls of the flower. Moreover, PNY and PNF function in parallel with LFY, UFO and WUS to regulate homeotic gene expression. Since PNY and PNF interact with the KNOTTED1-like homeodomain proteins, SHOOTMERISTEMLESS (STM) and KNOTTED-LIKE from ARABIDOPSIS THALIANA2 (KNAT2) that regulate floral development, we propose that PNY/PNF-STM and PNY/PNF-KNAT2 complexes function in the inner whorls to regulate flower patterning events.
花是由花被和生殖器官组成的有限生长的枝条，以轮状叶序模式排列。花器官特征基因在花的发育过程中呈现区域特异性的表达模式。在拟南芥中，花器官特征基因由LEAFY（LFY）激活，LFY与区域特异性的共调节因子异常花器官（UFO）和WUSCHEL（WUS）共同作用，上调花特定轮中的同源异型基因。PENNYWISE（PNY）和POUND-FOOLISH（PNF）是功能冗余的BELL1样同源结构域蛋白，在茎尖和花分生组织中表达。在花发育过程中，PNY与一个共抑制复合物共同作用，下调花外轮中的同源异型基因AGAMOUS（AG）。然而，PNY以及PNF在调节花中央轮花器官特征方面的功能尚不清楚。在本报告中，我们表明，PNY和PNF的双突变增强了lf y弱等位基因和强等位基因的花形态建成表型，表明这些BELL1样同源结构域蛋白在花发育过程中花瓣、雄蕊和心皮的特化中发挥作用。表达研究表明，PNY和PNF正向调节花内轮中的同源异型基因APETALA3和AG。此外，PNY和PNF与LFY、UFO和WUS平行发挥作用，调节同源异型基因的表达。由于PNY和PNF与调节花发育的KNOTTED1样同源结构域蛋白SHOOTMERISTEMLESS（STM）和拟南芥2号KNOTTED样蛋白（KNAT2）相互作用，我们提出PNY/PNF-STM和PNY/PNF-KNAT2复合物在内轮中发挥作用，调节花形态建成事件。
