Ethylene response factor ERF022 is involved in regulating Arabidopsis root growth

Ethylene response factors (ERFs) are involved in the regulation of plant development processes and stress responses. In this study, we provide evidence for the role of ERF022, a member of the ERF transcription factor group III, in regulating Arabidopsis root growth. We found that ERF022-loss-of-function mutants exhibited increased primary root length and lateral root numbers, and also morphological growth advantages compared to wild-type. Further studies showed that mutants had enhanced cell size in length in the root elongation zones. These results were accompanied by significant increase in the expression of cell elongation and cell wall expansion related genes SAUR10, GASA14, LRX2, XTH19 in mutants. Moreover, ERF022-mediated root growth was associated with the enhanced endogenous auxin and gibberellins levels. Our results suggest that loss-of-function of ERF022 up-regulated the expression of cell elongation and cell wall related genes through auxin and gibberellins signal in the regulation of root growth. Unexpectedly, ERF022 overexpression lines also showed longer primary roots and more lateral roots compared to wild-type, and had longer root apical meristematic zone with increased cell numbers. Overexpression of ERF022 significantly up-regulated cell proliferation, organ growth and auxin biosynthesis genes EXO, HB2, GALK2, LBD26, YUC5, which contribute to enhanced root growth. Altogether, our results provide genetic evidence that ERF022 plays an important role in regulating root growth in Arabidopsis thaliana.