Integrated transcriptomic, untargeted and targeted metabolomic analyses reveal seasonal regulatory mechanisms of vascular cambium activity in woody plants: insights from Schima superba

TL;DR

This study explores how the vascular cambium in Schima superba changes seasonally by combining gene and metabolite analyses, revealing key regulatory mechanisms for wood formation.

Contribution

The study integrates transcriptomic and metabolomic data to uncover seasonal regulatory mechanisms of cambium activity in a woody plant.

Findings

Key genes in phenylpropanoid biosynthesis peak during active cambial periods, correlating with lignin accumulation.

Plant hormone signaling genes show stage-specific expression patterns that regulate cambial cell expansion and division.

Core transcription factors like SsMYB and SsGRAS are identified as regulators of seasonal cambial activity.

Abstract

The vascular cambium is a pivotal tissue that drives secondary growth in woody plants, directly determining wood structure and properties. Schima superba, a valuable timber species in China, holds considerable ecological and economic importance. However, the seasonal activity of its cambium remains poorly understood.

To elucidate the underlying molecular and metabolic regulatory mechanisms, we integrated untargeted metabolomics, lignin-targeted metabolomics, and transcriptomic analyses.

Untargeted metabolomic profiling identified 2,178 differentially synthesised metabolites (DSMs), predominantly associated with amino acid metabolism, fatty acid metabolism, phenylpropanoid biosynthesis (PB), and plant hormone signal transduction (PHST). Lignin-targeted metabolomics detected 8 DSMs, most of which initially increased and subsequently declined, peaking in August, with the exception of sinapyl alcohol and L-phenylalanine. Transcriptomic analysis identified 19,609 differentially expressed genes (DEGs), primarily enriched in PB and PHST pathways. Key PB-related structural genes, including SsPAL, SsC4H, Ss4CL, SsCOMT, and SsCAD, exhibited peak expression during the cambial active period, correlating with lignin intermediate accumulation and indicating tight coordination between transcriptional activity and metabolic flux during lignification. PHST-related genes involved in auxin (AUX), cytokinin (CTK), and gibberellin (GA) signalling, such as SsARF, SsSAUR, and SsARR-B, displayed stage-specific expression patterns regulating cambial cell expansion and division. Weighted gene coexpression network analysis (WGCNA) further identified core transcription factors, including SsMYB, SsbHLH, SsWOX, SsGRAS, SsSAUR, and SsNF-YB, as regulators of seasonal cambial activity.

These findings provide a comprehensive framework for understanding seasonal cambial activity in S. superba, and offer valuable insights into the regulatory mechanisms of vascular cambium activity in woody plants, thereby supporting targeted wood quality improvement and advancing our understanding of plant developmental biology.

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