<i>ZmLBD42</i> coordinates cell proliferation and organogenesis to enhance somatic embryogenesis and regeneration in maize

The genotype-dependent recalcitrance of maize somatic embryogenesis necessitates key regulatory gene identification. However, the efficiency and genotype-dependence of somatic embryogenesis, especially in major cereal crops like maize, remain a challenge. Here, through integrated bioinformatics screening, spatiotemporal expression profiling, and comprehensive genetic functional validation in both heterologous Arabidopsis and homologous maize systems, we identify that LATERAL ORGAN BOUNDARIES DOMAIN (LBD) transcription factor ZmLBD42 acts as a positive regulator of embryogenic callus morphogenesis, organogenic differentiation, and plantlet regeneration competence. Heterologous overexpression of ZmLBD42 in Arabidopsis enhanced callus biomass and projected area from root and leaf explants. Loss-of-function maize mutants (Mu transposon insertion zmlbd42-mu and CRISPR-Cas9-generated zmlbd42-crispr) showed severe proliferative defects, including reduced callus biomass accumulation and impaired cellular architecture characterized by enlarged cells and reduced cell density. zmlbd42 mutants displayed compromised organogenic competence, with lower greening callus formation and reduced regeneration efficiency. Moreover, ZmLBD42 overexpression in maize enhances callus induction rates, accelerates differentiation initiation, and elevates plantlet regeneration efficiency by 102.31% in maize. These results establish ZmLBD42 as an integrator that potentiates somatic reprogramming through coordinated modulation of cell proliferation, light-responsive organogenesis, and plantlet regeneration, providing a strategic target for improving genetic transformation and regeneration efficiency in maize.