Many organisms exhibit visually striking spotted or striped pigmentation patterns. Turing's reaction-diffusion model postulates that such periodic pigmentation patterns form when a local autocatalytic feedback loop and a long-range inhibitory feedback loop interact. At its simplest, this network only requires one self-activating activator that also activates a repressor, which inhibits the activator and diffuses to neighboring cells. However, the molecular activators and repressors fully fitting this versatile model remain elusive. Here, we characterize an R2R3-MYB activator and an R3-MYB repressor in monkeyflowers that correspond to Turing's model and explain how periodic anthocyanin spots form. Notably, disrupting this pattern impacts pollinator visitation. Thus, subtle changes in simple reaction-diffusion networks are likely essential contributors to the evolution of the remarkable diversity of periodic pigmentation patterns in flowers. MaintextPeriodic pigmentation patterns like the stripes of zebras, the spiral pigmentation of seashells, and the petal spots of many flowers have fascinated biologists and mathematicians for centuries. One proposed developmental explanation for how such periodic patterns form is Turing's reactiondiffusion model (1), in which dynamic and autonomous patterns are generated simply owing to the interaction of an activator and a repressor. The activator self-activates and activates the repressor, which then diffuses and inhibits the activator along the diffusion path. This mechanism amplifies initial cellular fluctuations into tissue-level spatial patterns (2-4). Computer simulations suggest that by tinkering with the diffusion constants and the kinetics of the activator-repressor interaction, this simple circuit can recapitulate the immense diversity of pigmentation patterns observed in nature (3). However, the molecular identities and dynamics of actual activator-repressor pairs that fulfill the classic Turing model for pigment patterning have remained elusive. Anthocyanin spots in flower petals provide an excellent empirical system to reveal the molecular basis for the formation and evolution of periodic pigmentation patterns. These patterns, which are highly diverse in the angiosperms even among different varieties of the same species (5,6), are known to serve as critical cues in plant-pollinator interactions (7-9); and the genetic network controlling anthocyanin pigment production is otherwise well described (10, 11).
The cichlid fishes of the East African Great Lakes are the largest extant vertebrate radiation identified to date. These lakes and their surrounding waters support over 2,000 species of cichlid fish, many of which are descended from a single common ancestor within the past 10 Ma. The extraordinary East African cichlid diversity is intricately linked to the highly variable geologic and paleoclimatic history of this region. Greater than 10 Ma, the western arm of the East African rift system began to separate, thereby creating a series of rift basins that would come to contain several water bodies, including the extremely deep Lakes Tanganyika and Malawi. Uplifting associated with this rifting backponded many rivers and created the extremely large, but shallow Lake Victoria. Since their creation, the size, shape, and existence of these lakes have changed dramatically which has, in turn, significantly influenced the evolutionary history of the lakes' cichlids. This paper reviews the geologic history and paleoclimate of the East African Great Lakes and the impact of these forces on the region's endemic cichlid flocks.
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The atypical pneumonia caused by SARS-CoV-2 is an ongoing pandemic and a serious threat to global public health. The COVID-19 patients with severe symptoms account for a majority of mortality of this disease. However, early detection and effective prediction of patients with mild to severe symptoms remains challenging. In this study, we performed proteomic profiling of urine samples from 32 healthy control individuals and 6 COVID-19 positive patients (3 mild and 3 severe). We found that urine proteome samples from the mild and severe COVID-19 patients with comorbidities can be clearly differentiated from healthy proteome samples based on the clustering analysis.Multiple pathways have been compromised after the COVID-19 infection, including the dysregulation of immune response, complement activation, platelet degranulation, lipoprotein metabolic process and response to hypoxia.We further validated our finding by directly comparing the same patients' urine proteome after recovery. This study demonstrates the COVID-19 pathophysiology related molecular alterations could be detected in the urine and the potential application of urinary proteome in auxiliary diagnosis, severity determination and therapy development of COVID-19.
One-sentence summary: Mutant analysis and transgenic experiments in the model plant 19 monkeyflower (Mimulus) identify a tetratricopeptide repeat protein required for chromoplast 20 development and carotenoid biosynthesis.
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