Dendrobium officinale, a prized medicinal herb, is valued for its bioactive mannans—compounds with documented antioxidant effects, immune-enhancing properties, and potential to alleviate type II diabetes. However, the molecular mechanisms regulating mannan biosynthesis in the plant have long remained elusive.

A research team led by Prof. HE Chunmei from the South China Botanical Garden of the Chinese Academy of Sciences, has now unraveled this regulatory process, identifying a key transcription factor module—ERF5 (ethylene-responsive transcription factor 5)-WOX4 (WUSCHEL-related homeobox)—that plays a key role in mannan production. 

Their findings were recently published in the journal Plant Physiology.

The study centered on DoGMP1, a critical gene in the polysaccharide synthesis pathway. Using the DoGMP1 promoter as a bait, the researchers employed yeast one-hybrid (Y1H) library screening to identify DoWOX4 as a candidate transcription factor that interacts with this gene. Follow-up experiments confirmed that DoWOX4 directly binds to the DoGMP1 promoter, activating its expression. Functional tests further validated its role: overexpression of DoWOX4 boosted mannan accumulation, while silencing the gene suppressed both DoGMP1 expression and mannan synthesis.

The team also discovered that DoERF5 binds to the DoWOX4 promoter, exerting a negative regulatory effect. By downregulating DoWOX4 expression, DoERF5 indirectly inhibits mannan biosynthesis.

Based on these results, the researchers proposed an "ERF5-WOX4 regulatory model": DoWOX4 promotes mannan synthesis by activating DoGMP1, while DoERF5 counteracts this process by suppressing DoWOX4—and consequently DoGMP1—expression.

This breakthrough not only resolves a gap in mannan biosynthesis regulation but also lays the groundwork for molecular breeding strategies to develop high-value Dendrobium varieties with enhanced mannan content, the researchers noted.

This study was supported by funding from the Science and Technology Projects of Guangzhou, the National Natural Science Foundation of China, and other sources.

A working model of ERF5-WOX4 regulating mannan biosynthesis in Dendrobium officinale. (Imaged by HE Chunmei et al)