PlantView Supports Xylem Cell Expansion Research: The LkMTA2/LkMTB8–LkERF1–LkEXPA8 cascade regulates xylem cell expansion in larch

Recently, the research group led by Xiaomei Sun at the Research Institute of Forestry, Chinese Academy of Forestry, made new progress in elucidating the molecular regulatory mechanisms underlying xylem cell expansion in Japanese larch. The findings were published in the “New Phytologist” (IF = 8.1, top journal).

This study revealed the molecular mechanism by which m⁶A RNA modification regulates xylem cell expansion in Japanese larch and identified the LkMTA2/LkMTB8–LkERF1–LkEXPA8 cascade as a key regulatory pathway, providing new insights into the regulatory network of wood formation and offering valuable candidate genes for genetic improvement of wood quality.

Wood formation is a critical process in tree growth and development, and the xylem cell expansion stage directly determines the final size and morphology of wood cells, thereby influencing both wood yield and quality. Previous studies have demonstrated that enzymes such as expansins (EXPs) and transcription factors such as ethylene response factors (ERFs) participate in regulating this process. Epigenetic modifications are also known to play important roles in xylem development; however, the contribution of post-transcriptional regulation, particularly RNA methylation, to xylem cell expansion remains poorly understood. As the most abundant internal modification in eukaryotic mRNA, N6-methyladenosine (m⁶A) regulates plant growth and development by affecting mRNA stability and translation efficiency. Although the functions of m⁶A methyltransferase complexes, including MTA and MTB, have been well characterized in model plants, their roles in xylem development of woody species remain largely unexplored. Japanese larch is an important timber and afforestation tree species, and the molecular mechanisms governing its xylem development require further investigation. Therefore, exploring the role of m⁶A modification and its regulatory network in xylem cell expansion is of great significance for understanding wood formation and facilitating forest tree genetic improvement.

This study demonstrated that treatment with the m⁶A methyltransferase inhibitor STM2457 induced global m⁶A hypomethylation in Japanese larch and significantly increased the cross-sectional area of xylem cells. The researchers further found that LkMTA2 and LkMTB8 form a heterodimer that enhances the stability of LkERF1 mRNA through m⁶A modification, thereby promoting LkERF1 expression. LkERF1 directly binds to the promoter of LkEXPA8, a key gene involved in xylem cell expansion, and represses its transcription, ultimately inhibiting xylem cell expansion. Moreover, overexpression of LkMTA2, LkMTB8, or LkERF1 in poplar reduced the cross-sectional area of vessel lumens, further confirming the conserved function of this regulatory pathway. This work establishes, for the first time, a molecular link between m⁶A RNA modification and xylem cell expansion in woody plants, providing a new perspective for understanding the regulatory network of wood formation and offering important theoretical support for wood quality improvement.

Experiments using Plantview

The PlantView in vivo plant imaging system developed by Biolight Biotechnology was employed in this study to perform luciferase complementation imaging (LCI) assays. The results confirmed a direct interaction between LkMTA2 and LkMTB8 in vivo.

DOI: 10.1111/nph.71021