Phytohormone and transcriptome analyses reveal the mechanisms underlying branch inclination angle formation in narrow-crowned Chamaecyparis hodginsii

A study of 14 provenances of the narrowly crowned form of Chamaecyparis hodginsii identified provenances 3 and 4 as the most promising sources for narrow-crowned traits and found that auxin levels and several phytohormone pathways were associated with branch inclination angle. The study combined measurements of endogenous hormones, assessment of variation among provenances, path analysis and transcriptome profiling to examine the physiological and molecular correlates of branch architecture.

Provenance 4 had the lowest mean branch inclination angle, while provenance 2 had the highest proportion of narrow-crowned individuals and the highest measured zeatin levels. Auxin, or indole-3-acetic acid, was lowest in provenance 14. Across the 14 provenances, branch inclination angle was significantly negatively correlated with both zeatin and indole-3-acetic acid. Path analysis indicated a strong negative direct effect of indole-3-acetic acid on branch inclination angle. These findings describe statistical and model-based relationships among the measured variables; the abstract does not report experimental manipulation or direct functional testing of the proposed mechanism.

The transcriptome analysis identified 2,272 differentially expressed genes, including 27 associated with phytohormone signaling pathways. Six members of the SAUR family were up-regulated and three were down-regulated in the narrow-crowned provenance, with distinct expression patterns suggesting that they may participate in auxin-signaling output during branch inclination angle development. Cytokinin regulators A-ARR and B-ARR showed opposite expression patterns. The gibberellin receptor GID1 was down-regulated and the growth-repressor DELLA was up-regulated, which the authors interpreted as consistent with reduced promotion of cell division and elongation.

Additional expression differences were reported in salicylic acid, jasmonic acid, abscisic acid and ethylene signaling. Genes in salicylic acid and jasmonic acid signaling were suppressed, the abscisic acid regulator PP2C decreased and the ethylene-associated component EIN2 increased. The authors interpreted this pattern as evidence of reprogramming in defense-related phytohormone signaling. They concluded that auxin and downstream SAUR genes may be important in regulating branch inclination angle and that provenances 3 and 4 warrant attention as narrow-crowned sources. However, the supplied evidence is an abstract from an early, accepted manuscript subject to further edits; it does not provide detailed sampling methods, effect sizes, uncertainty estimates or functional validation, so the specific molecular mechanisms and breeding implications remain bounded by the reported comparative analysis.

Subject of Research: Provenance-associated phytohormone and gene-expression patterns underlying branch inclination angle variation in Chamaecyparis hodginsii

Article Title: Phytohormone and transcriptome analyses reveal the mechanisms underlying branch inclination angle formation in narrow-crowned Chamaecyparis hodginsii

Article References: Cai, X., Chen, Z., Bai, J., Xiao, J., Liu, J., Lin, Y., Lin, Y., Lu, B., Gao, T., Chen, L., He, T., Chen, L., Rong, J., & Zheng, Y. (2026). Phytohormone and transcriptome analyses reveal the mechanisms underlying branch inclination angle formation in narrow-crowned Chamaecyparis hodginsii. BMC Plant Biology. https://doi.org/10.1186/s12870-026-10049-z

Image Credits: AI Generated

DOI: 10.1186/s12870-026-10049-z

Keywords: Chamaecyparis hodginsii, branch inclination angle, narrow-crowned provenances, auxin, zeatin, SAUR genes, cytokinin signaling, transcriptome analysis, phytohormones, forest tree breeding, Phytohormone, transcriptome