| Alga is an important factor for marine economic,kelp is an important accumulators of iodine due to containing special characteristics of iodine absorption.Thus the process of absorption,storage and release of iodine in kelp is an important part in the biogeochemical iodine cycle.They accumulate iodine can be retained mainly in the form of iodide.It can react as an inorganic antioxidant in the immune response to effectively remove the reactive oxygen species(ROS).Upon oxidative stress,the iodide in kelp can be released to be oxidized in the surface and apoplast of the frond.The oxidants and the ozone layer can effect large amounts of I2 to be relased in the surface of kelp.Subsequently,the released of iodine molecules can be oxidized by the ozone to iodine oxides.Which are highly hygroscopic and thus form cloud condensation nuclei.This can indirectly have a negative impact on the ozone layer by causing damage.In the process of iodine metobolism,a key enzyme-vHPOs play an important catalytic role,which can catalyze the reaction of halide anions and hydrogen peroxide.In addition,the vHPOs may participate in regulating the adhesion and thickening the cell wall of kelp gametophytes and swim sporophytes.Therefore,to study the iodine mechanism in kelp has certain viability and high research value.The increasing of pCO2 in the atmosphere derived from anthropogenic activity and global climate change has led to global warming.As the result of the ocean absorbing up to 30% of CO2 in the atomosphere that has been derived from anthropenic acitivity has caused ocean acidifcation(OA).The marine environment is an important factor in the biogeochemical iodine cycle and the kelp are the larger accumulators of iodine.China,has the largest cultivation area and aquaculture production of kelp world wide.Increasing temperature and ocean acidification may affect the iodine metabolism in kelp which can lead to the effect of consumption of iodine for humans and have an affect on the biogeochemical iodine cycle.On account of iodine change in kelp following climate change will have influence both on human health and biogeochemical cycle of iodine.In this study,we will explore the response and regulation mechanism of the iodine metabolism in S.japonica to climate change in ecological and molecular aspects.Firstly,we set different temperature and acidification gradient to study the change of iodine in phenotype and molecular level.Secondly,vHPOs play an important catalytic role in iodine metabolism of kelp.On the basis of whole genome sequencing in S.japonica,phylogenetics analysis of vHPOs in several eukaryotic and prokaryotic arganisms were performed.The main results were as follows:1.In this part,we conducted experiments to study the separate and combined effects of temperature and pCO2 on effect of iodine metabolism in S.japonica and the results show remarkable effects.Firstly,we cultured S.japonica in a series of temperature(5?,10?,15?,20?,23?)and we find that there was significant variation of iodine content with the increase of temperature and the maximum occurred at 15 °C;Secondly,algal samples were bubbled with air/ CO2 mixture under the setting gradient(400?atm,700?atm,1000?atm,1500?atm,2000?atm),where pCO2 also showed dramatic effect on iodine content and the peak was present at 1000 ?atm;Thirdly,results of the combined effects of temperature and PCO2 show that they have coupling accelerate role.Also,the situ experiment in sea verify the result that ocean acidification can promote the growth and iodine content of S.japonica.Lastly,measurement of inorganic iodine speciation shows that the change of iodide is similar to the change of total iodine,while iodate iodine is little even not able to measure.2.In the S.japonica genome,17 vBPO and 58 vIPO genes were identified and annotated,and a phylogenetic analysis revealed that all of the vHPOs genes can be divided into three different subfamilies: vCPOs?vBPOs and v IPOs.Also,they form a monophyletic group sharing a common ancestor with the vCPO genes of fungi,after which they evolved independently in red and brown algae,and v IPO in kelp were evolved from the ancestor of vBPO.3.The v HPO genes identified in S.japonica showed diverse expression patterns in different tissues and during different developmental stages.In particular,vHPO gene expression was observed to be significantly up-regulated in the gametophytes.Among the sporophyte samples,the greatest number of vHPOs were expressed in the juvenile sporophytes,followed by the distal blades and rhizome.In addition,we analyze the results of transcriptome sequencing that S.japonica cultured in 20? and carbonation for 3h to explain the change in ecological.We find the molecular results were consistent with phenotypic change and they have eight vHPO genes up-regulated respectively. |
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