Plant hormone interactions: innovative targets for crop breeding and management

Abstract

Here we highlight how both the root and shoot environment impact on whole plant hormone balance, particularly under stresses such as soil drying, and relate hormone ratios and relative abundances to processes influencing plant performance and yield under both mild and more severe stress. We discuss evidence (i) that abscisic acid (ABA) and ethylene act antagonistically on grain-filling rate amongst other yield-impacting processes; (ii) that ABA's effectiveness as an agent of stomatal closure can be modulated by coincident ethylene or cytokinin accumulation; and (iii) that enhanced cytokinin production can increase growth and yield by improving foliar stay-green indices under stress, and by improving processes that impact grain-filling and number, and that this can be the result of altered relative abundances of cytokinin and ABA (and other hormones). We describe evidence and novel processes whereby these phenomena are/could be amenable to manipulation through genetic and management routes, such that plant performance and yield can be improved. We explore the possibility that a range of ABA-ethylene and ABA-cytokinin relative abundances could represent targets for breeding/managing for yield resilience under a spectrum of stress levels between severe and mild, and could circumvent some of the pitfalls so far encountered in the massive research effort towards breeding for increases in the complex trait of yield.

Physiology and transcriptomics of water-deficit stress responses in wheat cultivars TAM 111 and TAM 112

“…Phytohormones have been shown to regulate stem carbon reserves, spike dry weight at anthesis, efficient carbon allocation, and partitioning between and among sink tissues to determine final grain yield (Dreccer et al, 2009;Fischer, 2011;Wilkinson et al, 2012). The differential accumulation of ABA in the flag leaves of TAM 112 and TAM 111 (Fig.…”

“…Recent studies have highlighted the importance of phytohormone balance and ABA homeostasis in gas exchange, resource mobilization and determination of grain number and eventual grain yield (Acharya and Assmann, 2009;Ji et al, 2011;Seiler et al, 2011;Sreenivasulu and Schnurbusch, 2012). The contribution of phytohormones in adaptation to WD stress makes the manipulation of their homeostasis and signaling promising breeding targets to improve yield, efficiency, and performance (Wilkinson et al, 2012). Further studies are required to elucidate the potential roles of phytohormones in determining grain yield and source-sink relationships under WD stress.…”

“…The key responses and core signaling components include photosynthetic byproducts such as sugars and reactive oxygen species (ROS), phytohormones, transcription factors, amino acids, and other metabolic signals (Gong et al, 2010;Lawlor, 2013;Pinheiro and Chaves, 2011). The phytohormone abscisic acid (ABA) has been proposed to regulate a reduction in photosynthesis and mediate photosynthate remobilization between source and sink tissues, while other hormones also play key roles (Pinheiro and Chaves, 2011;Wilkinson et al, 2012).…”

Interaction of aluminium and drought stress on root growth and crop yield on acid soils

“…Root-to-shoot signalling is often considered to be important in regulating shoot growth and water use when soil conditions change (Dodd 2005). Hormones such as ABA and cytokinins (CKs) have been implicated in the root-shoot signaling, either acting in isolation or concomitantly (Chaves and Oliveira 2004;Davies et al 2005;Schachtman and Goodger 2008;Wilkinson et al 2012). ABA has been identified as one of the major chemical signals involved in stomatal functioning by the regulation of longdistance transport and modulation of ABA concentration at the guard cells (Chaves et al 2003).…”

Stress-Induced Cytokinin Synthesis Increases Drought Tolerance through the Coordinated Regulation of Carbon and Nitrogen Assimilation in Rice

“…Plant hormones affect, either directly or indirectly, these pathways and can act antagonistically or synergistically when responding to environmental stress (Wilkinson et al, 2012). The exposure of plants to water-limiting conditions results in abscisic acid (ABA) synthesis that induces ABA-dependent gene expression (Yamaguchi-Shinozaki and Shinozaki, 2006), triggering the closure of stomata and reducing water loss during drought (Wilkinson and Davies, 2010).…”