Influência de colônias reprodutivas de aves marinhas sobre populações vegetais nas ilhas Shetlands do Sul, Antártica, sob uma abordagem molecular

Abstract

Antarctica is the southernmost continent of the globe, and is also the coldest one, whith 96% of its territory permanently ice-covered. Despite the lowest temperatures, high altitudes and the strongest winds, it is home to a large biodiversity. Antarctic seabirds are abundant and takes up much of the coast during the breeding season, which occurs in the austral summer period, from October to March, ice-free period in the maritime Antarctic. Macronectes giganteus, popularly known as South Giant Petrel, is one of the species that occupy these ice-free areas for reproduction, in addition to penguins, skuas, gulls and petrels. The breeding areas of seabirds are often associated with plant communities and populations, among them algae, lichens, mosses and flowering plants. The mosses Sanionia uncinata (Hedw.) Loeske and Andreaea regularis C. Muell., are present as vast green formations, joined by other species as the only two native species of flowering plant in the region - Deschampsia antarctica Desv. and Colobanthus quitensis (Kunth) Bartl. The D. antarctica is a very common hairgrass in the Antarctic environment, and is associated with breeding colonies of seabirds. These sites are large deposits of guano, because seabirds return systematically each year, forming large breeding colonies with tens, hundreds or even thousands of individuals. Due to this large supply of guano, the soil becomes a deposit of minerals, mainly of nitrogen, increasing tremendously the soil contents of ammonium and nitrate. The problem is that not all vegetation support such high quantities of these substances, so different plant species show trends in the mechanisms of tolerance to stress by ammonium, which have been proven at the molecular level. In recent years, genetic regulators sensitive to NH4+ were identified in Arabidopsis thaliana and genes that were associated with sensitiveness to ammonia all showed responses at the root level, referencing the absorption and ammonia concentration by the root system of the plants. The aim of this study was to investigate and to analyze the influence of breeding colonies of seabirds on plant populations in the South Shetland Islands, Antarctica, from a molecular perspective. From the analysis of the collected samples using the RNA-seq and qRT-PCR approach, it was possible to identify a single differential gene, which was significantly expressed in D. antarctica. The LOC_Os06g16380 gene among the sampled treatments (control, 1m and 10m), showed higher expression coming 1m near breeding areas of M. giganteus. The gene differentially expressed in this work has been described in literature and was related to Heading date I gene (Hd1) found in rice, since they are located in the same region of the transcriptome. Our results suggest that LOC_Os06g16380 gene is associated with the plants ability to tolerate high amounts of ammonium, as soil analysis demonstrated larger contents of ammonium in the nearest sampling sites (1m) of breeding areas of seabirds.