Johnston Robyn, Candela Héctor, Hake Sarah, Foster Toshi
Department of Plant Biology, Cornell University, Ithaca, New York, USA.
Genesis. 2010 Jul;48(7):416-23. doi: 10.1002/dvg.20622.
Plant lateral organs, such as leaves, have three primary axes of growth-proximal-distal, medial--lateral and adaxial-abaxial (dorsal-ventral). Although most leaves are planar, modified leaf forms, such as the bikeeled grass prophyll, can be found in nature. A detailed examination of normal prophyll development indicates that polarity is established differently in the keels than in other parts of the prophyll. Analysis of the maize HD-ZIPIII gene rolled leaf1 (rld1) suggests that altered expression patterns are responsible for keel outgrowth. Recessive mutations in the maize (Zea mays) KANADI (KAN) gene milkweed pod1 (mwp1), which promotes abaxial cell identity, strongly affect development of the prophyll and silks (fused carpels). The prophyll is reduced to two unfused midribs and the silks are narrow and misshapen. Our data indicate that the prophyll and other fused organs are particularly sensitive to disruptions in adaxial-abaxial polarity. In addition, lateral and proximal-distal growth of most lateral organs is reduced in the mwp1-R mutant, supporting a role for the adaxial-abaxial boundary in promoting growth along both axes. We propose that the adaxial-abaxial patterning mechanism has been co-opted during evolution to generate diverse organ morphologies.
植物的侧生器官，如叶子，具有三个主要的生长轴——近轴-远轴、中轴-侧轴和近轴-远轴（背侧-腹侧）。尽管大多数叶子是扁平的，但自然界中也能发现一些形态各异的叶子，比如双龙骨状的禾本科前叶。对正常前叶发育的详细研究表明，龙骨部位的极性建立方式与前叶其他部分不同。对玉米HD-ZIPIII基因卷叶1（rld1）的分析表明，表达模式的改变导致了龙骨的生长。玉米（Zea mays）KANADI（KAN）基因乳草荚1（mwp1）的隐性突变会强烈影响前叶和花丝（融合心皮）的发育，该基因促进远轴细胞特性。前叶退化为两条未融合的中脉，花丝变窄且形状异常。我们的数据表明，前叶和其他融合器官对近轴-远轴极性的破坏尤为敏感。此外，mwp1-R突变体中大多数侧生器官的侧轴和近轴-远轴生长都受到抑制，这支持了近轴-远轴边界在促进两个轴向上生长中的作用。我们认为，在进化过程中，近轴-远轴模式形成机制被用于产生多样的器官形态。
