Assessment of Local and Systemic Changes in Plant Gene Expression and Aphid Responses during Potato Interactions with Arbuscular Mycorrhizal Fungi and Potato Aphids.

Eric Rizzo,Tyler Sherman,S. Karen Gomez,Patricia Manosalva

doi:10.3390/plants9010082

Abstract

This research examined aphid and plant responses to distinct levels (none, low, and high) of arbuscular mycorrhizal (AM) fungal root colonization by studying the association between potato aphids (Macrosiphum euphorbiae), potatoes (Solanum tuberosum), and AM fungi (Rhizophagus intraradices). It extends knowledge on gene expression changes, assessed by RT–qPCR, of ten defense-related genes at two time-points post-herbivory (24 h and 10 days), focusing on aphid-infested local leaves, non-infested systemic leaves, and roots. The results showed that aphid fitness was not altered by AM symbiosis. At 24 h, ETHYLENE RECEPTOR 1 gene expression was repressed in roots of aphid-infested non-mycorrhizal plants and aphid-infested plants with a high level of AM fungal root colonization, but not on aphid-infested plants with a low level of AM fungal root colonization. At 10 days, ALLENE OXIDE CYCLASE and POTATO TYPE I PROTEASE INHIBITOR were upregulated exclusively in local leaves of aphid-infested plants with a low level of AM fungal root colonization. In addition, local and systemic changes in plant gene expression appeared to be regulated exclusively by AM status and aphid herbivory. In summary, the gene expression data provide insights on mycorrhizal potato responses to aphid herbivory and serve as a starting point for future studies using this system.

Highlights

Arbuscular mycorrhizal (AM) fungi are mostly known for aiding plants with the uptake of soil nutrients, such as phosphorus [1,2], and for helping plants better cope with abiotic [2,3,4,5] and biotic [2,6,7,8,9,10,11] stress
A study that included more than one level of AM fungal root colonization found that pea aphids (Acyrthosiphon pisum Harris) grew faster if broad bean (Vicia faba L.) plants were already colonized by AM fungi (40%–60% root length colonized (RLC)) at the beginning of aphid feeding, compared with insects on non-mycorrhizal plants [27]
The reduction in the relative growth rate of the green peach aphid (Myzus persicae Sulzer) was observed when insects fed on young Plantago lanceolata L. plants with low levels of AM fungal root colonization (10% RLC), whereas aphids benefited when feeding on older plants with high levels of AM fungal root colonization

Summary

Introduction

Arbuscular mycorrhizal (AM) fungi are mostly known for aiding plants with the uptake of soil nutrients, such as phosphorus [1,2], and for helping plants better cope with abiotic [2,3,4,5] and biotic [2,6,7,8,9,10,11] stress Another aspect of this ubiquitous symbiosis that is intriguing involves the impact of AM fungi on plant immunity, especially against aboveground and belowground insect herbivores [12,13,14].

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