Immunoprofiling of Rice Root Cortex Reveals Two Cortical Subdomains.

Sophia Henry,Charlotte Bureau,Mathilde Bettembourg,Fanchon Divol,Christophe Périn,Anne Diévart,Emmanuel Guiderdoni

doi:10.3389/fpls.2015.01139

Abstract

The formation and differentiation of aerenchyma, i.e., air-containing cavities that are critical for flooding tolerance, take place exclusively in the cortex. The understanding of development and differentiation of the cortex is thus an important issue; however, studies on this tissue are limited, partly because of the lack of available molecular tools. We screened a commercially available library of cell wall antibodies to identify markers of cortical tissue in rice roots. Out of the 174 antibodies screened, eight were cortex-specific. Our analysis revealed that two types of cortical tissues are present in rice root seedlings. We named these cell layers “inner” and “outer” based on their location relative to the stele. We then used the antibodies to clarify cell identity in lateral roots. Without these markers, previous studies could not distinguish between the cortex and sclerenchyma in small lateral roots. By immunostaining lateral root sections, we showed that the internal ground tissue in small lateral roots has outer cortical identity.

Highlights

Rice has a complex root architecture with a mix of embryonic and post-embryonic roots
With the aim of identifying antibody-based markers for cortical cells, we first established a protocol for medium throughput immunolabeling of radial sections of fresh rice roots
Recent results suggest that this cortex layer, whose formation is regulated by GA, oxidative stress, and SHORT ROOT (SHR) and SCR among others, plays a role in abiotic tolerance (Paquette and Benfey, 2005; Cui and Benfey, 2009; Pauluzzi et al, 2012; Wu and Gallagher, 2014)

Summary

Introduction

Rice has a complex root architecture with a mix of embryonic and post-embryonic roots. The radicle emerges first during germination, followed soon thereafter by embryonic coronary roots (Rebouillat et al, 2009; Coudert et al, 2010). The first adventitious post-embryonic roots resulting from shoot apical meristem activity appear a few days after seedling germination. The internal rice root anatomy is well-described, at the seedling stages (Rebouillat et al, 2009). Several concentric tissues (from the periphery to the stele) are located between the epidermis and the vascular tissues (Figure 1). These tissues, collectively referred to as “ground tissue,” are sometimes referred to as the “cortex” (Lux et al, 2004). We refer to the “cortex” as the tissue located between the endodermis and the sclerenchyma

Methods

Results

Conclusion