The involvement of J-protein AtDjC17 in root development in Arabidopsis.

Carloalberto Petti,Meera Nair,Seth Debolt

doi:10.3389/fpls.2014.00532

Abstract

In a screen for root hair morphogenesis mutants in Arabidopsis thaliana L. we identified a T-DNA insertion within a type III J-protein AtDjC17 caused altered root hair development and reduced hair length. Root hairs were observed to develop from trichoblast and atrichoblast cell files in both Atdjc17 and 35S::AtDJC17. Localization of gene expression in the root using transgenic plants expressing proAtDjC17::GUS revealed constitutive expression in stele cells. No AtDJC17 expression was observed in epidermal, endodermal, or cortical layers. To explore the contrast between gene expression in the stele and epidermal phenotype, hand cut transverse sections of Atdjc17 roots were examined showing that the endodermal and cortical cell layers displayed increased anticlinal cell divisions. Aberrant cortical cell division in Atdjc17 is proposed as causal in ectopic root hair formation via the positional cue requirement that exists between cortical and epidermal cell in hair cell fate determination. Results indicate a requirement for AtDJC17 in position-dependent cell fate determination and illustrate an intriguing requirement for molecular co-chaperone activity during root development.

Highlights

MUTATIONS IN Atdjc17 CAUSED ALTERED ORGANIZATION OF ROOT HAIR POSITION IN ATRICHOBLAST VERSUS TRICHOBLAST CELL FILES In a screen for altered root hair (H-cell) occurrence, we identified a causal mutation in Atdjc17-1-1 (At5g23240)
Mutations in AtDjC17 identified in this study, caused aberrant cell fate determination and cell divisions in ground tissue layers in Arabidopsis roots
Existing literature supports DNAJ/J-domain family proteins functioning as co-chaperones working in association with HSP70 class proteins (Miernyk, 2001; Qiu et al, 2006; Summers et al, 2009; Jelenska et al, 2010; Bekh-Ochir et al, 2013) and based on the observed root phenotypes, we hypothesized that AtDjC17 would plausibly be required for cell fate determination by acting in a client:binary complex with a cognate HSP70 as a protein chaperone to fortify key stage(s) in the pathway

Summary

Introduction

Atrichoblast cells or non-root hairs (N) relies on positional information, whereby epidermal cells in direct contact with anticlinal cell walls of two underlying cortical cells acquire H cell fate and all others become N cells (Dolan et al, 1994; Dolan, 2006). This position-dependent cell fate determination at the root epidermis is reliant on a complex regulatory pathway involving genetic cell fate determinants and mobile transcriptional regulators (Kwak et al, 2005; Kwak and Schiefelbein, 2007). The combined effect of these factors causes activation of direct targets including the N-cell determinant and homeodomain-leucine-zipper transcription factor GLABRA2 (GL2; Kwak and Schiefelbein, 2008)

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