Gu Shin-Yuan, Wang Long-Chi, Cheuh Chiao-Mei, Lo Wan-Sheng
Institute of Plant and Microbial Biology, Academia Sinica, Taipei, Taiwan.
Department of Life Sciences, National Central University, Taoyuan City, Taiwan.
Front Plant Sci. 2019 May 14;10:600. doi: 10.3389/fpls.2019.00600. eCollection 2019.
The plant hormone ethylene plays a regulatory role in development in light- and dark-grown seedlings. We previously isolated a group of small-molecule compounds with a quinazolinone backbone, which were named acsinones (for ACC synthase inhibitor quinazolinones), that act as uncompetitive inhibitors of 1-aminocyclopropane-1-carboxylic acid (ACC) synthase (ACS). Thus, the triple response phenotype, which consists of shortened hypocotyls and roots, radial swelling of hypocotyls and exaggerated curvature of apical hooks, was suppressed by acsinones in dark-grown (etiolated) () seedlings. Here, we describe our isolation and characterization of an Arabidopsis () mutant, which showed reduced sensitivity to acsinones in etiolated seedlings. Map-based cloning of revealed an amino acid substitution in (), which is required for cell wall biogenesis and stress resistance in Arabidopsis. Etiolated seedlings of showed short hypocotyls and roots, which were augmented in combination with . Consistently, seedlings showed enhanced sensitivity to exogenous ACC to suppress primary root elongation as compared with the wild type. After introducing to mutants completely insensitive to ethylene, genetic analysis indicated that an intact ethylene response pathway is essential for the alterations in root and apical hook but not hypocotyl in etiolated seedlings. Furthermore, a mild yet significantly increased ethylene level in mutants was related to elevated mRNA level and activity of ACC oxidase (ACO). Moreover, genes associated with ethylene biosynthesis ( and ) and response ( and ) were upregulated in etiolated seedlings. By characterizing a new recessive allele of , we reveal that CTL1 negatively regulates ACO activity and the ethylene response, which thus contributes to understanding a role for ethylene in root elongation in response to perturbed cell wall integrity.
植物激素乙烯在光照和黑暗条件下生长的幼苗发育过程中发挥着调节作用。我们之前分离出了一组具有喹唑啉酮骨架的小分子化合物，将其命名为吖辛酮（用于1-氨基环丙烷-1-羧酸（ACC）合酶抑制剂喹唑啉酮），它们作为ACC合酶（ACS）的非竞争性抑制剂发挥作用。因此，在黑暗中生长（黄化）的幼苗中，由下胚轴和根缩短、下胚轴径向肿胀以及顶端弯钩过度弯曲组成的三重反应表型被吖辛酮抑制。在此，我们描述了拟南芥突变体的分离和表征，该突变体在黄化幼苗中对吖辛酮的敏感性降低。基于图谱的克隆显示，突变体中一个与细胞壁生物合成和拟南芥抗逆性相关的基因（）发生了氨基酸替换。突变体的黄化幼苗表现出短的下胚轴和根，与该基因共同作用时这些特征会增强。同样，与野生型相比，突变体幼苗对外源ACC抑制主根伸长表现出更高的敏感性。将该基因导入对乙烯完全不敏感的突变体后，遗传分析表明完整的乙烯反应途径对于黄化幼苗根和顶端弯钩而非下胚轴的变化至关重要。此外，突变体中乙烯水平虽轻微但显著升高，这与ACC氧化酶（ACO）的mRNA水平和活性升高有关。而且，与乙烯生物合成（和）及反应（和）相关的基因在黄化突变体幼苗中上调。通过对该基因一个新的隐性等位基因进行表征，我们揭示CTL1负向调节ACO活性和乙烯反应，这有助于理解乙烯在响应细胞壁完整性扰动时对根伸长的作用。
