Genome duplication improves rice root resistance to salt stress.

Yi Tu,Jinming Zhang,Yuguo Xiong,Bo Peng,Aiming Jiang,Jianhua Zhang,Zhaojian Song,Yuchi He,Detian Cai,Lu Gan,Weifeng Xu,Mokter Hossain

doi:10.1186/s12284-014-0015-4

Abstract

BackgroundSalinity is a stressful environmental factor that limits the productivity of crop plants, and roots form the major interface between plants and various abiotic stresses. Rice is a salt-sensitive crop and its polyploid shows advantages in terms of stress resistance. The objective of this study was to investigate the effects of genome duplication on rice root resistance to salt stress.ResultsBoth diploid rice (HN2026-2x and Nipponbare-2x) and their corresponding tetraploid rice (HN2026-4x and Nipponbare-4x) were cultured in half-strength Murashige and Skoog medium with 150 mM NaCl for 3 and 5 days. Accumulations of proline, soluble sugar, malondialdehyde (MDA), Na+ content, H+ (proton) flux at root tips, and the microstructure and ultrastructure in rice roots were examined. We found that tetraploid rice showed less root growth inhibition, accumulated higher proline content and lower MDA content, and exhibited a higher frequency of normal epidermal cells than diploid rice. In addition, a protective gap appeared between the cortex and pericycle cells in tetraploid rice. Next, ultrastructural analysis showed that genome duplication improved membrane, organelle, and nuclei stability. Furthermore, Na+ in tetraploid rice roots significantly decreased while root tip H+ efflux in tetraploid rice significantly increased.ConclusionsOur results suggest that genome duplication improves root resistance to salt stress, and that enhanced proton transport to the root surface may play a role in reducing Na+ entrance into the roots.

Highlights

Salinity is a stressful environmental factor that limits the productivity of crop plants, and roots form the major interface between plants and various abiotic stresses
Our results demonstrated that salt stress significantly restricted rice root growth, irrespective of being diploid or tetraploid rice, and genome duplication improved root resistance in tetraploid rice by contributing to faster and better root growth in the presence of 150 mM NaCl (Figure 1)
Our results demonstrated that salt stress significantly restricted rice root growth in both diploid and tetraploid rice, and that genome duplication improved the root growth in tetraploid rice, with faster and better root growth in the presence of 150 mM NaCl

Summary

Introduction

Salinity is a stressful environmental factor that limits the productivity of crop plants, and roots form the major interface between plants and various abiotic stresses. The mechanisms by which Na+ enters the shoots of plants remain unclear (Kronzucker and Britto 2011), but apoplastic transpirational bypass flow of water and solutes is known to play an important role in rice (Yeo et al 1987; Ochiai and Matoh 2002). The majority of Na+ that enters the shoots of rice plants occurs through “apoplastic bypass,” whereby Na+ ions move through the apoplast via solvent drag (Ranathunge et al 2005), bypassing Casparian bands (Ochiai and Matoh 2002; Gong et al 2006). The highly suberized endodermal barrier presents the major resistance to radial water flow (Miyamoto et al 2001; Ranathunge et al 2003). The chemical composition of suberin in the apoplastic barrier affects the hydraulic conductivity of roots (Schreiber et al 2005)

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