The peptidyl-prolyl isomerases FKBP15-1 and FKBP15-2 negatively regulate lateral root development by repressing a vacuolar invertase in Arabidopsis

Background Lateral root (LR) architecture determines the efficiency of nutrient absorption and anchors the plant. Internal auxin regulatory mechanisms that control the development of LR have been identified, but how external nutrients influence lateral root development remains elusive. Results We have characterized the functions of the FK506-binding proteins FKBP15-1 and FKBP15-2 in Arabidopsis. FKBP genes are mainly expressed in the vascular bundle of the root basal meristem region, and the FKBP proteins are localized to the endoplasmic reticulum. Co-IP and BIFC assays showed that FKBP15-1 and FKBP15-2 interact with the vacuolar invertase 2 (VIN2). Compared to Col-0 and the single mutants, the double mutant fkbp15-1fkbp15-2 had more LRs and LR initiation density, and possessed higher sucrose catalytic activity. Moreover, VIN2 can complement the phenotype of increased LRs in the fkbp15-1fkbp15-2 double mutant. Conclusion Our results indicate that FKBP15-1 and FKBP15-2 together participate in the control of LR numbers by regulating the enzyme activity of VIN2. Due to the activity of peptidylprolyl cis-trans isomerases owned by FKBP family proteins, our results provide a clue to further analysis the interplay between lateral root development and protein modification.