ABSTRACT: Whole genome sequencing and transcriptome sequencing of electric fishes to investigate molecular nature and convergent evolution of electric organs
Project description:Hybridization can act as a catalyst for rapid phenotypic evolution by introducing novel allelic combinations, which can affect hybrid phenotype through changes in gene expression. The African weakly electric fish use their muscle-derived electric organ to produce electric organ discharge (EOD) for electrocommunication and electrolocation. The EOD in genus Campylomormyrus and cross-species hybrids is usually species-specific and varies during ontogeny. We compared the gene expression patterns and allele specific expression between juvenile and adult individuals in C. compressirostris (EOD duration 0.4 ms in juvenile and 0.4 ms in adult), C. rhynchophorus (EOD duration 5 ms in juvenile and 40 ms in adult) and their hybrid (EOD duration 0.4 ms in juvenile and 4 ms in adult). Differentially expressed genes between juveniles and adults were highly enriched in “membrane”, “plasma membrane” and “cytoplasm” Go Ontogeny terms. We detected several potassium channel-related genes (e.g. KCNJ2, ADCYAP1) that are potentially involved in the EOD development during ontogeny. The alleles from C. compressirostris show dominant expression in the hybrid at juvenile and adult life stages. KCNJ2 is the only gene that exhibits allelic dominance of C. rhynchophorus allele, and has an increasing expression during ontogeny in this allele. This suggests that the EOD development in hybrids could be related to the increasing allelic expression of the C. rhynchophorus allele under the scenario of overall dominance of C. compressirostris alleles. Our study sheds light in the evolution of the electric organ discharge in electric fishes and on the role of introgressive hybridization in complex phenotypic traits.
Project description:Electric fishes have independently evolved six times. Most of these fish are weakly electric and they use their discharge mainly for orientation and communication. In the African weakly electric fish genus Campylomormyrus, electric organ discharge (EOD) signals are strikingly different in shape and duration among closely related species, they contribute to pre-zygotic isolation and may have triggered an adaptive radiation. We performed mRNA sequencing on electric organs (EOs) and skeletal muscle (SMs; from which the EOs derive) from three species with short (0.4 ms), medium (5 ms), and long (40 ms) EODs and two different cross-species hybrids. Using pairwise comparison of differential gene expression between EOs and SMs, we identified 1,444 up regulated genes in EO shared by all five species/hybrids cohorts, rendering them candidate genes for EO-specific properties in Campylomormyrus. To understand how gene expression contributes to the variation in EOD duration, we made cross species comparisons among species and tissue. We identified three types of EOD-duration-related expression patterns and several candidate genes, including KCNJ2, KLF5 and SLC24a2, their upregulation may contribute to increased EOD duration, along with a down-regulated gene KCNK6. Hybrids between a short (C. compressirostris) and a long (C. rhynchophorus) discharging species exhibit EODs of intermediate duration and showed imbalanced expression of KCNJ2 alleles. The preferential expression of the C. rhynchophorus allele is in line with a higher expression level in that parental species and points towards a cis-regulatory difference at this locus, relative to EOD duration. A further candidate gene, KLF5, is a transcription factor potentially balancing potassium channel gene expression, a crucial process for the formation of an EOD. Unraveling the genetic basis of the species-specific modulation of the EOD in Campylomormyrus is crucial for understanding the adaptive radiation of this emerging model taxon of ecological (perhaps even sympatric) speciation.
Project description:Resource limitation is a major driver of ecological and evolutionary dynamics of organisms. Short-term responses to resource limitation include plastic changes in molecular phenotypes including protein expression. Yet little is known about the evolution of the molecular phenotype under longer-term resource limitation. Here, we combine experimental evolution of the green alga Chlamydomonas reinhardtii under multiple different non-substitutable resource limitation regimes with proteomic measurements to investigate evolutionary adaptation of the molecular phenotype. We demonstrate convergent proteomic evolution of core metabolic functions, including the Calvin-Benson cycle and gluconeogenesis, across different resource limitation selection environments. We did not observe proteomic changes consistent with optimized uptake of the different particular limiting resources.
Project description:Elasmobranch fishes, including sharks, rays, and skates, use specialized electrosensory organs called Ampullae of Lorenzini to detect extremely small changes in environmental electric fields. Electrosensory cells within these ampullae are able to discriminate and respond to minute changes in environmental voltage gradients through an as-yet unknown mechanism. Here we show that the voltage-gated calcium channel CaV1.3 and big conductance calcium-activated potassium (BK) channel are preferentially expressed by electrosensory cells in little skate (Leucoraja erinacea) and functionally couple to mediate electrosensory cell membrane voltage oscillations, which are important in the detection of specific, weak electrical signals. Both channels exhibit unique properties compared with their mammalian orthologues to support electrosensory functions: structural adaptations in CaV1.3 mediate a low voltage threshold for activation, while alterations in BK support specifically tuned voltage oscillations. These findings reveal a molecular basis of electroreception and demonstrate how discrete evolutionary changes in ion channel structure facilitate sensory adaptation.
2017-03-01 | GSE93582 | GEO
Project description:Testing for convergent molecular evolution in Arctic Brassicaceae
Project description:Maize anthers, the male reproductive floral organs, express two classes of phased, small interfering RNAs (phasiRNAs). RNA profiling from ten sequential cohorts of staged maize anthers plus mature pollen revealed that 21-nt phased siRNAs (21-phasiRNAs) from 463 loci appear abruptly after germinal and initial somatic cell fate specification and then diminish, while 24-nt phased siRNAs (24-phasiRNAs) from 176 loci coordinately accumulate during meiosis and persist as haploid gametophytes differentiate into pollen. RNA sequencing of anther developmental mutants, together with in situ RNA hybridization detection of phasiRNA biogenesis factors, demonstrated that 21-phasiRNAs and 24-phasiRNAs are independently regulated. Furthermore, 21-phasiRNAs require epidermal cells while 24-phasiRNAs require functional tapetal cells. Maize phasiRNAs and mammalian PIWI-interacting RNAs (piRNAs) illustrate convergent evolution of small RNAs to support male reproduction. Examination of maize phasiRNAs by high throughput sequencing for RNA-seq, small RNA, and PARE profiling
Project description:Maize anthers, the male reproductive floral organs, express two classes of phased, small interfering RNAs (phasiRNAs). RNA profiling from ten sequential cohorts of staged maize anthers plus mature pollen revealed that 21-nt phased siRNAs (21-phasiRNAs) from 463 loci appear abruptly after germinal and initial somatic cell fate specification and then diminish, while 24-nt phased siRNAs (24-phasiRNAs) from 176 loci coordinately accumulate during meiosis and persist as haploid gametophytes differentiate into pollen. RNA sequencing of anther developmental mutants, together with in situ RNA hybridization detection of phasiRNA biogenesis factors, demonstrated that 21-phasiRNAs and 24-phasiRNAs are independently regulated. Furthermore, 21-phasiRNAs require epidermal cells while 24-phasiRNAs require functional tapetal cells. Maize phasiRNAs and mammalian PIWI-interacting RNAs (piRNAs) illustrate convergent evolution of small RNAs to support male reproduction. Examination of maize phasiRNAs by high throughput sequencing for RNA-seq, small RNA and PARE profiling.
Project description:Maize anthers, the male reproductive floral organs, express two classes of phased, small interfering RNAs (phasiRNAs). RNA profiling from ten sequential cohorts of staged maize anthers plus mature pollen revealed that 21-nt phased siRNAs (21-phasiRNAs) from 463 loci appear abruptly after germinal and initial somatic cell fate specification and then diminish, while 24-nt phased siRNAs (24-phasiRNAs) from 176 loci coordinately accumulate during meiosis and persist as haploid gametophytes differentiate into pollen. RNA sequencing of anther developmental mutants, together with in situ RNA hybridization detection of phasiRNA biogenesis factors, demonstrated that 21-phasiRNAs and 24-phasiRNAs are independently regulated. Furthermore, 21-phasiRNAs require epidermal cells while 24-phasiRNAs require functional tapetal cells. Maize phasiRNAs and mammalian PIWI-interacting RNAs (piRNAs) illustrate convergent evolution of small RNAs to support male reproduction. Examination of maize phasiRNAs by high throughput sequencing for small RNA profiling
Project description:Convergent phenotypic evolution of the visual system via different molecular routes: How Neotropical cichlid fishes adapt to novel light environments