The Class II LBD protein MdLBD37 positively regulates the adaptability of apples to drought and salt stress

Abstract

Lateral Organ Boundaries Domain (LBD) transcription factors are crucial for plant stress adaptation, yet their functional diversity in perennial crops remains unexplored. In this study, we characterized MdLBD37, a Class II LBD protein in apple (Malus domestica), and identified its key role in enhancing resilience to abiotic stresses. Phylogenetically clustered with anthocyanin repressors AtLBD37/38/39 from Arabidopsis thaliana, MdLBD37 exhibited conserved nuclear localization, supporting its transcriptional regulatory potential. The qRT-PCR analysis revealed that MdLBD37 expression was highest in the stems of ‘Royal Gala’ apple trees. MdLBD37 expression in apple seedlings was significantly induced by ABA, NaCl, and PEG treatments. Moreover, over-expression of MdLBD37 alleviated the growth inhibition of apple calli under PEG, NaCl, and ABA treatments, marked by increased biomass and reduced MDA accumulation, which suggested a reduction in oxidative damage. These findings not only broaden our understanding of Class II LBD proteins but also establish MdLBD37 as a promising target for developing climate-resilient apple cultivars through modulation of ABA-mediated stress signaling pathways.