Arabidopsis mucilage has been used for more than two decades to investigate and characterize different factors of pectin synthesis and modification. Using cytological, transcriptomic, chemical, and molecular approaches, Zhang et al. (2022) clarify the redundant role of KNAT3 and KNAT7, two KNOX Class II transcription factors, in mucilage rhamnogalacturonan-I (RG-I) biosynthesis through the regulation of a group of genes which coordinate the formation of these specificpectic domains.