Disrupting Buchnera aphidicola, the endosymbiotic bacteria of Myzus persicae, delays host plant acceptance

Abstract

Myzus persicae Sulzer, like almost all aphids, associates with the endosymbiotic bacterium, Buchnera aphidicola. Although the accepted function of B. aphidicola is to complete the aphid diet with nutrients such as essential amino acids and vitamins, there is evidence that the bacteria may participate in the plant-insect interaction. Moreover, bacterial proteins with potential effector action on the metabolism of the host plant have been identified in the saliva of M. persicae. However, the possible involvement of B. aphidicola in relation to host plant acceptance by aphids needs further investigation. The aim of this study was to evaluate the effect that the disruption of the B. aphidicola-M. persicae symbiosis has on aphid feeding behaviour and on the expression of aphid salivary genes. The antibiotic rifampicin was administrated to adult aphids through artificial diets to disrupt the bacterial primary endosymbionts. Comparisons were made with control aphids, feeding from diet without rifampicin, as well as normal aphids fed on radish plants. Differences were found in the feeding behaviour of aposymbiotic aphids, which had delayed host acceptance and problems during stylet penetration into host plants. It was also found that B. aphidicola disruption down-regulated the expression of the Mp63 salivary protein gene. Together, these results indicate that B. aphidicola plays a role in plant-aphid interactions. The validity of the use of artificial diets in plantaphid studies is also discussed.

Probing behavior of aposymbiotic green peach aphid (Myzus persicae) on susceptible Solanum tuberosum and resistant Solanum stoloniferum plants

“…Here, the increase in mechanical difficulties in stylet penetration is related to aposymbiosis and therefore the aposymbiotic aphids likely spent considerable more time in trying to restore the stylets bundle order than control aphids. We previously found F waveform in aposymbiotic aphids probing on radish plants; and the mechanical difficulties are presumably due to a deficient saliva composition (Machado‐Assefh et al ., ). The “F” variables of control aphids did not show differences between plant species (Table , variables 12–16); the incompatibility of control aphids with S. stoloniferum is then likely related to other factors than derailed stylet mechanics.…”

“…Another reason for the decreased E2 phloem ingestion here might be the aphids preceding artificial diet feeding, during which aphids have to actively ingest the diet because it lacks the high phloem sap pressure that enables the passive E2 ingestion. In our previous study of aposymbiotic aphids feeding behavior on radish (Machado‐Assefh et al ., ), the aphids that before the EPG experiment had been feeding on artificial diets spent significantly more time with active ingestion, drinking from xylem as compared to aphids from plants (these treatment was not included here).…”

“…after Prosser and Douglas (), and used in Machado‐Assefh et al . (). The insects were reared on radish until the first day of adulthood and then they were transferred to artificial diet cages, which consisted on a plastic cylinder of 3 cm height × 2 cm wide, with a mesh on the bottom and the top opened to allow respiration of the insects but preventing them from escaping.…”

“…To evaluate the efficiency of the antibiotic treatment the expression of a Buchnera ‐specific gene, GroEL, was measured by RT‐qPCR as in Machado‐Assefh et al . ().…”

“…We have recently demonstrated that in M. persicae , the disruption of the symbiosis with B. aphidicola negatively affected the feeding behavior on Raphanus sativus (which is a very suitable host for this aphid) causing a delay in host plant acceptance of this aphid. The aposymbiotic aphids also showed mechanical problems with stylet penetration into the plant tissues which likely was related to changes in aphid's saliva composition (Machado‐Assefh et al ., ). However, the involvement of B. aphidicola in relation to host‐plant acceptance by aphids needs further investigation to better understand the extent of the endosymbiont influence on plant–aphid interaction.…”