Barley transcriptome analyses upon interaction with different aphid species identify thionins contributing to resistance.

C.M Escudero‐Martinez,P.E Hedley,J.I.B Bos,J.A Morris

doi:10.1111/pce.12979

Abstract

Aphids are phloem‐feeding insects that cause yield loss on a wide range of crops, including cereals such as barley. Whilst most aphid species are limited to one or few host species, some are able to reproduce on many plants belonging to different families. Interestingly, aphid probing behaviour can be observed on both host and non‐host species, indicating that interactions take place at the molecular level that may impact host range. Here, we aimed to gain insight into the interaction of barley with aphid species differing in their ability to infest this crop by analysing transcriptional responses. Firstly, we determined colonization efficiency, settlement and probing behaviour for the aphid species Rhopalosiphum padi, Myzus persicae and Myzus cerasi, which defined host, poor‐host and non‐host interactions, respectively. Analyses of barley transcriptional responses revealed gene sets differentially regulated upon the different barley–aphid interactions and showed that the poor‐host interaction with M. persicae resulted in the strongest regulation of genes. Interestingly, we identified several thionin genes strongly up‐regulated upon interaction with M. persicae, and to a lesser extent upon R. padi interaction. Ectopic expression of two of these genes in Nicotiana benthamiana reduced host susceptibility to M. persicae, indicating that thionins contribute to defences against aphids.

Highlights

Aphids are phloem-feeding insects that cause substantial yield loss on a wide range crop plants, including monocots and dicots
Our work provides insights into how barley responds to different types of aphid interactions
Aphid probingbehaviour can be observed on both host and non-host species indicating that interactions take place at the molecular level that may impact host range

Summary

Introduction

Aphids are phloem-feeding insects that cause substantial yield loss on a wide range crop plants, including monocots and dicots. Most aphid species have a narrow host range, limited to one or few plant families. Some aphids are able to infest a wide range of plant species, including many important agricultural crops. One example is Myzus persicae (green peach aphid), which can infest plants in over 40 families, including solanaceous crops such as potato and tomato, cucurbits, legumes, as well as ornamentals (Blackman and Eastop, 2000). Closely related Myzus cerasi (black cherry aphid) is only able to infest a small number of herbaceous plants. Host selection by aphids involves a complex set of plant cues and signals, and most likely, molecular interactions that take place between plant and aphid upon probing and feeding (as reviewed by Powell et al, 2006; Jaouannet et al, 2013)

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