Regulates Arabidopsis Stem Secondary Wall Development.

Wall-associated kinases/kinase-likes (WAKs/WAKLs) are plant cell surface sensors. A variety of studies have revealed the important functions of WAKs/WAKLs in regulating cell expansion and defense in cells with primary cell walls. Less is known about their roles during the development of the secondary cell walls (SCWs) that are present in xylem vessel (XV) and interfascicular fiber (IF) cells. In this study, we used RNA-seq data to screen WAKs/WAKLs members that may be involved in SCW development and identified as a candidate. We obtained T-DNA insertion mutants (inserted at the promoter region) and (inserted at the first exon) and compared the phenotypes to wild-type (WT) plants. Decreased transcript levels in stems were found in the mutant plants, and the phenotypes observed included reduced stem length and thinner walls in XV and IFs compared with those in the WT plants. Cell wall analysis showed no significant changes in the crystalline cellulose or lignin content in mutant stems compared with those in the WT. We found that had alternative spliced versions predicted to have only extracellular regions, which may interfere with the function of the full-length version of . Our results suggest WAKL8 can regulate SCW thickening in Arabidopsis stems.