Phenotypic and transcriptomic analysis reveals key genes associated with plant height in rubber tree and functional characterization of the candidate gene <i>HbFLA11</i>

The rubber tree (Hevea brasiliensis) is an important species in global natural rubber production. However, the mechanisms regulating the height of rubber trees remain poorly understood. In previous work, the dwarf mutant MU73397 was obtained through ethyl methanesulfonate mutagenesis. Compared to the wild-type CATAS73397, MU73397 exhibited significantly reduced plant height and stem diameter, slower xylem development, and decreased cellulose and lignin content. Phytohormone analysis revealed that gibberellin levels were reduced in both the apex and stem of MU73397, while jasmonic acid was increased in the apex and auxin was reduced in the stem. These differences in hormone levels may contribute to the dwarf phenotype. Transcriptome analysis identified nine key genes related to cell wall biosynthesis and hormone signaling, namely, FLA11 (Fasciclin-like arabinogalactan protein 11), TUBB1 (Tubulin Beta 1), TUBB6 (Tubulin Beta 6), CESA7 (cellulose synthase A 7), TUBA4 (Tubulin Alpha 4), LAC17 (Laccase 7), CTL2 (Chitinase-like protein 2), IRX9 (Irregular xylem 9), and KOR (korrigan). Overexpression of HbFLA11 in transgenic poplar resulted in significant increases in plant height and stem diameter. Gibberellin signaling genes and cell wall biosynthesis genes were significantly upregulated in the transgenic lines. These results suggest that HbFLA11 is involved in gibberellin signaling and cell wall biosynthesis, thereby regulating plant growth. This study provides valuable genetic resources and research foundations for targeted trait breeding in rubber tree.