Uncovers the regulatory mechanism of cytokinin-induced accumulation of secondary metabolites in Santalum album heartwood

Indian sandalwood(Santalum album) is a small tropical tree in the Santalaceae. This species is the most important species in the Santalumgenus owing to its high quality essential oil (EO) in heartwood, whichis widely utilized in the perfume industry andmedical field. The EO contains (Z)-α-santalol and (Z)-β-santalol, accounting for more than 80% of the totalEO content. Heartwood, in which EO is synthesized and accumulates, usually takes 6-8 years to form under natural growth conditions. EO content inthe HW of 30-year-old trees meets international standards. With the increasing demand for sandalwood, how to improve the production of EO and other secondary metabolites in sandalwood has become a research hotspot.

The study found that the levels of terpenoids, total flavonoids and phenolics significantlyincreased after cytokinin(6-benzyladenine, BA)treatment. Prominently, the content of santalols was increased by approximately 90-fold by BA relative to the control and was associated with the contents of flavonoids and phenolics, displaying similar profiles to those detected innatural heartwood from 10-year-old trees. Further studies revealed that exogenously appliedBA positively participated in the biosynthesis of sandalwood EO by interacting with other hormones like JA and ethylene.In summary, BA as a powerful elicitor, activated cambial differentiation to form heartwood but also promoted the accumulations of secondary metabolites in S. album stems.

The current work represents the first report on the regulatory mechanism of exogenous hormone-induced production of secondary metabolites in heartwood of a tree species. This study provides valuable insight for developing a highly promising strategy for rapidly augmenting the contents of useful secondary metabolitesto obtain economic benefits.

The research was funded by the National Natural Science Foundation of China, the Guangzhou Science and Technology Program and the Guangdong Provincial Key Research and Development Program. The paper can be accessed at: https://doi.org/10.1016/j.indcrop.2024.120285

Figure . Elucidation of the regulatory mechanism of cytokinin-induced accumulation of secondary metabolites in Santalum album heartwood.(Image by CHEN et al)