Comparison of Potato and Asian Citrus Psyllid Adult and Nymph Transcriptomes Identified Vector Transcripts with Potential Involvement in Circulative, Propagative Liberibacter Transmission

Tonja Fisher,Ryan Kim,Mark Willer,David Gang,Carol Soderlund,Ruifeng He,Judith Brown,William Nelson,John Crow,Joseph Cicero,Meenal Vyas,Greg May,Robin Kramer

doi:10.3390/pathogens3040875

Tonja Fisher, Ryan Kim + Show 11 more

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https://doi.org/10.3390/pathogens3040875

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Abstract

The potato psyllid (PoP) Bactericera cockerelli (Sulc) and Asian citrus psyllid (ACP) Diaphorina citri Kuwayama are the insect vectors of the fastidious plant pathogen, Candidatus Liberibacter solanacearum (CLso) and Ca. L. asiaticus (CLas), respectively. CLso causes Zebra chip disease of potato and vein-greening in solanaceous species, whereas, CLas causes citrus greening disease. The reliance on insecticides for vector management to reduce pathogen transmission has increased interest in alternative approaches, including RNA interference to abate expression of genes essential for psyllid-mediated Ca. Liberibacter transmission. To identify genes with significantly altered expression at different life stages and conditions of CLso/CLas infection, cDNA libraries were constructed for CLso-infected and -uninfected PoP adults and nymphal instars. Illumina sequencing produced 199,081,451 reads that were assembled into 82,224 unique transcripts. PoP and the analogous transcripts from ACP adult and nymphs reported elsewhere were annotated, organized into functional gene groups using the Gene Ontology classification system, and analyzed for differential in silico expression. Expression profiles revealed vector life stage differences and differential gene expression associated with Liberibacter infection of the psyllid host, including invasion, immune system modulation, nutrition, and development.

Highlights

The potato/tomato psyllid (PoP), Bactericera cockerelli (Sulc) (Triozidae) is a hemipteran insect that colonizes mainly plant species in Convolvulaceae and Solanaceae
Analyzer IIx platform (Illumina, San Diego, CA, USA) to generate 2 × 54 bp independent reads from either end of a 250 ± 25 bp insert library fragment, resulting in a total of 199,081,451 clean reads, including 46,681,564 reads from library Wb, 53,240,863 reads from library WbL, 43,322,502 reads from library Ny and 55,836,522 reads from library NyL (Supplementary Table S1)
The grid was air-dried for several hours and examined using a Phillips CM-12 transmission electron microscope operated at 80 kV. This manuscript highlights the results of an interdisciplinary research effort that has produced the first annotated, differentially expressed transcriptomes of adult and nymphal stage potato psyllid (PoP) either free of or harboring Candidatus Liberibacter solanacearum (CLso)

Summary

Introduction

The potato/tomato psyllid (PoP), Bactericera cockerelli (Sulc) (Triozidae) is a hemipteran insect that colonizes mainly plant species in Convolvulaceae and Solanaceae. PoP transmits a recently discovered, fastidious bacterium that has been associated with the emergence of the plant diseases, zebra chip of potato (affecting leaves and tubers) and vein greening of tomato (affecting leaves and fruit) and other solanaceous species [1,2,3]. The potato psyllid was known only for its association with “psyllid yellows” disease of tomato, pepper, and potato plants, syndromes attributed to psyllid feeding alone and to a salivary toxin [6]. These observations strongly suggest that CLso emergence and PoP transmission of it is a recent phenomenon. HLB has reached a crisislevel in the citrus industry worldwide [9]

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