The 30th International Conference on Arabidopsis Research (ICAR 2019)

440 / 2019-02-05 11:04:45

A mechanism coordinating root growth, endodermal specification and redox homeostasis in Arabidopsis thaliana

SCARECROW,Cell elongation,ABA,UPB1,Root growth,Redox

Plenary track > Development

Root growth relies on both cell division in the root apical meristem (RAM) and cell elongation in the elongation zone. Much has been learned about the mechanisms that maintain the RAM, but how cell elongation is regulated is still unclear. Here we show that SCARECROW (SCR), a regulator of stem cell renewal and radial patterning in the Arabidopsis root, has a previously unrecognized role in promoting cell elongation. In further studies, we showed that the scr mutant has an elevated level of hydrogen peroxide, particularly in the elongation zone. When ABA signaling was blocked using the aba2 mutant, the scr root growth defects were largely rescued. Moreover, root length of the scr mutant was also significantly improved when cellular redox status was ameliorated by the upb1 mutant. Notably, the scr aba2 and scr upb1 double mutant roots had not only significantly longer cells but also a larger and mitotically more active apical meristem, although it still had the stem cell and radial patterning defects characteristic of scr. In the scr mutant, key peroxidase genes involved in Casparian strip formation were down regulated, whereas WRKY15, a ROS inducible gene and a direct SCR target, is upregulated. Together, these results suggest that SCR promotes root growth by suppressing the deleterious effects of oxidative stress as a result of endodermal cell specification.