Extensive tissue-specific transcriptomic plasticity in maize primary roots upon water deficit.

Nina Opitz,Frank Hochholdinger,Andrew Lithio,Hans-Peter Piepho,Ronny Brandt,Waqas Ahmed Malik,Dan Nettleton,Caroline Marcon,Anja Paschold

doi:10.1093/jxb/erv453

Abstract

Water deficit is the most important environmental constraint severely limiting global crop growth and productivity. This study investigated early transcriptome changes in maize (Zea mays L.) primary root tissues in response to moderate water deficit conditions by RNA-Sequencing. Differential gene expression analyses revealed a high degree of plasticity of the water deficit response. The activity status of genes (active/inactive) was determined by a Bayesian hierarchical model. In total, 70% of expressed genes were constitutively active in all tissues. In contrast, <3% (50 genes) of water deficit-responsive genes (1915) were consistently regulated in all tissues, while >75% (1501 genes) were specifically regulated in a single root tissue. Water deficit-responsive genes were most numerous in the cortex of the mature root zone and in the elongation zone. The most prominent functional categories among differentially expressed genes in all tissues were 'transcriptional regulation' and 'hormone metabolism', indicating global reprogramming of cellular metabolism as an adaptation to water deficit. Additionally, the most significant transcriptomic changes in the root tip were associated with cell wall reorganization, leading to continued root growth despite water deficit conditions. This study provides insight into tissue-specific water deficit responses and will be a resource for future genetic analyses and breeding strategies to develop more drought-tolerant maize cultivars.

Highlights

In agriculture, drought is responsible for more yield losses than any other abiotic stress (Boyer, 1982)
This study investigated early transcriptome changes in maize (Zea mays L.) primary root tissues in response to moderate water deficit conditions by RNA-Sequencing
To survey the transcriptomic dynamics of maize root tissues in response to water deficit, seedlings were subjected to a low water potential of –0.8 MPa and control conditions for 6 h

Summary

Introduction

Drought is responsible for more yield losses than any other abiotic stress (Boyer, 1982). New insights into the molecular mechanisms of drought response and adaptation are required to advance. Root growth maintenance is an important adaptive trait ensuring that plants can access deep water and nutrient resources to survive (Rodrigues et al, 1995). It relies predominantly on the activity of the plant hormone abscisic acid (ABA). In spite of the well-known physiological processes, relatively little is known about the underlying gene regulatory networks that translate environmental changes to metabolic alterations needed to gain stress tolerance (Spollen et al, 2008; Krasensky and Jonak, 2012)

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