Overexpression and Down-Regulation of Barley Lipoxygenase LOX2.2 Affects Jasmonate-Regulated Genes and Aphid Fecundity

Aleksandra Losvik,Jennifer Stephens,Robert Glinwood,Emelie Ivarson,Lisbeth Jonsson,Lisa Beste,Li-Hua Zhu

doi:10.3390/ijms18122765

Abstract

Aphids are pests on many crops and depend on plant phloem sap as their food source. In an attempt to find factors improving plant resistance against aphids, we studied the effects of overexpression and down-regulation of the lipoxygenase gene LOX2.2 in barley (Hordeum vulgare L.) on the performance of two aphid species. A specialist, bird cherry-oat aphid (Rhopalosiphum padi L.) and a generalist, green peach aphid (Myzus persicae Sulzer) were studied. LOX2.2 overexpressing lines showed up-regulation of some other jasmonic acid (JA)-regulated genes, and antisense lines showed down-regulation of such genes. Overexpression or suppression of LOX2.2 did not affect aphid settling or the life span on the plants, but in short term fecundity tests, overexpressing plants supported lower aphid numbers and antisense plants higher aphid numbers. The amounts and composition of released volatile organic compounds did not differ between control and LOX2.2 overexpressing lines. Up-regulation of genes was similar for both aphid species. The results suggest that LOX2.2 plays a role in the activation of JA-mediated responses and indicates the involvement of LOX2.2 in basic defense responses.

Highlights

Many crop species suffer considerable damage due to infestation by aphids
Attempts to breed for aphid resistance have not produced any commercial barley cultivar resistant to Bird cherry-oat aphid (BCA); they have resulted in a number of doubled haploid breeding lines with moderate resistance to this aphid species [6,7]
Four other genes known to be regulated by jasmonic acid (JA) showed a significantly higher transcript abundance in the overexpressing plants compared to the control plants: LOX2.1 (p < 0.0001), AOS1 (p < 0.05), LOX1 (p < 0.0001), and CI2c (p < 0.01) (Figure 1)

Summary

Introduction

Many crop species suffer considerable damage due to infestation by aphids. They cause little wounding injury to the plant tissue, they can induce stunting, chlorosis, necrosis, or plant deformation [1,2]. Bird cherry-oat aphid (BCA; Rhopalosiphum padi L.) is a common pest on cereals, including barley and wheat. It does not cause visible injury, it is a vector for barley yellow dwarf virus, which causes symptoms such as leaf discoloration and dwarfing [3,4,5].

Results

Discussion

Conclusion