Investigating leaf-environment surface modulation in apple leaves for enhancing resilience to environmental challenges

The cuticle, a hydrophobic extracellular layer that covers aerial plant organs, plays a crucial role in plant health and development. It serves as a barrier against pathogens, helps prevent water loss, shields the plant from UV radiation, and supports cellular processes essential for photosynthesis. With the epidermal cells, it forms a specialized tissue that originates from the L1 tissue layer, ensuring effective protection and adaptation to environmental conditions. This research aims to investigate the genetic mechanisms involved in biotic and abiotic stress resistance, by modulating the organization of epidermal cells and influencing the structure and composition of the cuticle. Specific genes, such as ROP and RBK, have been linked to responses to fungal infections in Arabidopsis and bacterial resistance in tomato. In Malus domestica, MdROP5 is a member of the ROP family, which functions as a molecular regulator of several cellular processes, including stress responses and development. ROP proteins cycle between an inactive GDP-bound (DN) and an active GTP-bound (CA) state. MdRBK2, a receptor-like cytosolic kinase, has been identified as an interactor of ROP GTPases in Arabidopsis. Anatomical evaluations were conducted on Gala cv. plants overexpressing either the active or inactive forms of MdROP5 and MdRBK2, revealing their influence on epidermal cell organization. In addition, previous studies have shown interactions between MdGPAT6 and the Venturia inaequalis AvrVf gene in Golden Delicious, confirmed by BiFC screening. GPAT6, a membrane-bound enzyme involved in lipid biosynthesis, regulates cutin accumulation and impacts fungal resistance in Nicotiana benthamiana and tomato. A heterologous subcellular localization study of MdGPAT6 was performed, and cisgenic Gala overexpressing MdGPAT6 were generated to assess its potential role in enhancing abiotic stress resilience in apples. These findings provide new insights into the molecular pathways regulating epidermal integrity and stress tolerance, with the potential to improve crop protection and stress resilience strategies in apple cultivation