Stem-cell-expressed DEVIL-like small peptides maintain root growth under abiotic stress via abscisic acid signaling.

Stem cells are essential to plant growth and development. Through data mining, we identified five DEVIL-like (DVL) small peptide genes that are preferentially expressed in the quiescent center (QC) of Arabidopsis (Arabidopsis thaliana) root but whose functions are unknown. When overexpressed, these genes caused a dramatic decrease in root length and pleiotropic phenotypes in the shoot. No root growth defect was observed in the single gene mutants, but the quintuple mutant exhibited slightly longer roots than the wild type. Through transcriptome analysis with DVL20-overexpressing plants, we found that many genes involved in abscisic acid (ABA) signaling were regulated by these peptides. Consistent with this finding, we demonstrated that, relative to the wild type, DVL20-overexpressing plants were more tolerant whereas the quintuple mutant was more sensitive to ABA. Using RT-qPCR, we showed that ABA signaling-associated genes were affected in an opposite manner when the plants were grown in normal or ABA-containing medium. Strikingly, ectopic expression of ABA signaling genes such as PYRABACTIN RESISTANCE 1-LIKE (PYL) 4, 5 or 6 or suppression of HIGHLY ABA INDUCED 2 (HAI2) and MITOGEN-ACTIVATED PROTEIN KINASE KINASE KINASE 18 (MAPKKK18) not only largely rescued the root growth defects in DVL20-overexpressing plants in normal growth condition but also conferred tolerance to ABA. Based on these results, we propose that DVL1, 2, 5, 8 and 20 function redundantly in root stem-cell maintenance under abiotic stress, and this role is achieved via ABA signaling.