Department of Plant Sciences, University of Oxford, South Parks Road, Oxford, OX1 3RB, UK.
Plant J. 2013 Aug;75(4):656-70. doi: 10.1111/tpj.12229. Epub 2013 Jun 8.
Photosynthesis underpins the viability of most ecosystems, with C4 plants that exhibit 'Kranz' anatomy being the most efficient primary producers. Kranz anatomy is characterized by closely spaced veins that are encircled by two morphologically distinct photosynthetic cell types. Although Kranz anatomy evolved multiple times, the underlying genetic mechanisms remain largely elusive, with only the maize scarecrow gene so far implicated in Kranz patterning. To provide a broader insight into the regulation of Kranz differentiation, we performed a genome-wide comparative analysis of developmental trajectories in Kranz (foliar leaf blade) and non-Kranz (husk leaf sheath) leaves of the C4 plant maize. Using profile classification of gene expression in early leaf primordia, we identified cohorts of genes associated with procambium initiation and vascular patterning. In addition, we used supervised classification criteria inferred from anatomical and developmental analyses of five developmental stages to identify candidate regulators of cell-type specification. Our analysis supports the suggestion that Kranz anatomy is patterned, at least in part, by a SCARECROW/SHORTROOT regulatory network, and suggests likely components of that network. Furthermore, the data imply a role for additional pathways in the development of Kranz leaves.
光合作用是大多数生态系统生存的基础，具有“花环”结构的 C4 植物是最高效的初级生产者。花环结构的特点是叶脉紧密排列，被两种形态上明显不同的光合细胞类型环绕。尽管花环结构多次进化，但潜在的遗传机制在很大程度上仍难以捉摸，目前只有玉米 scarecrow 基因与花环模式有关。为了更深入地了解花环分化的调控机制，我们对 C4 植物玉米的花环（叶叶片）和非花环（苞叶叶鞘）叶片的发育轨迹进行了全基因组比较分析。利用早期叶片原基基因表达的轮廓分类，我们确定了与原形成层起始和脉管模式形成相关的基因群。此外，我们还使用了从五个发育阶段的解剖学和发育分析中推断出的监督分类标准，来鉴定细胞类型特化的候选调节因子。我们的分析支持了这样的观点，即花环结构至少部分是由 SCARECROW/SHORTROOT 调控网络形成的，并提出了该网络的可能组成部分。此外，这些数据表明，在花环叶片的发育过程中，还涉及其他途径。
