No abstract

Potato leafroll virus (PLRV), genus Polerovirus, family Luteoviridae, is a major pathogen of potato worldwide. PLRV is transmitted among host plants by aphids in a circulative–nonpropagative manner. Previous studies have demonstrated that PLRV infection increases aphid fecundity on, and attraction to, infected plants as compared to controls. However, the molecular mechanisms mediating this relationship are still poorly understood. In this study, we measured the impact of PLRV infection on plant–aphid interactions and plant chemistry in two hosts: Solanum tuberosum and Nicotiana benthamiana. Our study demonstrates that PLRV infection attenuates the induction of aphid‐induced jasmonic acid and ethylene in S. tuberosum and N. benthamiana. Using transient expression experiments, insect bioassays and chemical analysis, we show that expression of three PLRV proteins (P0, P1, and P7) mediate changes in plant–aphid interactions and inhibition of aphid‐induced jasmonic acid and ethylene in N. benthamiana. This study enhances our understanding of the plant‐vector‐pathogen interface by elucidating new mechanisms by which plant viruses transmitted in a circulative manner can manipulate plant hosts.

Viruses in the Luteoviridae family, such as Potato leafroll virus (PLRV), are transmitted by aphids in a circulative and nonpropagative mode. This means the virions enter the aphid body through the gut when they feed from infected plants and then the virions circulate through the hemolymph to enter the salivary glands before being released into the saliva. Although these viruses do not replicate in their insect vectors, previous studies have demonstrated viruliferous aphid behavior is altered and the obligate symbiont of aphids, Buchnera aphidocola, may be involved in transmission. Here we provide the transcriptome of green peach aphids (Myzus persicae) carrying PLRV and virus-free control aphids using Illumina sequencing. Over 150 million paired-end reads were obtained through Illumina sequencing, with an average of 19 million reads per library. The comparative analysis identified 134 differentially expressed genes (DEGs) between the M. persicae transcriptomes, including 64 and 70 genes that were up- and down-regulated in aphids carrying PLRV, respectively. Using functional classification in the GO databases, 80 of the DEGs were assigned to 391 functional subcategories at category level 2. The most highly up-regulated genes in aphids carrying PLRV were cytochrome p450s, genes related to cuticle production, and genes related to development, while genes related to heat shock proteins, histones, and histone modification were the most down-regulated. PLRV aphids had reduced Buchnera titer and lower abundance of several Buchnera transcripts related to stress responses and metabolism. These results suggest carrying PLRV may reduce both aphid and Buchnera genes in response to stress. This work provides valuable basis for further investigation into the complicated mechanisms of circulative and nonpropagative transmission.

Plants utilise diverse defences to deter herbivore feeding. In response, insect herbivores have evolved an equally impressive array of strategies to counter plant defences and promote successful nutrient acquisition. Cardiaspina psyllids induce premature senescence in eucalypt leaves, increasing the nutritional value of the plant for the insect. Interestingly, eucalypt leaves colonised by another group of psyllids, Glycaspis, do not exhibit any observable symptoms of premature senescence, suggesting that different mechanisms are at work. The aim of this study was to investigate the transcriptional and polyphenolic profiles of Eucalyptus camaldulensis (river red gum) leaves in response to feeding by Glycaspis brimblecombei. We used RNA sequencing to evaluate the global gene expression of E. camaldulensis leaves after Glycaspis immature feeding compared with uninfested leaves. Polyphenolic profiles were investigated by using liquid chromatography coupled to mass spectrometry from the same leaf material. We observed that 413 transcripts were differentially expressed between uninfested and infested leaves. There were few changes in polyphenol profiles among treatments, although psyllid feeding increased quercetin glucoside and pentagalloylglucose content. Overall, the analysis reveals that E. camaldulensis responses to Glycaspis immatures involve several potential mechanisms, including changes in defence responses, signal transduction and plant redox status. Candidate genes identified in this study can be examined in future experiments to understand their role in eucalypt–psyllid interactions.