Identification of Auxin Activity Like 1, a chemical with weak functions in auxin signaling pathway
A new synthetic auxin AAL1 with new structure was identified. Different from known auxins, it has weak effects. By AAL1, we found specific amino acids could restore the effects of auxin with similar structure.
Auxin, one of the most important phytohormones, plays crucial roles in plant growth, development and environmental response. Although many critical regulators have been identified in auxin signaling pathway, some factors, especially those with weak fine-tuning roles, are still yet to be discovered. Through chemical genetic screenings, we identified a small molecule, Auxin Activity Like 1 (AAL1), which can effectively inhibit dark-grown Arabidopsis thaliana seedlings. Genetic screening identified AAL1 resistant mutants are also hyposensitive to indole-3-acetic acid (IAA) and 2,4-dichlorophenoxyacetic acid (2,4-D). AAL1 resistant mutants such as shy2-3c and ecr1-2 are well characterized as mutants in auxin signaling pathway. Genetic studies showed that AAL1 functions through auxin receptor Transport Inhibitor Response1 (TIR1) and its functions depend on auxin influx and efflux carriers. Compared with known auxins, AAL1 exhibits relatively weak effects on plant growth, with 20 µM and 50 µM IC50 (half growth inhibition chemical concentration) in root and hypocotyl growth respectively. Interestingly, we found the inhibitory effects of AAL1 and IAA could be partially restored by tyrosine and tryptophan respectively, suggesting some amino acids can also affect auxin signaling pathway in a moderate manner. Taken together, our results demonstrate that AAL1 acts through auxin signaling pathway, and AAL1, as a weak auxin activity analog, provides us a tool to study weak genetic interactions in auxin pathway.
KeywordsArabidopsis Chemical genetics AAL1 Auxin Amino acid
We thank Dr. Xiaoya Chen (SIPPE) and Dr. Yongfei Wang for providing the Col-0 EMS mutant M2 seeds. We also thank Dr. Zuhua He (SIPPE), Hai Huang (SIPPE) and Lin Xu (SIPPE) for providing auxin-associated mutants. This work was supported by grants from the National Natural Science Foundation of China (31171293 and 31371361) and the One Hundred Talents grant of the Chinese Academy of Sciences to Yang Zhao, and the National Natural Science Foundation of China (31630014) and the Strategic Priority Program of Chinese Academy of Sciences (XDB27020104) to Laigeng Li.
YZ and WBL planned and designed the research. WBL and HML performed experiments, conducted fieldwork, analyzed data and wrote the manuscript. LTL helped to perform experiments. YZ, LGL and YJZ modified the manuscript. PX, DQL, YJY and ZX helped to modify the manuscript. YJZ and LGL provided platform for some experiments.
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflict of interest.
- Narukawa-Nara M, Nakamura A, Kikuzato K, Kakei Y, Sato A, Mitani Y, Yamasaki-Kokudo Y, Ishii T, Hayashi K, Asami T, Ogura T, Yoshida S, Fujioka S, Kamakura T, Kawatsu T, Tachikawa M, Soeno K, Shimada Y (2016) Aminooxy-naphthylpropionic acid and its derivatives are inhibitors of auxin biosynthesis targeting l-tryptophan aminotransferase: structure-activity relationships. Plant J 87(3):245–257CrossRefGoogle Scholar
- Okushima Y, Overvoorde PJ, Arima K, Alonso JM, Chan A, Chang C, Ecker JR, Hughes B, Lui A, Nguyen D, Onodera C, Quach H, Smith A, Yu G, Theologis A (2005) Functional genomic analysis of the AUXIN RESPONSE FACTOR gene family members in Arabidopsis thaliana: unique and overlapping functions of ARF7 and ARF19. Plant cell 17(2):444–463CrossRefGoogle Scholar
- Park SY, Fung P, Nishimura N, Jensen DR, Fujii H, Zhao Y, Lumba S, Santiago J, Rodrigues A, Chow TF, Alfred SE, Bonetta D, Finkelstein R, Provart NJ, Desveaux D, Rodriguez PL, McCourt P, Zhu JK, Schroeder JI, Volkman BF, Cutler SR (2009) Abscisic acid inhibits type 2C protein phosphatases via the PYR/PYL family of START proteins. Science 324(5930):1068–1071PubMedPubMedCentralGoogle Scholar
- Swarup K, Benková E, Swarup R, Casimiro I, Péret B, Yang Y, Parry G, Nielsen E, De Smet I, Vanneste S, Levesque MP, Carrier D, James N, Calvo V, Ljung K, Kramer E, Roberts R, Graham N, Marillonnet S, Patel K, Jones JD, Taylor CG, Schachtman DP, May S, Sandberg G, Benfey P, Friml J, Kerr I, Beeckman T, Laplaze L, Bennett MJ (2008) The auxin influx carrier LAX3 promotes lateral root emergence. Nat Cell Biol 10(8):946–954CrossRefGoogle Scholar
- Walsh TA, Neal R, Merlo AO, Honma M, Hicks GR, Wolff K, Matsumura W, Davies JP (2006) Mutations in an auxin receptor homolog AFB5 and in SGT1b confer resistance to synthetic picolinate auxins and not to 2,4-dichlorophenoxyacetic acid or indole-3-acetic acid in Arabidopsis. Plant Physiol 142(2):542–545CrossRefGoogle Scholar