RT Journal Article
SR Electronic
T1 A cell surface <em>O</em>-glycosylated peptide, AGP21, acts on the brassinosteroid pathway and modulates root hair cell fate
JF bioRxiv
FD Cold Spring Harbor Laboratory
SP 787143
DO 10.1101/787143
A1 Cecilia Borassi
A1 Javier Gloazzo Dorosz
A1 Martiniano M. Ricardi
A1 Laercio Pol Fachin
A1 Mariana Carignani Sardoy
A1 Eliana Marzol
A1 Silvina Mangano
A1 Diana Rosa Rodríguez Garcia
A1 Javier Martínez Pacheco
A1 Yossmayer del Carmen Rondón Guerrero
A1 Silvia M. Velasquez
A1 Bianca Villavicencio
A1 Marina Ciancia
A1 Georg Seifert
A1 Hugo Verli
A1 José M. Estevez
YR 2019
UL http://biorxiv.org/content/early/2019/10/02/787143.abstract
AB Root hairs (RHs) develop from specialized epidermal cells called trichoblasts, whereas epidermal cells that lack RHs are known as atrichoblasts. The mechanism controlling root epidermal cell fate is only partially understood. Root epidermis cell fate is regulated by a transcription factor complex that promotes the expression of the homeodomain protein GLABRA 2 (GL2), which blocks RH development by inhibiting ROOT HAIR DEFECTIVE 6 (RHD6). Suppression of GL2 expression activates RHD6, a series of downstream TFs including ROOT HAIR DEFECTIVE 6 LIKE-4 (RSL4 [Yi et al. 2010]) and their target genes, and causes epidermal cells to develop into RHs. Brassinosteroids (BRs) influence root epidermis cell fate. In the absence of BRs, phosphorylated BIN2 (a Type-II GSK3-like kinase) inhibits a protein complex that directly downregulates GL2 [Chen et al. 2014]. Here, we demonstrate that the genetic and pharmacological perturbation of the arabinogalactan protein (AGP) AGP21 in Arabidopsis thaliana, triggers aberrant RH development, similar to that observed in plants with defective BR signaling. We reveal that an O-glycosylated AGP21 peptide, which is positively regulated by BZR1, a transcription factor activated by BR signaling, affects RH cell fate by altering GL2 expression in a BIN2-dependent manner. These results indicate that perturbation of a cell surface AGP disrupts BR perception and inhibits the downstream effect of BIN2 on the RH repressor GL2 in root epidermal cells. In addition, AGP21 also acts in a BR-independent, AGP-dependent mode that together with BIN2 signalling cascade controls RH cell fate.HighlightsPerturbation of AGPs and the loss of AGP21 peptide trigger an abnormal RH cell fate.AGP21-mediated repression of GL2 expression activates the expression of RSL4 and EXP7 root hair proteins.AGP21 peptide acts in both a BR-dependent and BR-independent manner, with both pathways converging on a BIN2 downstream signalling cascade to controls GL2 expression.