Department of Biological Sciences, Graduate School of Science, The University of Tokyo, Bunkyo-ku, Tokyo 113-0033, Japan.
Am J Bot. 2013 Jun;100(6):1116-26. doi: 10.3732/ajb.1200560. Epub 2013 May 27.
On a compound leaf, leaflet primordia are repetitively formed along the apical-basal axis, with the direction varying among taxa. Why and how the directions vary among species is yet to be solved, although a change in a single factor was proposed to cause the variation. In this study, we compared two species in the Papaveraceae with different directions of leaflet initiation, Chelidonium majus subsp. asiaticum (basipetal) and Eschscholzia californica (acropetal). Because E. californica has been studied in some detail, we focused on C. majus and asked how basipetal pattern is achieved. •
Since only immature leaf primordial tissue has leaflet-generating competency, we performed histological and gene expression analyses on markers of the tissue maturation state. In addition, we performed a time-course analysis of leaf primordial growth. •
Quantitative reverse transcription-PCR analysis demonstrated that a putative regulator of tissue maturation in C. majus, the CINCINNATA homolog, had higher expression in apical parts than in basal parts during the organogenetic phase. In contrast, expression of the CIN homolog was not elevated in either the apical or basal parts in E. californica during the organogenetic phase. •
In C. majus, apical parts of leaf primordia have already lost leaflet-generating competency during the organogenetic phase. We propose that precocious progression of the maturation process instructs basipetal progression of leaflet initiation in C. majus. This is not the mirror image of data on E. californica, which shows the opposite direction in leaflet formation, indicating that variation in direction is not attributable to a change in a single factor.
在复叶上，小叶原基沿着顶端-基部轴重复形成，方向在分类群之间变化。为什么和如何在物种之间变化尚待解决，尽管有人提出单个因素的变化会导致这种变化。在这项研究中，我们比较了罂粟科中两种具有不同小叶起始方向的物种，即Chelidonium majus subsp. asiaticum（向基）和 Eschscholzia californica（向顶）。由于 E. californica 已经被研究得相当详细，我们专注于 C. majus，并探讨了向基模式是如何实现的。
由于只有未成熟的叶原基组织具有产生小叶的能力，我们对组织成熟状态的标记进行了组织学和基因表达分析。此外，我们还对叶原基生长进行了时间进程分析。
定量逆转录-PCR 分析表明，C. majus 中组织成熟的假定调节因子 CINCINNATA 同源物在器官发生阶段的顶端部分比基部部分的表达更高。相比之下，在器官发生阶段，E. californica 中 CIN 同源物在顶端或基部部分的表达都没有升高。
在 C. majus 中，叶原基的顶端部分在器官发生阶段已经失去了产生小叶的能力。我们提出，成熟过程的提前进展指示了 C. majus 中小叶起始的向基进展。这与 E. californica 的数据并不相同，后者显示出小叶形成的相反方向，表明方向的变化不是归因于单个因素的变化。
