Response of key stress-related genes of the seagrass Posidonia oceanica in the vicinity of submarine volcanic vents

[摘要] Submarine volcanic vents are being used as natural laboratories to assessthe effects of increased ocean acidity and carbon dioxide (CO₂)concentration on marine organisms and communities. However, in the vicinityof volcanic vents other factors in addition to CO₂, which is the maingaseous component of the emissions, may directly or indirectly confound thebiota responses to high CO₂. Here we used for the first time theexpression of antioxidant and stress-related genes of the seagrassPosidonia oceanica to assess the stress levels of the species. Our hypothesis is that unknownfactors are causing metabolic stress that may confound the putative effectsattributed to CO₂ enrichment only. We analyzed the expression of 35antioxidant and stress-related genes of P. oceanica in the vicinity of submergedvolcanic vents located in the islands of Ischia and Panarea, Italy, andcompared them with those from control sites away from the influence ofvents. Reverse-transcription quantitative polymerase chain reaction(RT-qPCR) was used to characterize gene expression patterns.

Fifty-one percent of genes analyzed showed significant expression changes.Metal detoxification genes were mostly down-regulated in relation tocontrols at both Ischia and Panarea, indicating that P. oceanica does notincrease the synthesis of heavy metal detoxification proteins in response tothe environmental conditions present at the two vents. The up-regulation ofgenes involved in the free radical detoxification response (e.g., CAPX, SODCPand GR) indicates that, in contrast with Ischia, P. oceanica at the Panarea site facesstressors that result in the production of reactive oxygen species,triggering antioxidant responses. In addition, heat shock proteins were alsoactivated at Panarea and not at Ischia. These proteins are activated toadjust stress-accumulated misfolded proteins and prevent their aggregationas a response to some stressors, not necessarily high temperature.

This is the first study analyzing the expression of target genes in marineplants living near natural CO₂ vents. Our results call for contentionto the general claim of seagrasses as "winners" in a high-CO₂ world,based on observations near volcanic vents. Careful consideration offactors that are at play in natural vents sites other than CO₂ andacidification is required. This study also constitutes a first stepfor using stress-related genes as indicators of environmental pressures in achanging ocean.

[学科分类] 地球化学与岩石