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Salicylic acid regulates adventitious root formation via competitive inhibition of the auxin conjugation enzyme CsGH3.5 in cucumber hypocotyls.
Planta. 2020 Oct 07; 252(5):75.P

Abstract

MAIN CONCLUSION

Exogenous SA treatment at appropriate concentrations promotes adventitious root formation in cucumber hypocotyls, via competitive inhibiting the IAA-Asp synthetase activity of CsGH3.5, and increasing the local free IAA level. Adventitious root formation is critical for the cutting propagation of horticultural plants. Indole-3-acetic acid (IAA) has been shown to play a central role in regulating this process, while for salicylic acid (SA), its exact effects and regulatory mechanism have not been elucidated. In this study, we showed that exogenous SA treatment at the concentrations of both 50 and 100 µM promoted adventitious root formation at the base of the hypocotyl of cucumber seedlings. At these concentrations, SA could induce the expression of CYCLIN and Cyclin-dependent Kinase (CDK) genes during adventitious rooting. IAA was shown to be involved in SA-induced adventitious root formation in cucumber hypocotyls. Exposure to exogenous SA led to a slight increase in the free IAA content, and pre-treatment with the auxin transport inhibitor 1-naphthylphthalamic acid (NPA) almost completely abolished the inducible effects of SA on adventitious root number. SA-induced IAA accumulation was also associated with the enhanced expression of Gretchen Hagen3.5 (CsGH3.5). The in vitro enzymatic assay indicated that CsGH3.5 has both IAA- and SA-amido synthetase activity and prefers aspartate (Asp) as the amino acid conjugate. The Asp concentration dictated the functional activity of CsGH3.5 on IAA. Both affinity and catalytic efficiency (Kcat/Km) increased when the Asp concentration increased from 0.3 to 1 mM. In contrast, CsGH3.5 showed equal catalytic efficiency for SA at low and high Asp concentrations. Furthermore, SA functioned as a competitive inhibitor of the IAA-Asp synthetase activity of CsGH3.5. During adventitious formation, SA application indeed repressed the IAA-Asp levels in the rooting zone. These data show that SA plays an inducible role in adventitious root formation in cucumber through competitive inhibition of the auxin conjugation enzyme CsGH3.5. SA reduces the IAA conjugate levels, thereby increasing the local free IAA level and ultimately enhancing adventitious root formation.

Authors+Show Affiliations

Ministry of Agriculture, Key Laboratory of Horticultural Crop Biology and Germplasm Innovation, Institute of Vegetables and Flowers, Chinese Academy of Agricultural Sciences, Beijing, People's Republic of China. dongchunjuan@caas.cn.Ministry of Agriculture, Key Laboratory of Horticultural Crop Biology and Germplasm Innovation, Institute of Vegetables and Flowers, Chinese Academy of Agricultural Sciences, Beijing, People's Republic of China.Ministry of Agriculture, Key Laboratory of Horticultural Crop Biology and Germplasm Innovation, Institute of Vegetables and Flowers, Chinese Academy of Agricultural Sciences, Beijing, People's Republic of China.Ministry of Agriculture, Key Laboratory of Horticultural Crop Biology and Germplasm Innovation, Institute of Vegetables and Flowers, Chinese Academy of Agricultural Sciences, Beijing, People's Republic of China.Ministry of Agriculture, Key Laboratory of Horticultural Crop Biology and Germplasm Innovation, Institute of Vegetables and Flowers, Chinese Academy of Agricultural Sciences, Beijing, People's Republic of China. shangqingmao@caas.cn.

Pub Type(s)

Journal Article

Language

eng

PubMed ID

33026530

Citation

Dong, Chun-Juan, et al. "Salicylic Acid Regulates Adventitious Root Formation Via Competitive Inhibition of the Auxin Conjugation Enzyme CsGH3.5 in Cucumber Hypocotyls." Planta, vol. 252, no. 5, 2020, p. 75.
Dong CJ, Liu XY, Xie LL, et al. Salicylic acid regulates adventitious root formation via competitive inhibition of the auxin conjugation enzyme CsGH3.5 in cucumber hypocotyls. Planta. 2020;252(5):75.
Dong, C. J., Liu, X. Y., Xie, L. L., Wang, L. L., & Shang, Q. M. (2020). Salicylic acid regulates adventitious root formation via competitive inhibition of the auxin conjugation enzyme CsGH3.5 in cucumber hypocotyls. Planta, 252(5), 75. https://doi.org/10.1007/s00425-020-03467-2
Dong CJ, et al. Salicylic Acid Regulates Adventitious Root Formation Via Competitive Inhibition of the Auxin Conjugation Enzyme CsGH3.5 in Cucumber Hypocotyls. Planta. 2020 Oct 7;252(5):75. PubMed PMID: 33026530.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Salicylic acid regulates adventitious root formation via competitive inhibition of the auxin conjugation enzyme CsGH3.5 in cucumber hypocotyls. AU - Dong,Chun-Juan, AU - Liu,Xin-Yan, AU - Xie,Lu-Lu, AU - Wang,Ling-Ling, AU - Shang,Qing-Mao, Y1 - 2020/10/07/ PY - 2020/06/01/received PY - 2020/09/12/accepted PY - 2020/10/7/entrez PY - 2020/10/8/pubmed PY - 2021/3/10/medline KW - Acyl-amido synthetase KW - Adventitious root KW - Cucumber (cucumis sativus) KW - Gretchen Hagen3.5 (GH3.5) KW - Indole-3-acetic acid (IAA) KW - Salicylic acid (SA) SP - 75 EP - 75 JF - Planta JO - Planta VL - 252 IS - 5 N2 - MAIN CONCLUSION: Exogenous SA treatment at appropriate concentrations promotes adventitious root formation in cucumber hypocotyls, via competitive inhibiting the IAA-Asp synthetase activity of CsGH3.5, and increasing the local free IAA level. Adventitious root formation is critical for the cutting propagation of horticultural plants. Indole-3-acetic acid (IAA) has been shown to play a central role in regulating this process, while for salicylic acid (SA), its exact effects and regulatory mechanism have not been elucidated. In this study, we showed that exogenous SA treatment at the concentrations of both 50 and 100 µM promoted adventitious root formation at the base of the hypocotyl of cucumber seedlings. At these concentrations, SA could induce the expression of CYCLIN and Cyclin-dependent Kinase (CDK) genes during adventitious rooting. IAA was shown to be involved in SA-induced adventitious root formation in cucumber hypocotyls. Exposure to exogenous SA led to a slight increase in the free IAA content, and pre-treatment with the auxin transport inhibitor 1-naphthylphthalamic acid (NPA) almost completely abolished the inducible effects of SA on adventitious root number. SA-induced IAA accumulation was also associated with the enhanced expression of Gretchen Hagen3.5 (CsGH3.5). The in vitro enzymatic assay indicated that CsGH3.5 has both IAA- and SA-amido synthetase activity and prefers aspartate (Asp) as the amino acid conjugate. The Asp concentration dictated the functional activity of CsGH3.5 on IAA. Both affinity and catalytic efficiency (Kcat/Km) increased when the Asp concentration increased from 0.3 to 1 mM. In contrast, CsGH3.5 showed equal catalytic efficiency for SA at low and high Asp concentrations. Furthermore, SA functioned as a competitive inhibitor of the IAA-Asp synthetase activity of CsGH3.5. During adventitious formation, SA application indeed repressed the IAA-Asp levels in the rooting zone. These data show that SA plays an inducible role in adventitious root formation in cucumber through competitive inhibition of the auxin conjugation enzyme CsGH3.5. SA reduces the IAA conjugate levels, thereby increasing the local free IAA level and ultimately enhancing adventitious root formation. SN - 1432-2048 UR - https://www.unboundmedicine.com/medline/citation/33026530/Salicylic_acid_regulates_adventitious_root_formation_via_competitive_inhibition_of_the_auxin_conjugation_enzyme_CsGH3_5_in_cucumber_hypocotyls_ L2 - https://dx.doi.org/10.1007/s00425-020-03467-2 DB - PRIME DP - Unbound Medicine ER -