Helminthosporol, a natural growth regulator isolated from a fungus, stimulates hypocotyl growth and seed germination, similar to gibberellin (GA). We recently reported that helminthosporic acid (H-acid), a synthetic analog of helminthosporol, acts as an agonist of GA receptor. In this study, we showed that a H-acid analog, in which the hydroxymethyl group at the C-8 position of H-acid was converted to a keto group, acts as a selective GA receptor agonist. 1) This analog shows higher hypocotyl elongation activity in Arabidopsis than H-acid does, and induces the degradation of DELLA protein and 2) leads to the formation of the GID1-DELLA complex and 3) regulates the expression of GA-related genes. In addition, 4) its hypocotyl elongation activity was not observed in a atgid1a single mutant, and 5) this analog could promote only the interaction between specific GA receptors and DELLA proteins in vitro. Taken together, our results strongly suggest that the selectivity of the reported H-acid analog depends on the specificity of its GA receptor binding activity.

Helminthosporol是一种从真菌中分离出来的天然生长调节剂，与赤霉素（GA）相似，可刺激下胚轴生长和种子发芽。我们最近报道了蠕虫孢子酸（H-酸），一种蠕虫孢子酚的合成类似物，起着GA受体激动剂的作用。在这项研究中，我们发现，一个H-酸类似物，其中在H-酸的C-8位置上的羟甲基转化为酮基，作为一种选择性GA受体激动剂。1）该类似物在拟南芥中显示出比H-酸更高的下胚轴伸长活性，并诱导DELLA蛋白降解； 2）导致GID1-DELLA复合物形成； 3）调节GA相关基因的表达。此外，4）在atgid1a中未观察到其下胚轴伸长活性5）该类似物只能在体外促进特定GA受体与DELLA蛋白之间的相互作用。两者合计，我们的结果强烈表明，所报道的H-酸类似物的选择性取决于其GA受体结合活性的特异性。