A molecular basis behind heterophylly in an amphibious plant, Ranunculus trichophyllus.
A molecular basis behind heterophylly in an amphibious plant, Ranunculus trichophyllus.
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DOI：
10.1371/journal.pgen.1007208
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发表时间：
2018-03
期刊：
影响因子：
4.5
通讯作者：
Lee I
中科院分区：
文献类型：
--
作者：
Kim J;Joo Y;Kyung J;Jeon M;Park JY;Lee HG;Chung DS;Lee E;Lee I
毛茛是一种两栖植物，如果生长在水下，会产生薄而圆柱形的叶子，但如果生长在陆地上，会产生厚而宽的叶子。我们发现，这种异叶性是广泛控制的两种植物激素，脱落酸（阿坝）和乙烯，控制陆地和水生叶发育。水生叶产生较高水平的乙烯，但较低水平的阿坝比陆地叶。在水生叶中，其独特的性状，狭窄的形状，气孔的缺乏，和减少导管的发展是由EIN 3介导的过度激活的远轴基因，RtKANADI，并伴随着减少气孔和血管相关的NAC-DOMAIN 7（VDN 7）。与此相反，在陆生叶，ABI 3介导的激活的近轴基因，RtHD-ZIPIII，和STOMAGEN和VDN 7建立叶极性，气孔和导管的发展。寒冷、低氧等外界刺激也能诱导毛叶杜鹃的异叶性，并伴随着与水生反应相似的叶极性基因表达的变化。一种近缘陆生植物R.石龙鱼没有表现出这种异叶性反应，这表明阿坝/乙烯信号和叶极性的变化是水生适应的关键进化步骤之一。水生环境的进化适应广泛存在于陆生植物的不同分支中。为了了解这种适应背后的分子基础，我们分析了毛茛，两栖植物产生不同的叶子形状取决于生长条件。这种植物的水生叶产生更高水平的乙烯，这导致由EIN 3（乙烯信号转导子）和抑制调节气孔和木质部发育的基因的远轴基因组成的遗传电路过度激活。相反，陆生叶产生较高水平的阿坝，其激活近轴基因并引起气孔和木质部发育的激活。在近缘陆生植物R中没有观察到这种淹水后阿坝/乙烯信号和叶极性的变化。这表明它们是水生适应的关键进化步骤。
Ranunculus trichophyllus is an amphibious plant that produces thin and cylindrical leaves if grown under water but thick and broad leaves if grown on land. We found that such heterophylly is widely controlled by two plant hormones, abscisic acid (ABA) and ethylene, which control terrestrial and aquatic leaf development respectively. Aquatic leaves produced higher levels of ethylene but lower levels of ABA than terrestrial leaves. In aquatic leaves, their distinct traits with narrow shape, lack of stomata, and reduced vessel development were caused by EIN3-mediated overactivation of abaxial genes, RtKANADIs, and accompanying with reductions of STOMAGEN and VASCULAR-RELATED NAC-DOMAIN7 (VDN7). In contrast, in terrestrial leaves, ABI3-mediated activation of the adaxial genes, RtHD-ZIPIIIs, and STOMAGEN and VDN7 established leaf polarity, and stomata and vessel developments. Heterophylly of R.trichophyllus could be also induced by external cues such as cold and hypoxia, which is accompanied with the changes in the expression of leaf polarity genes similar to aquatic response. A closely-related land plant R. sceleratus did not show such heterophyllic responses, suggesting that the changes in the ABA/ethylene signaling and leaf polarity are one of key evolutionary steps for aquatic adaptation. Evolutionary adaptation into aquatic environment is widely observed in diverse clades of land plants. To understand the molecular basis behind such adaptation, we analyzed Ranunculus trichophyllus, an amphibious plant producing different leaf shape depending on the growth conditions. Aquatic leaves of this plant produce higher levels of ethylene, which causes overactivation of genetic circuits composed of EIN3, an ethylene signaling transducer, and abaxial genes that suppress genes regulating stomata and xylem development. In contrast, terrestrial leaves produce higher levels of ABA, which activates adaxial genes and causes activation of stomata and xylem developments. Such changes in the ABA/ethylene signaling and leaf polarity after submergence were not observed in the closely-related land plant R. sceleratus, indicating that they are key evolutionary steps towards aquatic adaptation.
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