Integrative multi-omic analysis identifies genes associated with cuticular wax biogenesis in adult maize leaves

Studying the genetic basis of leaf wax composition and its correlation with leaf cuticular conductance ( g c) is crucial for improving crop water-use efficiency. The leaf cuticle, which comprises a cutin matrix and various waxes, functions as an extracellular hydrophobic layer, protecting against water loss upon stomatal closure. To address the limited understanding of genes associated with the natural variation of leaf cuticular waxes and their connection to g c, we conducted statistical genetic analyses using leaf transcriptomic, metabolomic, and physiological data sets collected from a maize ( Zea mays L.) panel of ∼300 inbred lines. Through a random forest analysis with 60 cuticular wax traits, it was shown that high molecular weight wax esters play an important role in predicting g c. Integrating results from genome-wide and transcriptome-wide studies (GWAS and TWAS) via a Fisher’s combined test revealed 231 candidate genes detected by all three association tests. Among these, 11 genes exhibit known or predicted roles in cuticle-related processes. Throughout the genome, multiple hotspots consisting of GWAS signals for several traits from one or more wax classes were discovered, identifying four additional plausible candidate genes and providing insights into the genetic basis of correlated wax traits. Establishing a partially shared genetic architecture, we identified 35 genes for both g c and at least one wax trait, with four considered plausible candidates. Our study uncovered the genetic control of maize leaf waxes, establishing a link between wax composition and g c, with implications for potentially breeding more water-use efficient maize. SIGNIFICANCE STATEMENT We exploited natural variation in the abundance of maize leaf cuticular waxes to identify genetic determinants of wax composition and its relationship to cuticle function as a barrier against water loss. We identified a set of strongly supported candidate genes with plausible functions in cuticular wax biosynthesis or deposition and added to the evidence for wax esters as the most important wax for water barrier function, offering new tools for modification of cuticle-dependent traits. ### Competing Interest Statement The authors have declared no competing interest.