Beyond FERONIA: Gene Expression Profiling Reveals Functional Diversification of Malectin/Malectin-Like Proteins in Tissues with Cell Walls Differing in Pectin Content

Malectin and malectin-like proteins (M/MLPs) form one of the largest plant lectin families, yet the carbohydrate specificity of most members remains largely unexplored. FERONIA, a receptor-like kinase and key regulator of cell expansion, is the best-known member experimentally confirmed to bind pectins. Using transcriptomic data from plant species with contrasting cell wall pectin contents-Arabidopsis thaliana, maize (Zea mays), celery (Apium graveolens), and flax (Linum usitatissimum)-we revised all M/MLP genes and analyzed their expression profiles, alongside genes encoding glycosyltransferases (GTs) involved in cell wall polysaccharide biosynthesis. Distinct sets of M/MLPs were upregulated during cell expansion, in pectin-rich tissues, and during wall thickening, with only partial overlap between orthologs of monocots and dicots. A strong coexpression of M/MLP genes with those encoding GTs associated with pectin biosynthesis was found in celery, whereas M/MLPs expressed in flax fibers with tertiary walls exhibited little correlation. In contrast, almost all M/MLP genes in all analyzed samples showed no or negative expression correlation with genes encoding GTs for xyloglucan and cellulose biosynthesis. These results indicate functional specialization within the M/MLP family and highlight candidate genes for future studies on pectin recognition and cell wall sensing.