Abstract
Aphids secrete proteins from their stylets that evidence indicates function similar to pathogen effectors for virulence. Here, we describe two small candidate effector gene families of the pea aphid, Acyrthosiphon pisum, that share highly conserved secretory signal peptide coding regions and divergent non-secretory coding sequences derived from miniature exons. The KQY candidate effector family contains eleven members with additional isoforms, generated by alternative splicing. Pairwise comparisons indicate possible four unique KQY families based on coding regions without the secretory signal region. KQY1a, a representative of the family, is encoded by a 968 bp mRNA and a gene that spans 45.7 kbp of the genome. The locus consists of 37 exons, 33 of which are 15 bp or smaller. Additional KQY members, as well as members of the KHI family, share similar features. Differential expression analyses indicate that the genes are expressed preferentially in salivary glands. Proteomic analysis on salivary glands and saliva revealed 11 KQY members in salivary proteins, and KQY1a was detected in an artificial diet solution after aphid feeding. A single KQY locus and two KHI loci were identified in Myzus persicae, the peach aphid. Of the genes that can be anchored to chromosomes, loci are mostly scattered throughout the genome, except a two-gene region (KQY4/KQY6). We propose that the KQY family expanded in A. pisum through combinatorial assemblies of a common secretory signal cassette and novel coding regions, followed by classical gene duplication and divergence.
Highlights
Aphids are important pests of plants that can cause economical damage through loss of crop yield and dissemination of plant viruses through their feeding habits (Miles, 1999)
Sequenced salivary gland cDNA sequences for A. pisum were retrieved from NCBI, and dataset was analyzed for sequences encoding predicted secreted peptides
We add to the characterization of candidate effectors of A. pisum, and, by sequence relatedness, possibly, M. persicae with the description of two families of genes, which by several criteria, appear to be variable secreted salivary gland proteins (Carolan et al, 2009; Carolan et al, 2011; Rao et al, 2013; Boulain et al, 2018)
Summary
Aphids are important pests of plants that can cause economical damage through loss of crop yield and dissemination of plant viruses through their feeding habits (Miles, 1999). Pea Aphid Cassette Effector Families from narrow to broad (Jaouannet et al, 2014). An aphid with a broad host range can feed on many different plant species spanning different taxonomic families. During this interaction, aphids extract phloem sap from the leaves and stems of the host plant through stylets, which are inserted into phloem cells. Aphids extract phloem sap from the leaves and stems of the host plant through stylets, which are inserted into phloem cells Plants possess both a constitutive and inducible immune response that fights insect consumption (Cook et al, 2015). Aphid interactions with non-host plants are hypothesized to fail, in part, due to an immune reaction, while a successful aphid feeding involves suppressing the plant immune response (Jaouannet et al, 2014)
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