TNF performed morphological analyses and, with BMK, IM, and EG, was involved in cell wall analyses. of changes to cell wall polysaccharides in the mutants. Conclusions LRX3, LRX4, and LRX5, and most likely LRX proteins in general, are important for cell wall development. Due to the complexity of changes in cell wall structures in the mutants, the exact function of LRX proteins remains Neurog1 to be determined. The increasingly strong growth-defect phenotypes in double ATB-337 and triple mutants suggests that the LRX proteins have similar functions and that they are important for proper herb development. Electronic supplementary material The online version of this article (doi:10.1186/s12870-015-0548-8) contains supplementary material, which is available to authorized users. that show changes in cell morphology (for review, see [2]). Plants have developed a sophisticated system to monitor cell wall formation in order to respond to changes in cell wall composition [2C5]. Genetic approaches have led to the identification of a number of receptor-like transmembrane proteins that perceive signals from the cell wall and transduce them to the cytoplasm. Wall-associated kinases have a cytoplasmic kinase domain name and an extracellular domain name that can bind pectin, and serve functions in pathogen response as well as regulation of osmotic pressure [6C9]. encodes a CrRLK-like receptor kinase that monitors changes in the cell wall caused by a reduced cellulose content and induces secondary changes in the cell wall such as lignin deposition [10, 11]. Leucine-rich repeat (LRR) proteins have been identified in a number of systems to act as interaction partners in either a signaling cascade or as modulators of protein activity. Polygalacturonase inhibitors (PGIPs) specifically bind polygalacturonases, thereby inhibit their enzymatic function, and thus influence the turnover ATB-337 of pectic polysaccharides [12]. Pathogen-recognizing disease resistance proteins often contain an LRR domain name which is usually thought to interact with a pathogen-induced molecule [13]. On the other hand, the brassinosteroid and auxin binding proteins BRI and TIR1 harbour LRR domains [14, 15], revealing the broad chemical spectrum of potential binding partners of LRR domains. Out of over 200 LRR-receptor proteins encoded in Arabidopsis, some have been shown to be important for cell wall developmental processes. and influence cell wall function and cell growth properties by affecting cell wall composition [16]. LRR-extensin (LRX) proteins are extracellular proteins found in different plant species [17, 18]. LRX proteins contain an N-terminal LRR domain name with 10 complete LRRs, and a C-terminal extensin domain name with (Ser-Hyp4)-made up of repetitive motifs common for this class of HRGPs [19, 20]. While the LRR domain name is usually well conserved among LRX proteins, the extensin domain name is usually variable [17]. Many structural cell wall proteins, including extensins, are able to covalently crosslink in the cell wall and thereby influence mechanical properties [21C23]. For LRX1 of ATB-337 and are paralogous genes and are predominantly expressed in root hairs where they function synergistically during cell development. double mutants show a severe defect in root hair cell wall structures and growth, suggesting a role of LRX1 and LRX2 in cell wall formation [24, 26]. To better understand the function of LRX proteins during cell wall development, it is desirable to characterize the changes in cell wall structures and composition induced by mutations in genes. Root hairs present a suboptimal cell type for these analyses due to their low abundance and atypical (for herb cells) tip growing mode of growth. and are paralogs and share an almost identical expression profile [17]. Together, it can be hypothesized that these three LRX proteins have similar functions in overlapping ATB-337 tissues. In this work, the characterization of is usually described. Single, double, and triple mutants established using T-DNA insertion mutants reveal synergistic mutant phenotypes, suggesting a similar function of these three genes. The changes in cell wall composition observed in the mutant lines compared to the wild type indicate that LRX proteins indeed have a function in cell wall formation. The lack of these proteins induces not only changes.