Local conjugation of auxin by the GH3 amido synthetases is required for normal development of roots and flowers in Arabidopsis

Chemical genetic screening identifies nalacin as an inhibitor of GH3 amido synthetase for auxin conjugation

“…Nalacin can directly bind to several group II GH3s (Figure 4A–C) and inhibit GH3-mediated conjugation of Glu or Asp to IAA (Figure 4D–F), leading to an increase in endogenous IAA levels in planta (Figure 3C). In support of that, nalacin-treated Col-0 mimicked the phenotypes of gh3 octuple mutant (Figure 3G–I), which could not be observed in gh3.1,2,3,4,6 (11) due to the redundant roles of GH3.17 (37). In addition, gh3 octuple mutant showed resistance to nalacin treatment in both phenotypic changes and perturbation of endogenous IAA levels (Figure 3L).…”

“…As stated above, nineteen GH3 genes can be divided into three phylogenetic groups (Figure S3A) (15, 16), among which the group II GH3 is responsible for amino acid conjugation of IAA. A recent report showed that a mutant with loss of function of all eight group II GH3 ( △8gh3 ) displayed a short primary root and an elevated number of adventitious roots (37), a pattern reminiscent of the effects of nalacin (Figure 1C). We found that △8gh3 was resistant to nalacin treatment, while still being responsive to exogenous IAA treatment (Figure 3G–I).…”

“…To overcome the genetic redundancy of GH3 s, Guo et al . utilized the CRISPR/Cas9 gene editing method to generate gh3 mutants with loss of function of multiple group II GH3s in Arabidopsis and confirmed their redundant functions in regulating root growth and a critical role of GH3.9 in fertility (37). gh3oct mutant was also reported to have enhanced tolerance to salinity and water deficit (49).…”

“…Subsequent studies have shown that the GH3s are spatiotemporally induced by many other plant hormones and ambient signals (such as biotic and abiotic stresses), and widely distribute in dicots and monocots (48), indicating their involvement in the plant development and environmental accommodation. Substantial genome analyses in various plants reveal great numbers of GH3 genes and their high degree of redundancy that have been well illustrated by a series of studies in Arabidopsis (11, 15, 37). To overcome the genetic redundancy of GH3 s, Guo et al .…”

“…genes and their high degree of redundancy that have been well illustrated by a series of studies in Arabidopsis (11,15,37). To overcome the genetic redundancy of GH3s, Guo et al utilized the CRISPR/Cas9 gene editing method to generate gh3 mutants with loss of function of multiple group II GH3s…”