You’re Invited to Talia Head’s PhD Exit Seminar

Join us for an engaging presentation by Talia Head, PhD candidate, as she discusses her groundbreaking research on the physiological regulation of molting in decapod crustaceans. In her seminar, Talia will explore the roles of two key hormones—Molt-Inhibiting Hormone (MIH) and ecdysteroids—and their influence on the molting process.

Talia’s work delves into the complex mechanisms behind how these hormones interact, focusing particularly on the protein PKG and its critical role in regulating ecdysteroid production. Her findings offer new insights into hormonal regulation in crustaceans and lay the groundwork for future research in animal biology.

Why Attend?

• Gain a deeper understanding of hormonal control in crustacean biology.
• Learn about the role of PKG in regulating molting and ecdysteroid synthesis.
• Engage with cutting-edge research that opens doors to new areas of scientific exploration.

Can’t attend in-person? Join us on Zoom!

• Zoom link: col.st/Q5C02
• Meeting ID: 978 5546 6083
• Passcode: 961339

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We hope you can join us to support Talia and learn about this fascinating area of research.

Abstract

Physiological regulation of molting in decapods is predominantly coordinated by two hormones, the peptide molt-inhibiting hormone (MIH), and steroid molting hormones termed ecdysteroids. MIH is produced and secreted by the X-organ/sinus gland complex located in the eyestalk ganglia and negatively regulates the production of ecdysteroids in the molting gland (Y-organ, YO). MIH signaling begins with a cAMP-dependent triggering phase followed by a cGMP-dependent summation phase which ultimately leads to inhibition of mTORC1. The involvement of cGMP in MIH signaling implicates the activity of cGMP-dependent protein kinase (PKG), although the downstream effects of PKG remain unknown. The goal of this work was to phylogenetically characterize PKG in crustaceans, characterize the physiological effects of PKG-inhibition on YO ecdysteroid synthesis, and identify potential substrates and downstream effects of MIH-dependent PKG activity in the YO. Two genes encoding PKG, pkg1 and pkg2, were identified in crustaceans and are conserved across metazoans. Alternative splicing of the PKG1 N-terminal yields three PKG1α and one PKG1β isoform in crustaceans, consistent with isoforms seen in characterized model species. PKG1 sequences with a 14- to 17- amino acid insertion within the kinase domain were identified in ten decapods and one stomatopod, and may indicate that alternative splicing occurs outside of the N-terminal. In vitro assays of paired YOs incubated with MIH and PKG inhibitors were used to assess the effects of PKG activity on ecdysteroidogenesis. In the presence of MIH, inhibition of both PKG1 and PKG2 increased ecdysteroid synthesis relative to MIH alone, whereas PKG2 inhibition enhanced the effects of MIH. These data indicate that the two PKG isoforms have opposing roles in modulating ecdysteroidogenesis via MIH signaling in YOs. Specifically, PKG1 plays a dominant role in MIH signaling by inhibiting ecdysteroid synthesis, while PKG2 counters that inhibition and maintains basal ecdysteroidogenesis in the intermolt YO. LC-MS/MS analysis of phosphopeptides enriched from PKG-inhibited YOs revealed several novel potential substrates of PKG in the YO, providing ample ground for future work.