However, while many studies have analyzed the developmental and morphological aspects of gall induction, the molecular mechanisms used by the gall wasps to modify plant host physiology during cecidogenesis (i.e., gall formation) are unknown ( Giron et al., 2016 Nabity, 2016).Ĭynipid gall development by wasps can be divided into three major steps: (i) initiation, (ii) growth, and (iii) maturation ( Rohfritsch, 1992 Stone et al., 2002). Overall, this suggests gall wasps have evolved a genuine molecular dialogues with the plant that allows establishment of a precise developmental program resulting in the formation of specific galls as well as preventing or diverting plant defenses. In consequence, galls are considered to be the extended phenotypes of galler genes ( Dawkins, 1982 Stone and Schönrogge, 2003). Mature galls formed by members of the same genus may differ enormously in size, color and shape ( Stone and Schönrogge, 2003 Bailey et al., 2009), and are diagnostic of the inducing gall wasp species. ![]() The diversity observed in cynipid gall morphology is the result of variation in the targeted plant organ ( Shorthouse et al., 2005) and in gall tissues that develop outside the larval chamber, such as surrounding layers of woody or spongy tissue, complex air spaces within the gall, surface coats of sticky resins, hairs or spines ( Stone and Schönrogge, 2003), and extrafloral nectaries ( Nicholls et al., 2016 Pierce, 2019). The cynipid larva completes its entire development within this chamber. The larval chamber, which is structurally similar in almost all cynipid galls ( Stone et al., 2002), is lined with nutritive plant tissues on which the larva feeds, and is surrounded by a thin wall of sclerenchyma. Structurally, cynipid galls can be divided into two parts: the larval chamber and the outer gall. Gall tissues provide food and physical protection for the larvae developing within them ( Cornell, 1983 Price et al., 1987 Bailey et al., 2009). These gall wasps have the capacity to modify plant host physiology, resulting in the development of complex gall structures that resemble novel plant organs but which are never produced by healthy plants ( Harper et al., 2004). While some species gall non-woody herbs ( Ronquist and Liljeblad, 2001 Abe et al., 2007), the most familiar species belong to two gall wasp tribes, the Cynipini and Diplolepidini, which induce galls on oak trees and rose bushes, respectively ( Ronquist and Liljeblad, 2001 Ronquist et al., 2015). ![]() Around 1400 species of gall wasps parasitizing different plants have been described ( Ronquist et al., 2015). Although most cynipoid lineages are parasitoids of insect larvae, the well-described family Cynipidae consists entirely of plant-galling wasps ( Ronquist, 1999 Ronquist et al., 2015). By exploring gall wasp effectors, this study is a first step toward understanding the molecular mechanisms underlying cynipid gall induction in woody plants, and the recent sequencing of oak and rose genomes will enable study of plant responses to these factors.Ĭynipoid wasps (Hymenoptera: Apocrita) constitute a diverse lineage of plant and insect parasites. ![]() We find no evidence of virus-related gene expression, in contrast to many non-cynipid parasitoid wasps. We also identify gall wasp cellulases that could be involved in observed local lysis of plant tissue following oviposition, and which may have been acquired from bacteria by horizontal gene transfer. Some genes highly expressed in venom glands and ovaries may act to suppress early plant defense signaling. We identify for the first time a set of maternally expressed gall wasp proteins potentially involved in the interaction with the plant. ![]() The relative expression levels of contigs were estimated to identify the most expressed gene sequences in each tissue. De novo assembled and annotated contigs were compared to sequences from phylogenetically related parasitoid wasps. To gain insight into wasp factors that might be involved in the initial induction of galls on woody plants, we performed high throughput (454) transcriptome analysis of ovaries and venom glands of two cynipid gall wasps, Biorhiza pallida and Diplolepis rosae, inducing galls on oak and rose, respectively.
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