Insect Science (2017) 24, 431–442, DOI 10.1111/1744-7917.12336 ORIGINAL ARTICLE Large-scale gene expression reveals different adaptations of Hyalopterus persikonus to winter and summer host plants Na Cui1,4,∗, Peng-Cheng Yang2,∗, Kun Guo1,3, Le Kang1,4 and Feng Cui1 1State Key Laboratory of Integrated Management of Pest Insects & Rodents, Institute of Zoology, Chinese Academy of Sciences, Beijing 100101; 2Beijing Institutes of Life Science, Chinese Academy of Sciences, Beijing 100101; 3Institute of Medicinal Plant Development, Chinese Academy of Medical Sciences, Peking Union Medical College, Beijing 100193, and 4University of Chinese Academy of Sciences, Beijing 100049, China Abstract Host alternation, an obligatory seasonal shifting between host plants of distant genetic relationship, has had significant consequences for the diversification and success of the superfamily of aphids. However, the underlying molecular mechanism remains unclear. In this study, the molecular mechanism of host alternation was explored through a large-scale gene expression analysis of the mealy aphid Hyalopterus persikonus on winter and summer host plants. More than four times as many unigenes of the mealy aphid were significantly upregulated on summer host Phragmites australis than on winter host Rosaceae plants. In order to identify gene candidates related to host alternation, the differentially expressed unigenes of H. persikonus were compared to salivary gland expressed genes and secretome of Acyrthosiphon pisum. Genes involved in ribosome and oxidative phosphorylation and with molecular functions of heme–copper terminal oxidase activity, hydrolase activity and ribosome binding were potentially upregulated in salivary glands of H. persikonus on the summer host. Putative secretory proteins, such as detoxification enzymes (carboxylesterases and cytochrome P450s), antioxidant enzymes (peroxidase and superoxide dismutase), glutathione peroxidase, glucose dehydrogenase, angiotensin-converting enzyme, cadherin, and calreticulin, were highly expressed in H. persikonus on the summer host, while a SCP GAPR-1-like family protein and a salivary sheath protein were highly expressed in the aphids on winter hosts. These results shed light on phenotypic plasticity in host utilization and seasonal adaptation of aphids. Key words aphid; host alternation; parasite-host interaction; phenotypic plasticity; salivary gland; transcriptome Introduction used as biological models to study insect–plant interac- tions, symbiosis, virus vectoring and the developmen- Aphids constitute one of the most important groups of sap- tal causes of extreme phenotypic plasticity (International sucking insects that comprise major pests of agriculture, Aphid Genomics Consortium, 2010). Most aphids present horticulture and forestry. However, aphids are also widely evident specialization on different host plants and use lim- ited numbers of host plants in monophagy or oligophagy Correspondence: Feng Cui and Le Kang, State Key Labo- (Moran, 1988). Even polyphagous aphids can conduct ratory of Integrated Management of Pest Insects & Rodents, intraspecific specialization, leading to the formation of Institute of Zoology, Chinese Academy of Sciences, 1 Beichen host biotypes (Eastop, 1986). Many aphids display a re- West Road, Beijing 100101, China. Tel: +86 10 64807218; markably complex life cycle on different host plants, on fax: +86 10 64807099; email: [email protected], [email protected] which cyclical parthenogenesis is combined with the obli- ∗These authors equally contributed to this work. gate use of two unrelated host plants at different seasons, 431 C 2016 Institute of Zoology, Chinese Academy of Sciences 432 N.Cuietal. entailing migration in spring from the primary (winter) ation (Peccoud et al., 2009). A genome-wide scan revealed host to the secondary (summer) host, and vice versa in au- that regions enclosing three salivary protein genes and tumn (Blackman & Eastop, 2000). This obligate seasonal olfactory receptor genes are likely associated with host shifting between host plants of distant genetic relationship plant adaptation and ecological speciation in pea aphids is defined as host alternation or heteroecy, which could (Jaquiery et al., 2012). Proteins involved in glycolysis, tri- have significant consequences for speciation (Moran, carboxylic acid cycle, and protein and lipid synthesis are 1988). Studies on host alternation are important for dis- downregulated, whereas cytoskeleton-related proteins are closing phenotypic plasticity in host utilization and sea- overexpressed during host plant shifting in Myzus per- sonal adaptation of aphids. sicae (Francis et al., 2006). However, large-scale gene As a unique characteristic of aphids, host alternation expression analyses clarifying the molecular mechanisms is crucial to the existence of aphid species that undergo of host alternation and adaptation in aphids are limited. heteroecy. Several reasons explain host alternation of Saliva secreted from the aphids’ salivary glands is be- aphids, such as the seasonal nutrition complement sup- lieved to deliver effector proteins that overcome plant plied by primary and secondary host plants (Kennedy & defenses (Hogenhout & Bos, 2011; Will et al., 2013). Stroyan, 1959), helping aphids escape from their natural Identification of saliva proteins has been carried out in enemy (Way & Banks, 1968) and the resistant response several aphid species (Cherqui & Tjallingii, 2000; Cooper of the host plant (Williams & Whitham, 1986). In ad- et al., 2010; Cooper et al., 2011; Vandermoten et al., dition, host alternation is related to the formation of in- 2014). A catalog of 42 candidate effector proteins from sect gall and polymorphism. Gall aphids are forced to the salivary gland of A. pisum and glucose oxidase, glu- alternate host plants after spring as two different types cose dehydrogenase, nicotinamide adenine dinucleotide of alate viviparous females when premature leaves that dehydrogenase, α-glucosidase and α-amylase from M. they use to form galls reduce (Lambers, 1966; Williams persicae saliva have been identified using a combined & Whitham, 1986). One of the best-known examples proteomic and transcriptomic approach (Harmel et al., of host alternation involves Hyalopterus persikonus,a 2008; Carolan et al., 2011). Effectors in saliva have been species of mealy aphid. The Hyalopterus genus contains proven to play key roles in the interaction between M. another two mealy aphid species, Hyalopterus pruni and persicae and different host plants (Bos et al., 2010) and Hyalopterus amygdali (Mosco et al., 1997; Poulios et al., plants, in return, react in various ways (Clark et al., 2014; 2007; Lozier et al., 2008). Hyalopterus aphids have been Zebelo & Maffei, 2015). reported as serious worldwide pests to stone fruits be- Transcriptome sequencing is a powerful tool to reveal cause of their potential for rapid population growth and gene expression and regulation profiles of an organism dispersal over great distances during migratory periods. in response to a changing environment from the perspec- They take Rosaceae plants, such as almond and peach, tive of a whole genome. In this study, we compared the as primary hosts, whereas the secondary hosts typically gene expression profiles of H. persikonus populations include reeds. When winged forms migrate to secondary living on winter and summer host plants to provide a hosts, the aphids are cyclically parthenogenetic and het- list of the potential genes involved in host alternation of eroecious throughout most of their range during spring aphids. Among these candidate genes, putative salivary and summer. In autumn, the aphids migrate back to their gland-expressed genes and secretory proteins presented primary hosts, where a single sexual generation occurs an important contribution to the host alternation of H. and results in an overwintering egg stage (Blackman & persikonus. Eastop, 2000). However, the molecular mechanism under- lying the success of Hyalopterus aphids in host alternation is unclear. Materials and methods Research on the molecular mechanisms of aphid host specialization or host shifting has not considerably pro- Aphid samples gressed. Evident genetic variation has been observed in host plant preference within and between pea aphid H. persikonus was collected from its three winter host (Acyrthosiphon pisum) populations collected from differ- plants, namely, Armeniaca mume Beauty mei, Prunus ent host plants (Ferrari et al., 2006; Ferrari et al., 2008). cistena cv. Pissardii and Amygdalus persica var. densa Genetic markers and tests of host plant specificity indi- Makino, at Tanggu, Tianjin (39°09 N 117°30 E), China, cated the existence of at least 11 host races in the pea and from one summer host plant, Phragmites australis,at aphid complex in Western Europe, forming a continuum Beijing (39°59 N 116°23 E), China, in October 2012. of population divergence toward virtually complete speci- Aphids were randomly sampled from different plants C 2016 Institute of Zoology, Chinese Academy of Sciences, 24, 431–442 Adaptations of aphid to different host plants 433 and pooled together as one sample for each host plant. aligned region of the best hit. Coding sequences shorter Adults were separated from nymphs and stored at -80°C than 90 bp were removed. Interproscan (Quevillon et al., prior to RNA extraction. Collecting locations were public 2005) (version 5.2–45.0) was used to identify protein do- greenbelts and open to the public. No specific permissions