1-aminocyclopropane-1-carboxylic acid (ACC), a precursor for ethylene, stimulates the switch from a vegetative to a sexual reproductive phase in the marine red alga Pyropia species. This study explored the effects of ethylene biosynthesis inhibitors on the sexual reproduction of gametophytes of the red alga Pyropia yezoensis to gain a functional understanding of the role of ACC as a plant hormone in red algae. Here we show that two inhibitors of ACC synthesis in higher plants, 2-aminoethoxyvinyl glycine (AVG) and aminooxyacetic acid (AOA), had no effect on the growth and gametogenesis of P. yezoensis. In contrast, exogenous application of α-aminoisobutyric acid (AIB), a structural analog of ACC that blocks the conversion of ACC to ethylene in higher plants, induced the formation of spermatangia and carpospores in a similar manner as ACC, without endogenous ACC accumulation. The treatment of AIB failed to inhibit ethylene production in the gametophytes. The present results suggest that AIB mimics the effect of ACC to induce the sexual reproduction and support our previous study that ACC has a role in the regulation of the sexual reproduction independent from ethylene.

1-氨基环丙烷-1-羧酸（ACC）是乙烯的前体，可刺激海洋红藻拟南芥从营养繁殖期向有性繁殖期转变。这项研究探索了乙烯生物合成抑制剂对红藻Pyropia yezoensis配子体有性繁殖的影响，以了解ACC在红藻中作为植物激素的功能。在这里，我们显示了在高等植物中的两种ACC合成抑制剂，2-氨基乙氧基乙烯基甘氨酸（AVG）和氨基氧基乙酸（AOA），对yezoensis的生长和配子体没有影响。相反，外源应用α-氨基异丁酸（AIB），即ACC的结构类似物，阻止高等植物中ACC向乙烯的转化，以与ACC类似的方式诱导了精子和孢子的形成，而没有内源性ACC积累。AIB的处理不能抑制配子体中乙烯的产生。目前的结果表明，AIB模仿ACC诱导有性生殖的作用，并支持我们先前的研究，即ACC在独立于乙烯的性生殖调节中具有作用。