Background:
Anoectochilus roxburghii (Wall.) Lindl. (
A. roxburghii) was widely used in traditional Chinese medicine and also as a health food in China. Gibberellins (GAs) are plant hormones that regulate various aspects of growth and development in
A. roxburghii. Ent-kaurene synthase (KS) plays a crucial role in the biosynthesis of GAs in plants. However, there is limited functional analysis of KS in GA biosynthesis and its effect on salt tolerance, especially in
A. roxburghii.
Methods: The
ArKS genes were cloned from
A. roxburghii, and its salt tolerance characteristics were verified by prokaryotic expression. Under salt stress, analyze the regulation of
KS gene on GA and active ingredient content by qRT-PCR and HPLC-MS/MS, and explore the mechanism of exogenous GAs promoting active ingredient enrichment by regulating the expression level of the
KS under salt stress.
Results: The
ArKS protein was highly homologous to KSs with other plant species; subcellular localization of KS protein was lacking kytic vacuole. The transformants displayed a significant increase in salt tolerance under the stress conditions of 300 mM NaCl. And the expression of
ArKS genes and the GAs accumulation was downregulated under the salt stress; among them, the contents of GA3, GA7, GA8, GA24, and GA34 showed a significant decrease. It was further found that there was an increase (1.36 times) in MDA content and a decrease (0.84 times) in relative chlorophyll content under the salt conditions from
A. roxburghii. However, the content of active constituents was elevated from
A. roxburghii under the NaCl stress, including polysaccharides, total flavonoids, and free amino acids, which increased by 1.14, 1.23, and 1.44 times, respectively. Interestingly, the
ArKS gene expression and the chlorophyll content was increased, MDA content showed a decrease from 2.02 μmoL·g
−1 to 1.74 μmoL·g
−1 after exogenous addition of GAs, and the elevation of active constituents of polysaccharides, total flavonoids, and free amino acids were increased by 1.02, 1.09, and 1.05 times, implying that GAs depletion mitigated the damage caused by adversity to
A. roxburghii.
Conclusions: The
ArKS gene cloned from
A. roxburghii improved the salt tolerance of plants under salt stress by regulating GA content. Also, GAs not only alleviate salt tolerance but also play a key role in the synthesis of active components in
A. roxburghii. The functions of
KS genes and GAs were identified to provide ideas for improving the salt tolerance and quality of ingredients in artificial cultivation from
A. roxburghii.
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