Diapause is a critical eco-physiological adaptation for winter survival in the West Nile Virus vector, Culex pipiens, but little is known about the molecular mechanisms that distinguish diapause from non-diapause in this important mosquito species. We used Illumina RNA-seq to simultaneously identify and quantify relative transcript levels in diapausing and non-diapausing adult females. Among 65,623,095 read pairs, we identified 41 genes with significantly different transcript abundances between these two groups. Transcriptome divergences between these two phenotypes include genes related to juvenile hormone synthesis, anaerobic metabolism, innate immunity and cold tolerance.

Biomolecular condensates appear throughout the cell serving a wide variety of functions. Many condensates appear to form by the assembly of multivalent molecules, which produce phase-separated networks with liquidlike properties. These networks then recruit client molecules, with the total composition providing functionality. Here we use a model system of poly-SUMO and poly-SIM proteins to understand client−network interactions and find that the structure of the network plays a strong role in defining client recruitment and thus functionality. The basic unit of assembly in this system is a zipperlike filament composed of alternating poly-SUMO and poly-SIM molecules. These filaments have defects of unsatisfied bonds that allow for both the formation of a 3D network and the recruitment of clients. The filamentous structure constrains the scaffold stoichiometries and the distribution of client recruitment sites that the network can accommodate. This results in a nonmonotonic client binding response that can be tuned independently by the client valence and binding energy. These results show how the interactions within liquid states can be disordered yet still contain structural features that provide functionality to the condensate.

The taxonomy of Culex pipiens complex of mosquitoes is still debated, but in North America it is generally regarded to include Culex pipiens pipiens, Culex pipiens molestus, and Culex quinquefasciatus (or Culex pipiens quinquefasciatus). Although these mosquitoes have very similar morphometry, they each have unique life strategies specifically adapted to their ecological niche. Differences include the capability for overwintering diapause, bloodmeal preference, mating behaviors, and reliance on blood meals to produce eggs. Here, we used RNA-seq transcriptome analysis to investigate the differential gene expression and nucleotide polymorphisms that may link to the divergent traits specifically between Cx. pipiens pipiens and Cx. pipiens molestus.

Biomolecular condensates appear throughout the cell serving a wide variety of functions. Many condensates appear to form by the assembly of multivalent molecules, which produce phase separated networks with liquid-like properties. These networks then recruit client molecules, with the total composition providing functionality. Here we use a model system of poly-SUMO and poly-SIM proteins to understand client-network interactions and find that the structure of the network plays a strong role in defining client recruitment, and thus functionality. The basic unit of assembly in this system is a zipper-like filament composed of alternating poly-SUMO and poly-SIM molecules.These filaments have defects of unsatisfied bonds that allow for both the formation of a 3D network and the recruitment of clients. The filamentous structure constrains the scaffold stoichiometries and the distribution of client recruitment sites that the network can accommodate. This results in a non-monotonic client binding response that can be tuned independently by the client valence and binding energy. These results show how the interactions within liquid states can be disordered yet still contain structural features that provide functionality to the condensate. I. INTRODUCTIONMany cellular structures have been shown to form by the spontaneous condensation of biomolecules into liquidlike states [1,2], often through liquid-liquid phase transitions. While these condensates may contain hundreds of different molecules, typically only a small number of molecules with high interaction valence and high connectivity to other molecules in the structure contribute strongly to phase separation [3][4][5]. These are said to have scaffoldlike properties depending on how strongly they promote phase separation. The remaining molecules, which exhibit client-like properties, are recruited through interactions with scaffolds [6,7]. Together, the collection of molecules in a condensate determines its functionality.Since the molecules driving phase separation are multivalent, polymer-like species, many treatments of condensate formation are based on polymer theories [8][9][10][11]. In particular, scaffold condensation can be understood as the interaction between attractive stickers separated by inert spacers [11,12]. These efforts explain universal features of condensates, such as how multivalency can amplify the effect of weak interactions to tune the phase coexistence line to within physiologically relevant regions of phase space (e.g. physiological concentrations) [8]. However, there are also many non-universal features of biomolecular condensates. Experiments are revealing a striking diversity of functions performed by condensates [2,7,[13][14][15][16], and each of these assemblies will be under evolutionary pressure to optimize its specific function. This begs the question of how the disordered network of interactions within a liquid structure can affect its properties.