Mapping and candidate gene identification of loci induced by phytohormones in barley (Hordeum vulgare L.)

E Tocho,U Lohwasser,A M Castro,A Börner

doi:10.1007/s10681-013-1003-2

Abstract

Phytohormones, a group of structurally unrelated small molecules are plant-signalling compounds that trigger induced resistance against certain pathogens and herbivores. The hormones jasmonic acid (JA), ABA, salicilic acid (SA) and ethylene (ET) are known to play major roles in regulating plant defence responses. In order to determine the changes in growth and in the chlorophyll content induced by the exogenous application of these elicitors, a set of DH lines of the Oregon-Wolfe Barley mapping population, previously screened to locate aphid resistant genes, was investigated. The aim of the current research was to map the induced defence genes and to reveal the relationship with aphid resistance. There were highly significant differences between controls and hormone treated plants in the aerial fresh and dry weights (AFW, ADW), the foliar area (FA) and the root dry weight (RDW). More than 15 JA and ET-induced lines exceeded the chlorophyll (Ch) values of their controls. Most of the plant traits were associated with the same genetic windows on chromosomes 3H, 5H and 7H in the controls and hormone treated plants. QTL(s) identified on chromosome 3H and 5H explained most of the variation of AFW, ADW, FA and RDW of controls and treated plants. QTL(s) located on chromosome 5H were associated with the variation of chlorophyll contents on JA-treated plants. The Ch in ET and ABA-treated plants was associated with two different regions on chromosome 7H. One of the latter genetic windows also explained the variation of RDW of ET- and ABA-treated plants. A sequence homology search was performed to derive the putative function of the genes linked to the QTLs. Several QTLs were identified located close to aphid resistance genes previously mapped. This is the first report of genes associated with hormone response in barley that could be involved with insect resistance. Those recombinant lines carrying the appropriate alleles could be useful for breeding barley to enlarge the genetic base of defence against stress.

Highlights

The plant hormones or phytohormones, a group of structurally unrelated small molecules, play important roles in diverse growth and developmental processes as well as various biotic and abiotic stress responses in plants (Santner et al 2009)
In the current study we identified QTLs distributed on chromosomes 3H, 5H and 7H with significant effects on the phenotypic variation of the responses to the hormone treatments in terms of AFW, ADW, foliar area (FA), Ch and root dry weight (RDW)
abscisic acid (ABA), ET, salicilic acid (SA) and jasmonic acid (JA) are signalling molecules for stress metabolism produced by plants under stress, and when exogenously applied, they induce a number of genes that respond to environmental or biotic stresses (Baldwin et al 1994; Soriano et al 2004; YamaguchiShinozaki and Shinozaki 2005; Yamaguchi-Shinozaki and Shinozaki 2006)

Summary

Introduction

The plant hormones or phytohormones, a group of structurally unrelated small molecules, play important roles in diverse growth and developmental processes as well as various biotic and abiotic stress responses in plants (Santner et al 2009). The jasmonic acid (JA), salicylic acid (SA), abscisic acid (ABA) and ethylene (ET) are known to play major roles in regulating plant defence responses against various pathogens, pests and abiotic stresses, wounding and exposure to ozone (Glazebrook 2005). These phytohormone signalling pathways are complex, often interacting antagonistically or synergistically with each other to allow the plant to fine-tune and activate attacker-specific responses (Bari and Jones 2009). The role of SA in response to aphid feeding has been observed in many plant species such as wheat, barley and Arabidopsis thaliana. Activation of the SA pathway may be a general mechanism of antibiosis or aphid repellence in resistant hosts, with a limited effectiveness in susceptible ones

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