Identification of Candidate Transcriptional Regulators of Epidermal Transfer Cell Development in Vicia faba Cotyledons.

Kiruba S Arun-Chinnappa,David W Mccurdy

doi:10.3389/fpls.2016.00717

Kiruba S Arun-Chinnappa, David W Mccurdy

Open Access

https://doi.org/10.3389/fpls.2016.00717

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Abstract

Transfer cells (TCs) are anatomically-specialized cells formed at apoplasmic-symplasmic bottlenecks in nutrient transport pathways in plants. TCs form invaginated wall ingrowths which provide a scaffold to amplify plasma membrane surface area and thus increase the density of nutrient transporters required to achieve enhanced nutrient flow across these bottlenecks. Despite their importance to nutrient transport in plants, little is known of the transcriptional regulation of wall ingrowth formation. Here, we used RNA-Seq to identify transcription factors putatively involved in regulating epidermal TC development in cotyledons of Vicia faba. Comparing cotyledons cultured for 0, 3, 9, and 24 h to induce trans-differentiation of epidermal TCs identified 43 transcription factors that showed either epidermal-specific or epidermal–enhanced expression, and 10 that showed epidermal-specific down regulation. Members of the WRKY and ethylene-responsive families were prominent in the cohort of transcription factors showing epidermal-specific or epidermal–enhanced expression, consistent with the initiation of TC development often representing a response to stress. Members of the MYB family were also prominent in these categories, including orthologs of MYB genes involved in localized secondary wall deposition in Arabidopsis thaliana. Among the group of transcription factors showing down regulation were various homeobox genes and members of the MADs-box and zinc-finger families of poorly defined functions. Collectively, this study identified several transcription factors showing expression characteristics and orthologous functions that indicate likely participation in transcriptional regulation of epidermal TC development in V. faba cotyledons.

Highlights

Transfer cells (TCs) commonly trans-differentiate from various differentiated cell types at anatomical locations where enhanced rates of nutrient transport are required for programmed development or in response to stress (Offler et al, 2003)
In this study we used RNA-Seq to identify transcription factors putatively regulating the trans-differentiation of epidermal TCs in cultured V. faba cotyledons
Culturing V. faba cotyledons induces adaxial epidermal cells to form TCs, but cells of the neighboring storage parenchyma tissue do not, offering an experimental system to identify signaling pathways inducing epidermal TC trans-differentiation (Zhou et al, 2010; Andriunas et al, 2011, 2012) as well as global gene expression events associated with this process (Dibley et al, 2009; Zhang et al, 2015b)

Summary

Introduction

Transfer cells (TCs) commonly trans-differentiate from various differentiated cell types at anatomical locations where enhanced rates of nutrient transport are required for programmed development or in response to stress (Offler et al, 2003). Transcript profiling in endosperm TCs of barley (Thiel et al, 2008, 2012) and epidermal TCs of Vicia faba cotyledons (Dibley et al, 2009; Zhang et al, 2015b) established that wall ingrowth deposition involves differential expression of many hundreds of genes, presumably organized within transcriptional cascades to coordinate expression of the biosynthetic machinery required for wall ingrowth deposition and TC function (Arun-Chinnappa et al, 2013) These studies identified a role for auxin and ethylene signaling in inducing TC development, and details of the involvement of epidermal-specific ethylene and reactive oxygen species signaling pathways in epidermal TC induction have been elucidated (Zhou et al, 2010; Andriunas et al, 2011, 2012).

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