A research team led by Prof. WU Lifang from the Hefei Institutes of Physical Science of the Chinese Academy of Sciences has uncovered the stage-specific regulatory roles of plant hormones, particularly exogenous trans-zeatin (tZ), in the development of axillary bud in Eucommia ulmoides, a high-value economic crop.

The findings were recently published in Industrial Crops and Products.

Eucommia ulmoides, valued for its medicinal, nutritional, and rubber-producing properties, has been the subject of increasing research attention. While recent studies have focused mainly on its medicinal ingredients and rubber properties, the molecular mechanisms governing its growth and development remain poorly understood. In particular, how external plant growth regulators affect its regeneration and development in vitro remains an urgent question.

Building upon their previously established efficient regeneration system for E. ulmoides, the researchers investigated the role of exogenous tZ, a type of cytokinin, in regulating axillary bud development. They collected axillary bud samples at five different developmental stages and conducted integrated targeted metabolomics and transcriptomic analyses.

Their analysis revealed that axillary bud development in E. ulmoides proceeds through two primary phases: the initial induction phase (W0–W1) and the subsequent elongation phase (W1–W4). Dynamic changes in hormone levels and gene expression patterns were observed under tZ treatment, offering insights into the stage-specific regulatory mechanisms.

Using weighted gene co-expression network analysis (WGCNA), the researchers identified key hormone-related gene modules and constructed a regulatory network illustrating hormone crosstalk during axillary bud growth.  

"The network shows how plant hormones talk to each other during bud growth," said Dr. WANG Dacheng, a member of the team. 

This work lays a theoretical foundation for deciphering the molecular mechanisms by which cytokinins regulate in vitro regeneration and growth in E. ulmoides, according to the team.

Common regulatory network in hormone signaling pathways and zeatin biosynthesis pathway on axillary bud development of E. ulmoides. (Image by WANG Dacheng)