Ciliary Generation of a Peptidergic Sexual Signal

Abstract

Peptidergic intercellular communication occurs throughout the eukaryotes, and regulates a wide range of physiological and behavioral responses. Cilia are sensory and secretory organelles that both receive information from the environment and transmit signals. Cilia derived vesicles (ectosomes), formed by outward budding of the ciliary membrane, carry enzymes and other bioactive products; this process represents an ancient mode of regulated secretion. Our previous study revealed the presence of the peptide amidating enzyme, peptidylglycine α-amidating monooxygenase (PAM), in cilia and its key role in ciliogenesis. Furthermore, PAM and its amidated products are released in ciliary ectosomes from the green alga Chlamydomonas reinhardtii. One amidated product (GATI-amide) serves as a chemotactic modulator for C. reinhardtii gametes, attracting minus gametes while repelling plus gametes. Here we dissect the complex processing pathway that leads to formation of this amidated peptidergic sexual signal specifically on the ectosomes of plus gametes. We also identify a potential prohormone convertase that undergoes domain rearrangement during ectosomal secretion as a substrate for PAM. Analysis of this pathway affords insight into how single-celled organisms lacking dense core vesicles engage in regulated secretion, and provides a paradigm for understanding how amidated peptides that transmit sexual and other signals through cilia are generated.

Face dependent footprints of carpet-like graphene films grown on polycrystalline silicon carbide

“…The relatively thick MLG grown on the C-face does not pile in the AB Bernal stacked manner as in the Si-face. Instead, it presents a high azimuthal disorder as a consequence of the weak interaction with the substrate that confers to the multilayer system properties close to the individual single-layer [53,54,55]. All these circumstances have effects in the morphology of the grown graphene and are discussed below.…”