Unravels Regulatory Mechanism of Polysaccharide Biosynthesis in Dendrobium officinale

As a precious medicinal herb, Dendrobium officinale is rich in bioactive mannans. Studies indicate that these mannans possess antioxidant properties, enhance immune function, and ameliorate type II diabetes. However, the molecular regulatory mechanisms governing mannan biosynthesis remain unclear, significantly impeding the genetic improvement and large-scale application of this plant.

The research team led by HE Chunmei at the South China Botanical Garden of the Chinese Academy of Sciences has deciphered the molecular regulatory model for mannan biosynthesis in Dendrobium officinale, revealing the pivotal role of the ERF5-WOX4 transcription factor regulatory module in this process. These findings provide crucial genetic resources and a theoretical foundation for breeding new varieties and advancing the utilization of Dendrobium.

Using the promoter of DoGMP1—a key gene in the polysaccharide synthesis pathway—as bait, the research team identified DoWOX4 as a candidate transcription factor through yeast one-hybrid (Y1H) library screening. Further experiments confirmed that DoWOX4 directly binds to the DoGMP1 promoter and activates its expression: overexpression of DoWOX4 enhanced mannan accumulation, while silencing DoWOX4 suppressed DoGMP1 expression and mannan synthesis. Additionally, the ethylene-responsive factor DoERF5 was found to bind to the DoWOX4 promoter, negatively regulating DoWOX4 expression and thereby inhibiting mannan biosynthesis. Based on these results, the team proposed the "ERF5-WOX4 regulatory model": DoWOX4 promotes mannan synthesis by activating DoGMP1, while DoERF5 suppresses this pathway by downregulating DoWOX4 and DoGMP1 expression. This breakthrough not only resolves long-standing questions about the molecular regulation of mannan biosynthesis but also opens avenues for the molecular breeding of high-value Dendrobium varieties.

This work was supported by the Science and Technology Projects of Guangzhou, the National Natural Science Foundation of China, the Key-Area Research and Development Program of Guangdong Province, and the Guangdong Science and Technology Plan Project. Link to the article: https://doi.org/10.1093/plphys/kiaf273

Figure. A working model of ERF5-WOX4 regulating mannan biosynthesis in Dendrobium officinale.

（Imaged by HE et al）