Insight into the Salivary Gland Transcriptome of Lygus lineolaris (Palisot de Beauvois)

Abstract

The tarnished plant bug (TPB), Lygus lineolaris (Palisot de Beauvois) is a polyphagous, phytophagous insect that has emerged as a major pest of cotton, alfalfa, fruits, and vegetable crops in the eastern United States and Canada. Using its piercing-sucking mouthparts, TPB employs a “lacerate and flush” feeding strategy in which saliva injected into plant tissue degrades cell wall components and lyses cells whose contents are subsequently imbibed by the TPB. It is known that a major component of TPB saliva is the polygalacturonase enzymes that degrade the pectin in the cell walls. However, not much is known about the other components of the saliva of this important pest. In this study, we explored the salivary gland transcriptome of TPB using Illumina sequencing. After in silico conversion of RNA sequences into corresponding polypeptides, 25,767 putative proteins were discovered. Of these, 19,540 (78.83%) showed significant similarity to known proteins in the either the NCBI nr or Uniprot databases. Gene ontology (GO) terms were assigned to 7,512 proteins, and 791 proteins in the sialotranscriptome of TPB were found to collectively map to 107 Kyoto Encyclopedia of Genes and Genomes (KEGG) database pathways. A total of 3,653 Pfam domains were identified in 10,421 sialotranscriptome predicted proteins resulting in 12,814 Pfam annotations; some proteins had more than one Pfam domain. Functional annotation revealed a number of salivary gland proteins that potentially facilitate degradation of host plant tissues and mitigation of the host plant defense response. These transcripts/proteins and their potential roles in TPB establishment are described.

Identification of Genes Potentially Responsible for extra-Oral Digestion and Overcoming Plant Defense from Salivary Glands of the Tarnished Plant Bug (Hemiptera: Miridae) Using cDNA Sequencing

“…5 ). Our results are similar to the finding that six groups of PGs were present in L. lineolaris ( Showmaker et al 2016 ) and in A. lucorum ( Zhang et al 2015 ), suggesting that mirids may have a common trait in evolving diverse PG genes for adaptation to wide host ranges. In addition, we found that 26 coded PGs ( Table 5 ) from this study highly matched to the PGs of L .…”

“…Expression levels of these genes may be altered when TPBs feed on different host plants ( Habibi et al 2001 ). Our microarray data (data not shown) indicated 26 PG genes were significantly down-regulated in the TPBs collected from the horseweed ( Conyza canadensis ) than the TPBs fed on artificial diet, the same colony used by Showmaker et al (2016) . Other detoxification/adaptation related genes were significantly up-regulated.…”

“…The linkage of these genes needs to be clarified in future study. Therefore, our sample and gene profile in this study might be better for representing field populations of TPBs than the laboratory colony used by Showmaker et al (2016) .…”

Transcriptome analysis of the salivary glands of the grain aphid, Sitobion avenae

“…For investigating the roles of saliva in aphid–plant interactions, the composition of aphid salivary proteins first needs to be identified. Actually, the transcriptome of salivary glands has been analyzed in some hemipteran species such as potato leafhopper Empoasca fabae 23 , whitefly Bemisia tabaci 24 , rice brown planthopper Nilaparvata lugens 25 , green rice leafhopper Nephotettix cincticeps 26 , tarnished plant bug Lygus lineolaris 27 . Some salivary proteins with enzymatic activities were also identified in the watery saliva of M .…”

Functional analysis of two polygalacturonase genes in Apolygus lucorum associated with eliciting plant injury using RNA interference

“…The plant damage symptoms elicited by A. lucorum feeding are similar to those recorded after injection of salivary gland extraction (Zhang et al., ). PGs are the dominant salivary enzyme in several piercing–sucking insects, A. lucorum and several other (Allen & Mertens, ; Showmaker et al., ; Walker & Allen, ; Zhang et al., ). We note that a large number of PGs are present in these insects, making it difficult to identify specific roles of particular PGs in plant feeding.…”