Genome-wide analysis and functional validation of class I members of the Moso bamboo AS2 transcription factor family, and elucidation of their mechanisms of action in rapid growth, development, and under abiotic stress

AS2/LOB transcription factors are crucial for plant organ development and stress responses, but their functions in fast-growing Phyllostachys edulis remain unclear. Here, we identified 36 Class I AS2/LOB genes (PeAS2) via genome-wide analysis. Phylogenetic, motif, and gene structure analyses revealed high family conservation, while collinearity analysis indicated segmental duplication as the primary driver of expansion. Promoter analysis detected enriched cis-elements responsive to abiotic stresses (drought, salinity) and phytohormones (ABA, JA, auxin). PeAS2-04 and PeAS2-39 were highly expressed in rapidly elongating shoots and stems, and significantly upregulated under salt and drought stress. Subcellular localization confirmed PeAS2-04 localizes to the nucleus, and PeAS2-39 to both the nucleus and nuclear membrane. Yeast two-hybrid assays demonstrated specific interactions among Class I members. Heterologous overexpression of PeAS2-04 and PeAS2-39 in Arabidopsis induced typical adaxial–abaxial polarity defects, including dwarfism and upward leaf curling, while markedly enhancing primary root elongation. Transgenic seeds showed significantly higher germination rates than wild-type under salt or drought stress. These findings indicate PeAS2-04 and PeAS2-39 are functional orthologs of Arabidopsis AS2, involved in leaf polarity, root development, and abiotic stress tolerance, providing novel insights for bamboo molecular breeding.