Cell fate switch in response to impaired ribosome biogenesis ($) (Plant Cell)

Root hairs are epidermal projections that help plants to absorb water and nutrients from the soil. Root hair development is initiated by the cumulative action of TRANSPARENT TESTA GLABRA1 (TTG1, a WD40 domain protein), GLABRA3/ENHANCER OF GLABRA3 (GL3/EGL3, a bHLH), CAPRICE (CPC, a MYB), inhibited by the same set of proteins except that CPC is replaced by other MYB protein(s) called WEREWOLF (WER) and MYB23. In the cpc mutant, the root hair production is reduced because of more ectopic non-hair cell formation, but not abolished completely, raising a question of redundancy. In this paper, Wang et al. have identified a redundant root hair development pathway initiated in response to the impaired ribosome biogenesis. In an enhancer screen of the cpc mutant, the authors identified ARABIDOPSIS PUMILIO23 (APUM23), which encodes a ribosome biogenesis factor (RBF) and positively regulates the root hair development. Using molecular genetic experiments, authors found that apum23 shows an ectopic expression of MYB23, mediated by ANAC082 (encoding a NAC family transcription factor). Also, the authors identified ectopic non-hair cell formation in other RBF mutants and in response to flaellin22, suggesting that epidermal cell fate switch is a general response to RBF deficiency and few biotic stresses. Thus, this paper advances our understanding of cell fate switch between root hair and non-hair cells in responses to various stress conditions by activating ANAC082 and MYB23 pathway. (Summary by Vijaya Batthula @Vijaya_Batthula) The Plant Cell 10.1105/tpc.19.00773