Structural, genetic, and adaptive basis of superhydrophobicity in rice leaves

In most plants, leaf surfaces exhibit water-repellent properties, which protect against pathogens and weather. Plants such as lotus and rice have evolved outstanding water-repellent properties, termed superhydrophobicity (static contact angle >150°). However, the structural and genetic basis of these properties in crop plants remains unclear. In this study, water repellency was quantified by measuring static contact angles, and its relationship with epicuticular wax load, the extent of wax coverage assessed by scanning electron microscopy, and the differentiation of papillae was analyzed in a large collection of rice wetting-leaf mutants and diverse cultivars, as well as wild Oryza species. Analysis of leaf surface structure in mutants derived from cultivated rice revealed that the degree of water repellency largely depends on the cuticular wax quantity and quality. Although papillae differentiation contributes minorly to water repellency, it is suggested to play a crucial role in achieving superhydrophobicity. These morphological characteristics are regulated by at least 5 previously characterized genes. Furthermore, we found that superhydrophobicity is widely conserved among cultivated rice and is also present in ancestral species. These observations suggest that superhydrophobicity evolved independently of rice domestication. These findings provide a structural and genetic framework for understanding the evolution and potential adaptive significance of leaf superhydrophobicity in rice and offer insights for engineering leaf-surface traits relevant to crop resilience and management.