Ethylene-independent functions of the ethylene precursor ACC in Marchantia polymorpha
Ethylene-independent functions of the ethylene precursor ACC in Marchantia polymorpha
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DOI：
10.1038/s41477-020-00784-y
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发表时间：
2020-10-26
期刊：
影响因子：
18
通讯作者：
Chang, Caren
中科院分区：
文献类型：
--
作者：
Li, Dongdong;Flores-Sandoval, Eduardo;Chang, Caren
地钱缺乏高等植物中将ACC转化为乙烯的酶。乙烯突变体的遗传特征和外源分子的处理表明，在该物种中，ACC和乙烯具有独立的功能。植物激素乙烯在生长和发育中具有许多作用（1）。在种子植物中，乙烯前体1-氨基环丙烷-1-羧酸（ACC）通过ACC氧化酶（ACO）转化为乙烯，用ACC处理会诱导乙烯反应（2）。然而，非种子植物缺乏ACO同系物（3-8），这使我们研究ACC和乙烯之间的关系，地钱多形。在这里，我们表明，ACC和乙烯可以诱导地钱不同的生长反应。乙烯增加植物和芽的大小，诱导更多的芽杯和促进芽休眠。正如预测的那样，Mpctr 1敲除突变体显示组成型乙烯反应，而Mpein 3敲除突变体表现出乙烯不敏感性。与野生型相比，Mpctr 1芽具有更多和更大的表皮细胞，而Mpein 3芽具有更少和更小的表皮细胞，这表明乙烯促进细胞分裂和生长发育的芽。相比之下，ACC处理通过抑制细胞分裂来抑制芽孢生长和发育，即使在Mpein 3敲除等位基因中也是如此。一个或两个ACC合成酶（ACS）基因同源物的敲除突变体产生可忽略不计的ACC水平，有更多和更大的芽杯，并有更多的扩展叶状体分支。Mpacs 2和Mpacs 1 Mpacs 2芽也显示出高频率的异常顶端缺口（分生组织），这在乙烯突变体中没有观察到。这些结果表明，乙烯和ACC有不同的功能，并建议ACC是地钱的信号分子。ACC可能是一个进化上保守的信号，早于其在高等植物中有效转化为乙烯。
Marchantia polymorpha lacks the enzyme that converts ACC into ethylene in higher plants. Genetic characterization of ethylene mutants and treatments with exogenous molecules suggest that, in this species, ACC and ethylene have independent functions.The plant hormone ethylene has many roles in growth and development(1). In seed plants, the ethylene precursor 1-aminocyclopropane-1-carboxylic acid (ACC) is converted into ethylene by ACC oxidase (ACO), and treatment with ACC induces ethylene responses(2). However, non-seed plants lack ACO homologues(3-8), which led us to examine the relationship between ACC and ethylene in the liverwort Marchantia polymorpha. Here, we demonstrate that ACC and ethylene can induce divergent growth responses in Marchantia. Ethylene increases plant and gemma size, induces more gemma cups and promotes gemmae dormancy. As predicted, Mpctr1-knockout mutants display constitutive ethylene responses, whereas Mpein3-knockout mutants exhibit ethylene insensitivity. Compared with the wild type, Mpctr1 gemmae have more and larger epidermal cells, whereas Mpein3 gemmae have fewer and smaller epidermal cells, suggesting that ethylene promotes cell division and growth in developing gemmae. By contrast, ACC treatment inhibits gemma growth and development by suppressing cell division, even in the Mpein3-knockout alleles. Knockout mutants of one or both ACC SYNTHASE (ACS) gene homologues produce negligible levels of ACC, have more and larger gemma cups, and have more-expanded thallus branches. Mpacs2 and Mpacs1 Mpacs2 gemmae also display a high frequency of abnormal apical notches (meristems) that are not observed in ethylene mutants. These findings reveal that ethylene and ACC have distinct functions, and suggest that ACC is a signalling molecule in Marchantia. ACC may be an evolutionarily conserved signal that predates its efficient conversion to ethylene in higher plants.