Reed, E. H. | Search bioRxiv

bioRxiv2024

Molecular phylogenetics illuminates evolutionary history and hidden diversity of Australian cave crickets (Orthoptera: Rhaphidophoridae)

Cave crickets (Orthoptera: Rhaphidophoridae) are a globally distributed group of insects found in dark, humid microhabitats including natural caves, alpine scree, and forest litter. Ten extant subfamilies are currently recognised and Macropathinae, which comprises the entirety of the fauna in South America, South Africa, Australia, and New Zealand, is thought to be the most ancient of these. The New Zealand rhaphidophorid fauna comprises high phylogenetic diversity throughout its mesic zone, with most species occurring above-ground. In contrast, the Australian fauna is poorly known, with an apparently greater relative proportion of species utilising caves as refugia. A robust phylogenetic framework is needed to underpin future taxonomic work on the group and potentially contrasting patterns of taxonomic diversity within Macropathinae. Here, we performed fossil-calibrated phylogenetic analysis using whole mitochondrial genomes and nuclear markers to reconstruct the evolutionary history of Macropathinae, with a focus on the Australian fauna. By dramatically increasing taxon sampling relative to past studies, we recovered the Australian fauna as rampantly polyphyletic, with the remaining Macropathinae nested amongst six distinct Australian lineages. Deep divergences between major clades imply additional Australian lineages remain undetected, either due to extinction or sampling bias, and have likely confounded past biogeographic signal. We inferred the radiation of Macropathinae began during the Lower Cretaceous prior to the fragmentation of Gondwana with a potential Pangaean origin for Rhaphidophoridae. Finally, we found evidence for several undescribed taxa of Australian Rhaphidophoridae, all of which qualify as short-range endemics, and discuss the conservation implications of these restricted distributions.

evolutionary biology↗

bioRxiv2020

Clustering-based positive feedback between a kinase and its substrate enables effective T-cell receptor signaling

Protein clusters and condensates are pervasive in mammalian signaling. Yet how the signaling capacity of higher-order assemblies differs from simpler forms of molecular organization is still poorly understood. Here, we present an optogenetic approach to switch between light-induced clusters and simple protein heterodimers with a single point mutation. We apply this system to study how clustering affects signaling from the kinase Zap70 and its substrate LAT, proteins that normally form membrane-localized clusters during T cell activation. We find that light-induced clusters of LAT and Zap70 trigger potent activation of downstream signaling pathways even in non-T cells, whereas one-to-one dimers do not. We provide evidence that clusters harbor a local positive feedback loop between three components: Zap70, LAT, and Src-family kinases that bind to phosphorylated LAT and further activate Zap70. Overall, our study provides evidence for a specific role of protein condensates in cell signaling, and identifies a simple biochemical circuit that can robustly sense protein oligomerization state. Highlights- A general system for studying the role of protein clusters versus dimers. - Membrane clusters of the kinase Zap70 and its substrate LAT trigger potent downstream signaling. - Clustering Zap70 with LAT is required for full activation of Zap70 kinase activity. - A positive feedback loop connects phosphorylated LAT to Zap70 activation via Src-family kinases.

cell biology↗