Anthony J. Zera
University of NebraskaSchool of Biological Sciences
1180 "T" Street
Lincoln, Nebraska, 68404
United States
Website
Abstracts (first author)
Morph-specific circadian plasticity and G X E for juvenile hormone and gene expression in a wing-polymorphic cricket
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