Uji Toshiki, Endo Harune, Mizuta Hiroyuki
Laboratory of Aquaculture Genetics and Genomics, Division of Marine Life Science, Faculty of Fisheries Sciences, Hokkaido University, Hakodate, Japan.
Front Plant Sci. 2020 Feb 12;11:60. doi: 10.3389/fpls.2020.00060. eCollection 2020.
The transition from the vegetative to sexually reproductive phase is the most dynamic change to occur during a plant's life cycle. In the present study, we showed that the ethylene precursor 1-aminocylopropane-1-carboxylic acid (ACC) induces sexual reproduction in the marine red alga independently from ethylene. Exogenous application of ACC, which contains a three membered carbocyclic ring, promoted the formation of spermatia and carporspores in gametophytes, whereas ethephon, an ethylene-releasing compound, did not stimulate sexual reproduction. In addition, an ACC analog, 1-aminocyclobutane-1-carboxylic acid (ACBC), which contains a four membered carbocyclic ring, promoted sexual reproduction and enhanced tolerance to oxidative stress in the same manner as ACC, but 1-aminocyclopentane-1-carboxylic acid (cycloleucine; which contains a cyclopentane ring) did not. The application of ACC increased the generation of reactive oxygen species (ROS) and induced the expression of gene encoding NADPH oxidase. ACC also stimulated the synthesis of ascorbate (AsA) by inducing transcripts of , which encodes galactono-1,4-lactone dehydrogenase, the catalyst for the final enzymatic step of the AsA biosynthetic pathway. Conversely, ACC caused a decrease in the synthesis of glutathione (GSH) by repressing transcripts of , which encodes glutamate cysteine ligase, the catalyst for the rate-limiting step in the formation of GSH. These results suggest a possible role played by ACC as a signaling molecule independent from ethylene in the regulation of sexual reproduction through alterations to the redox state in .
从营养生长阶段到有性生殖阶段的转变是植物生命周期中发生的最动态的变化。在本研究中，我们表明乙烯前体1-氨基环丙烷-1-羧酸（ACC）可独立于乙烯诱导海洋红藻进行有性生殖。含有三元碳环的ACC外源施用促进了配子体中精子和果孢子的形成，而乙烯释放化合物乙烯利则不刺激有性生殖。此外，含有四元碳环的ACC类似物1-氨基环丁烷-1-羧酸（ACBC）以与ACC相同的方式促进有性生殖并增强对氧化应激的耐受性，但1-氨基环戊烷-1-羧酸（环亮氨酸；含有环戊烷环）则没有。ACC的施用增加了活性氧（ROS）的产生并诱导了编码NADPH氧化酶的基因的表达。ACC还通过诱导编码半乳糖内酯脱氢酶（AsA生物合成途径最后一步酶促反应的催化剂）的转录本来刺激抗坏血酸（AsA）的合成。相反，ACC通过抑制编码谷氨酸半胱氨酸连接酶（GSH形成限速步骤的催化剂）的转录本来导致谷胱甘肽（GSH）合成减少。这些结果表明ACC作为一种独立于乙烯的信号分子，可能通过改变氧化还原状态在有性生殖调控中发挥作用。
