Peking-Yale Joint Center for Plant Molecular Genetics and Agro-biotechnology, National Key Laboratory of Protein and Plant Gene Research, and Peking-Tsinghua Center for Life Sciences, College of Life Sciences, Peking University, Beijing 100871, China.
Proc Natl Acad Sci U S A. 2014 Mar 18;111(11):3913-20. doi: 10.1073/pnas.1402491111. Epub 2014 Mar 5.
The early life of terrestrial seed plants often starts under the soil in subterranean darkness. Over time and through adaptation, plants have evolved an elaborate etiolation process that enables seedlings to emerge from soil and acquire autotrophic ability. This process, however, requires seedlings to be able to sense the soil condition and relay this information accordingly to modulate both the seedlings' growth and the formation of photosynthetic apparatus. The mechanism by which soil overlay drives morphogenetic changes in plants, however, remains poorly understood, particularly with regard to the means by which the cellular processes of different organs are coordinated in response to disparate soil conditions. Here, we illustrate that the soil overlay quantitatively activates seedlings' ethylene production, and an EIN3/EIN3-like 1-dependent ethylene-response cascade is required for seedlings to successfully emerge from the soil. Under soil, an ERF1 pathway is activated in the hypocotyl to slow down cell elongation, whereas a PIF3 pathway is activated in the cotyledon to control the preassembly of photosynthetic machinery. Moreover, this latter PIF3 pathway appears to be coupled to the ERF1-regulated upward-growth rate. The coupling of these two pathways facilitates the synchronized progression of etioplast maturation and hypocotyl growth, which, in turn, ultimately enables seedlings to maintain the amount of protochlorophyllide required for rapid acquisition of photoautotrophic capacity without suffering from photooxidative damage during the dark-to-light transition. Our findings illustrate the existence of a genetic signaling pathway driving soil-induced plant morphogenesis and define the specific role of ethylene in orchestrating organ-specific soil responses in Arabidopsis seedlings.
陆生种子植物的早期生活通常在地下的黑暗中开始。随着时间的推移和适应，植物已经进化出了一种精细的黄化过程，使幼苗能够从土壤中冒出来并获得自养能力。然而，这个过程要求幼苗能够感知土壤条件，并相应地传递信息，以调节幼苗的生长和光合器官的形成。然而，土壤覆盖如何驱动植物形态发生变化的机制仍知之甚少，特别是在不同器官的细胞过程如何协调以应对不同的土壤条件方面。在这里，我们表明，土壤覆盖定量地激活了幼苗的乙烯产生，并且 EIN3/EIN3-like 1 依赖的乙烯反应级联对于幼苗成功地从土壤中冒出来是必需的。在土壤中，ERF1 途径在胚轴中被激活以减缓细胞伸长，而 PIF3 途径在子叶中被激活以控制光合机器的预组装。此外，后一种 PIF3 途径似乎与 ERF1 调节的向上生长速度相关联。这两个途径的耦合促进了质体成熟和胚轴生长的同步进展，这反过来又使幼苗能够在黑暗到光照的过渡期间保持快速获得光自养能力所需的原叶绿素含量，而不会遭受光氧化损伤。我们的发现说明了一个遗传信号通路的存在，该通路驱动着土壤诱导的植物形态发生，并定义了乙烯在协调拟南芥幼苗中器官特异性土壤反应中的特定作用。
