Optogenetic Control of Subcellular Protein Location and Signaling in Vertebrate Embryos.

This chapter describes the use of optogenetic heterodimerization in single cells within whole-vertebrate embryos. This method allows the use of light to reversibly bind together an "anchor" protein and a "bait" protein. Proteins can therefore be directed to specific subcellular compartments, altering biological processes such as cell polarity and signaling. I detail methods for achieving transient expression of fusion proteins encoding the phytochrome heterodimerization system in early zebrafish embryos (Buckley et al., Dev Cell 36(1):117-126, 2016) and describe the imaging parameters used to achieve subcellular light patterning

A Light Oxygen Voltage Receptor Integrates Light and Temperature

Sensory photoreceptors enable organisms to adjust their physiology, behavior, and development in response to light, generally with spatiotemporal acuity and reversibility. These traits underlie the use of photoreceptors as genetically encoded actuators to alter by light the state and properties of heterologous organisms. Subsumed as optogenetics, pertinent approaches enable regulating diverse cellular processes, not least gene expression. Here, we controlled the widely used Tet repressor by coupling to light oxygen voltage LOV modules that either homodimerize or dissociate under blue light. Repression could thus be elevated or relieved, and consequently protein expression was modulated by light. Strikingly, the homodimeric RsLOV module from Rhodobacter sphaeroides not only dissociated under light but intrinsically reacted to temperature. The limited light responses of wild type RsLOV at 37 C were enhanced in two variants that exhibited closely similar photochemistry and structure. One variant improved the weak homodimerization affinity of 40 M by two fold and thus also bestowed light sensitivity on a receptor tyrosine kinase. Certain photoreceptors, exemplified by RsLOV, can evidently moonlight as temperature sensors which immediately bears on their application in optogenetics and biotechnology. Properly accounted for, the temperature sensitivity can be leveraged for the construction of signal responsive cellular circuit

SYSTEMS OF SETS OF LENGTHS: TRANSFER KRULL MONOIDS VERSUS WEAKLY KRULL MONOIDS

Transfer Krull monoids are monoids which allow a weak transfer homomorphism to a commutative Krull monoid, and hence the system of sets of lengths of a transfer Krull monoid coincides with that of the associated commutative Krull monoid. We unveil a couple of new features of the system of sets of lengths of transfer Krull monoids over finite abelian groups G, and we provide a complete description of the system for all groups G having Davenport constant D(G) = 5 (these are the smallest groups for which no such descriptions were known so far). Under reasonable algebraic finiteness assumptions, sets of lengths of transfer Krull monoids and of weakly Krull monoids satisfy the Structure Theorem for Sets of Lengths. In spite of this common feature we demonstrate that systems of sets of lengths for a variety of classes of weakly Krull monoids are different from the system of sets of lengths of any transfer Krull monoid