<scp>BpMYB73</scp> regulates long noncoding <scp>RNA</scp> <i>BplncW20</i> to improve drought tolerance by mediating <scp>ROS</scp> scavenging in <i>Betula platyphylla</i>

Summary Drought severely limits tree growth. While long noncoding RNAs (lncRNAs) are crucial to plant stress responses, their mechanisms in drought adaptation remain unclear. Using RNA‐seq, chromatin immunoprecipitation, yeast one‐hybrid, electrophoretic mobility shift assay, chromatin isolation by RNA purification, and dual‐luciferase reporter assays, we investigated the molecular mechanism by which the drought‐inducible lncRNA BplncW20 regulates drought responses in Betula platyphylla (birch). Under normal conditions, BplncW20 overexpression (OE) promoted root growth, increased the root‐to‐shoot ratio, and reduced plant height without affecting biomass; under drought stress, it enhanced root development, biomass, root‐to‐shoot ratio, and drought tolerance, whereas the bplncw20 # mutants showed opposite phenotypes. BplncW20 significantly activated key genes involved in water deprivation and hydrogen peroxide response pathways. It upregulated BpFSD2 expression by binding to its promoter, thereby enhancing antioxidant capacity and reducing the accumulation of reactive oxygen species and malondialdehyde. The transcription factor BpMYB73 acted as an upstream regulator of BplncW20 , binding to MYB Binding Site (MBS) and abscisic acid‐responsive element cis ‐elements in the BplncW20 promoter to initiate its transcription. Overexpressing BpMYB73 enhances root development and drought tolerance, similar to BplncW20 OE plants. This study proposed a putative regulatory pathway of BpMYB73‐MBS/ABRE‐ BplncW20 ‐target genes, revealing the critical role of BplncW20 in root development and drought adaptation.