Auxin is the first discovered plant hormone and is essential for many aspects of plant growth and development. Indole-3-acetic acid (IAA) is the main auxin and plays pivotal roles in intercellular communication through polar auxin transport. Phenylacetic acid (PAA) is another natural auxin that does not show polar movement. Although a wide range of species have been shown to produce PAA, its biosynthesis, inactivation and physiological significance in plants are largely unknown. In this study, we demonstrate that overexpression of the CYP79A2 gene, which is involved in benzylglucosinolate synthesis, remarkably increased the levels of PAA and enhanced lateral root formation in Arabidopsis. This coincided with a significant reduction in the levels of IAA. The results from auxin metabolite quantification suggest that the PAA-dependent induction of GRETCHEN HAGEN 3 (GH3) genes, which encode auxin-amido synthetases, promote the inactivation of IAA. Similarly, an increase in IAA synthesis, via the indole-3-acetaldoxime pathway, significantly reduced the levels of PAA. The same adjustment of IAA and PAA levels was also observed by applying each auxin to wild-type plants. These results show that GH3 auxin-amido synthetases can alter the ratio of IAA and PAA in plant growth and development.

中文翻译：

---

GH3生长素-酰胺基合成酶改变拟南芥中吲哚-3-乙酸和苯乙酸的比率

生长素是最早发现的植物激素，对于植物生长和发育的许多方面都是必不可少的。吲哚-3-乙酸（IAA）是主要的植物生长素，在通过极性植物生长素转运的细胞间通讯中起关键作用。苯乙酸（PAA）是另一种天然植物生长素，不显示极性移动。尽管已显示出广泛的物种可产生PAA，但其在植物中的生物合成，失活和生理意义仍然未知。在这项研究中，我们证明了CYP79A2基因的过表达（参与芥子油基苄基合成）显着增加了拟南芥中PAA的水平并增强了侧根的形成。这恰好与IAA水平的显着降低相吻合。生长素代谢物定量的结果表明，编码植物生长素-酰胺基合成酶的GRETCHEN HAGEN 3（GH3）基因的PAA依赖性诱导促进了IAA的失活。同样，通过吲哚-3-乙醛肟途径，IAA合成的增加也显着降低了PAA的水平。通过将每种生长素应用于野生型植物，也观察到了对IAA和PAA水平的相同调节。这些结果表明，GH3生长素-酰胺基合成酶可以改变植物生长发育中IAA和PAA的比例。通过将每种生长素应用于野生型植物，也观察到了对IAA和PAA水平的相同调节。这些结果表明，GH3生长素-酰胺基合成酶可以改变植物生长发育中IAA和PAA的比例。通过将每种生长素应用于野生型植物，也观察到了对IAA和PAA水平的相同调节。这些结果表明，GH3生长素-酰胺基合成酶可以改变植物生长发育中IAA和PAA的比例。