MYB46 integrates cuticle and cell wall remodeling to coordinate drought tolerance and pathogen resistance in Arabidopsis

The plant cuticle and cell wall form a dynamic barrier against environmental stresses. While MYB46 is a known regulator of secondary cell wall biosynthesis, its role in cuticle formation and the interplay between these two structural barriers in stress responses remained unexplored. This study investigated whether MYB46 modulates cuticle biosynthesis and permeability, influencing drought tolerance and pathogen resistance in Arabidopsis. We generated MYB46 loss-of-function mutants (myb46-3, myb46-4) and overexpression lines. Cuticle permeability, cutin/wax compositions in stems and leaves, and associated gene expression profiles and direct transcriptional regulation by MYB46 were analyzed. MYB46 mutants exhibited reduced cutin/wax accumulation and increased cuticle permeability. This led to enhanced resistance to Botrytis cinerea via upregulation of defense-related genes (e.g. cell wall-bound peroxidases and PAD3) but resulted in decreased drought tolerance. Conversely, MYB46 overexpression reinforced cuticle integrity, increased cutin/wax accumulation, and improved drought tolerance without affecting disease susceptibility. MYB46 directly activated cuticle biosynthesis genes (LACS1, LACS2, KCS1, KCS19, CER1), linking it to cuticle regulation. These findings establish MYB46 as a dual regulator integrating cuticle and cell wall remodeling, balancing structural defense against pathogens with adaptive responses to drought. This highlights its pivotal role in coordinating stress adaptation mechanisms in Arabidopsis.