Perfil transcriptômico do tambaqui Colossoma macropomum (Cuvier, 1818) revela adaptação local de duas populações artificialmente criadas e plasticidade regional sobre um cenário extremo de mudança climática

Abstract

Human-induced climate change is considered a severe threat to environmental, economic, and social sustainability framework, inducing disturbances at all levels of biodiversity. Overall, two mechanisms of adaptive responses by organisms are expected in the face of ongoing environmental changes: phenotypic plasticity and evolutionary change. Plasticity shifts short-term responses producing different phenotypes, whereas long-term responses through mutations and natural selection are expected from the evolutionary point of view. Phenotypic plasticity in organisms experimentally exposed to variable abiotic conditions has been investigated over the last few years. Herein, the molecular plasticity of tambaqui Colossoma macropomum (Cuvier, 1818), an economically important species for Brazilian aquaculture, was assessed through two unprecedented approaches: i) a comparative transcriptome profile evaluation in two farmed tambaqui populations (Chapter 1); and ii) the investigation of the effects of an extreme climate change scenario on transcripts differentially expressed compared to the current scenario of the same two farmed populations (Chapter 2). Firstly, a total of 20 tambaqui juveniles were ex-situ sampled in two fish farms located in the Northern (Balbina Center of Technology, Training and Production in Aquaculture, CTTPA – SEPA/SEPROR, Balbina/AM) and Southeast (Brumado Fish Farming, Mogi Mirim/SP) regions from Brazil. Secondly, 200 tambaqui juveniles from the same populations were purchased, transported to Manaus/AM, and acclimated to laboratory conditions. Thirty-six tambaqui juveniles of both populations were artificially exposed during 30 days in simulated climate scenarios: current (baseline condition) and extreme such as foreseen in RCP8.5, according to a recent IPCC report (2014). RNA sequencing analysis (RNA-Seq) from 18 libraries of the liver tissue revealed 2,765 differentially expressed genes, whose terms were assigned into a range of molecular functions (5,311), biological processes (5,610) and cellular components (1,202). Overall, responsive genes to cellular stress were upregulated in tambaquis of both different latitudes and after exposure to an extreme climate scenario, such as YWHAE, MAPKAPK2, ATXN3 (cellular responses to heat); KCNMA, nrp1a, Ireb2, Pink1, Slc29a1, LONP1, Nop53, ldha (hypoxia responses); and sod, Gpx4, IDH1, LONP1, NDUFS2, TXN2, ATOX1 (oxidative stress responses). The regulation of DEGs suggests different strategies for local adaptation of populations raised in climatically variable regions (different latitudes), as well as regional plasticity to deal with climate changes projected for the end of the century by IPCC.