The molecular bases of plant resistance and defense responses to aphid feeding: current status

Abstract

Plant genes participating in the recognition of aphid herbivory in concert with plant genes involved in defense against herbivores mediate plant resistance to aphids. Several such genes involved in plant disease and nematode resistance have been characterized in detail, but their existence has only recently begun to be determined for arthropod resistance. Hundreds of different genes are typically involved and the disruption of plant cell wall tissues during aphid feeding has been shown to induce defense responses in Arabidopsis , Triticum , Sorghum , and Nicotiana species . Mi-1.2 , a tomato gene for resistance to the potato aphid, Macrosiphum euphorbiae (Thomas), is a member of the nucleotidebinding site and leucine-rich region Class II family of disease, nematode, and arthropod resistance genes. Recent studies into the differential expression of Pto -and Pti1 -like kinase genes in wheat plants resistant to the Russian wheat aphid, Diuraphis noxia (Mordvilko), provide evidence of the involvement of the Pto class of resistance genes in arthropod resistance. An analysis of available data suggests that aphid feeding may trigger multiple signaling pathways in plants. Early signaling includes gene-for-gene recognition and defense signaling in aphid-resistant plants, and recognition of aphidinflicted cell damage in both resistant and susceptible plants. Furthermore, signaling is mediated by several compounds, including jasmonic acid, salicylic acid, ethylene, abscisic acid, giberellic acid, nitric oxide, and auxin. These signals lead to the development of direct chemical defenses against aphids and general stress-related responses that are well characterized for a number of abiotic and biotic stresses. In spite of major plant taxonomic differences, similarities exist in the types of plant genes expressed in response to feeding by different species of aphids. However, numerous differences in plant signaling and defense responses unique to specific aphid-plant interactions have been identified and warrant further investigation.

Transcriptomics of induced defense responses to greenbug aphid feeding in near isogenic wheat lines

“…From a plant breeding perspective, R gene-mediated host defenses play critical roles against herbivore damage; however, the detailed physiological and molecular basis of gene-for-gene interactions in the grass genomes like wheat remains unclear [33,34]. Host resistance to piercing/sucking insects is usually controlled by single or major genes [35].…”

Transcriptional responses of tolerant and susceptible soybeans to soybean aphid (Aphis glycines Matsumura) herbivory

“…Plant tolerance is a form of resistance that allows a plant to harbor a large number of aphids without a significant loss in yield (Smith 2005). Although tolerance has been identified in soybean (Pierson et al 2010;Prochaska et al 2013), limited information is available on how soybean aphid feeding impacts the underlying transcriptional machinery of the plant.…”

Aphid acceptance of Hordeum genotypes is affected by plant volatile exposure and is correlated with aphid growth

“…The finding aphid host relations can be affected by volatile induction from undamaged and damaged plants led us to question whether this might affect the outcome of aphid resistance tests for plant breeding. When screening for resistance to pests and diseases for the purpose of selecting resistant plant genotypes, the common procedure is to grow different genotypes in greenhouses or climate chambers within a restricted area, in order to compare plants under similar environmental conditions (Smith 1989). This arrangement will, however, facilitate transfer of plant volatiles between plant individuals, introducing a further potential source of variation in the results.…”

“…Alternatively, poor aphid growth can be a result of poor food quality due to plant toxins or an imbalanced nutrient composition. Thus, when determination of plant resistance is based on aphid growth measurements alone it is not obvious whether antixenosis, insect behavioural responses to host resistance characteristics, or antibiosis, insect physiological responses, are causing the resistance (Smith 1989). …”