ESEB 2013 | XIV Congress of the European Society for Evolutionary Biology

Abstracts (first author)

Invited Speaker

Morph-specific circadian plasticity and G X E for juvenile hormone and gene expression in a wing-polymorphic cricket

Author(s): Zera AJ, Brisson JA, Nanoth Vellichirammal N

Summary:

The endocrine basis of phenotypic plasticity in insects has been the subject of considerable study and speculation for decades. Yet, detailed information on endocrine mechanisms is still uncommon, and many “classic” examples of endocrine plasticity are, in fact, only weakly supported by experimental data. Furthermore, an important aspect of plasticity, circadian plasticity, has remained virtually unstudied. During the past decade, the Zera laboratory has undertaken detailed studies of morph-specific JH titer variation in the wing-polymorphic cricket, Gryllus firmus. This species exhibits a classic life history trade-off consisting of a dispersing morph (LW; long-winged) that delays reproduction and a flightless morph (SW; short-winged) that exhibits enhanced early-age fecundity. An unanticipated and dramatic genotype (morph) x environment (time-of-day) interaction for the blood JH titer (i.e. genetic variation for circadian plasticity) was identified in this species. In the LW morph the JH titer rises and falls 20-100 fold within a few hours before and after lights-off in the laboratory or sunset in the field. Failure to take this rhythm into account can result in substantial errors in interpreting the role of JH in morph adaptation. The morph-specific JH titer rhythm appears to be common in cricket species; the JH cycle likely regulates some aspect of flight, which only occurs in the dispersing morph at night. A recent transcriptome study identified a morph-specific circadian rhythm with respect to global gene expression. Daily change in transcript abundance occurs for a greater number of genes in the LW than in the SW morph, and is more prominent than differences in expression between LW and SW morphs at the same time of day. Circadian plasticity and G X E are potentially common, important, but largely unstudied aspects of phenotypic plasticity and life history adaptation. Supported by NSF award IOS – 1122075 to AJZ

Abstracts (coauthor)

Transcriptomics of a life history trade-off in the wing polymorphic cricket (Gryllus firmus)

Author(s): Schilder, RJ, Vellichirammal NN, Wehrkamp C, Riethoven JM, Zera AJ, Brisson JA

Summary:

The sand cricket Gryllus firmus is a model species in the study of the trade-off between (flight) dispersal and fecundity associated with wing-polymorphism in insects. G. firmus females exist as either a flight capable, long-winged (LW(f)) morph that delays egg production or as a flight-incapable, short-winged (SW) morph with substantially elevated egg production. In addition, some adult LW(f) individuals partially degenerate their flight musculature, thus giving rise to a third morph (LW(h)), that exhibits the substantially increased egg production seen in the SW morph. Here we present findings of a transcriptomics study that examined molecular mechanisms underlying plasticity in flight muscle and fat body function among the G. firmus morphs. Expression of genes encoding proteasome components was significantly enhanced in LW(h) flight muscle, however we observed a striking, nearly complete absence of differences in flight muscle sarcomere gene expression between LW(f) and LW(h) morphs. This indicates that flight muscle histolysis in the LW(h) morph is a highly controlled and selective process, and that maintenance of non-histolyzed fibers in LW(h) flight muscle is controlled through gene expression patterns similar to that in the LW(f) morph. In addition, LW(h) morph flight muscle displayed a significant reduction in expression of genes encoding aspects of mitochondrial structure and metabolism, supportive of earlier enzymological and metabolic rate work in this species. Genes involved in triglyceride biosynthesis were significantly upregulated in LW(f) fat body tissue, while SW fat body exhibited substantially elevated expression of an insulin-like peptide known to regulated egg production in locusts, as well as a number of lectin-related proteins that function in immunity. We will discuss our findings with respect to the physiological and molecular mechanisms underlying the flight-fecundity trade-off in G. firmus and other insect species.

Anthony J. Zera

Abstracts (first author)

Morph-specific circadian plasticity and G X E for juvenile hormone and gene expression in a wing-polymorphic cricket

Abstracts (coauthor)

Transcriptomics of a life history trade-off in the wing polymorphic cricket (Gryllus firmus)

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