Study On The Environmental Adaptability And Response Mechanism To High Temperature Stress Of Pterocladiella Capillacea

Pterocladiella capillacea is large-scale economic red algae.It is used as edible,medicinal and agar industrial raw materials,possessing high development values.As one of the main species in the southern sea area,P.capillacea can provide an important habitat for marine creatures,optimize the marine environment and contribute to the growth of marine resources.In recent years,environment of immediate offshore area is seriously unbalanced due to the interference of human activities and the impact of global warming.As one of the excellent sources of agar in the south,wild resources can not provide sufficient raw materials,which undoubtedly limits the development and utilization of P.capillacea.Therefore,it is of great practical significance to study the environmental adaptability of P.capillacea to realize artificial cultivation.In this paper,the effects of environmental factors such as temperature,salinity and light intensity on the growth and response mechanism of P.capillacea under high temperature stress were studied.The main results are as follows:（1）Effects of temperature（16℃,19℃,22℃,25℃,28℃）,salinity（15 psu,20 psu,25psu,30 psu,35 psu）,light intensity(40μmol·m^-2·s^-1,80μmol·m^-2·s^-1,120μmol·m^-2·s^-1,160μmol·m^-2·s^-1,200μmol·m^-2·s^-1)on the growth,physiological and biochemical components of P.capillacea were studied to explore the suitable environmental conditions for the growth of P.capillacea.The results show that the suitable temperature range for growth is 19-28℃,the suitable salinity range is 25-35 psu,and the light intensity range is 80-200μmol·m^-2·s^-1.Based on the analysis of growth state,photosynthetic pigments synthesis and antioxidant capacity,P.capillacea is suitable to grow in the environment of high temperature,medium salinity and medium light intensity,and is suitable for cultivation and production in the southern sea area.（2）The optimal cultivation conditions of P.capillacea was explored by studying the synergistic effects of temperature（22℃,25℃,28℃）and salinity（25 psu,30 psu,35psu）on the growth and biochemical components of P.capillacea.The results show that under the optimized conditions of temperature 22℃,25℃and salinity 25 psu,30 psu,the growth of P.capillacea is faster,the synthesis of algal pigments content is at a higher level,and the antioxidant capacity is stronger.In this experiment,salinity is the main factor affecting the relative growth rate,photosynthetic pigments and malondialdehyde contents;The activity of total superoxide dismutase and the content of soluble sugar are more significantly affected by temperature.（3）In order to explore the response mechanism of high temperature stress of P.capillacea,the algae was treated at 35℃for 0 hour（control）,4 hours,8 hours,16 hours,24 hours,48 hours and 72 hours,related physiological and biochemical indexes were measured,and then the bioinformatics analysis of the mechanism of high temperature stress of P.capillacea was carried out by transcriptome sequencing technology.The results indicate that under the high temperature of 35℃,P.capillacea shows the adaptability of high temperature tolerance.At physiological level,the contents of malondialdehyde,proline,phycobiliprotein and the activity of total superoxide dismutase show significant changes.By analyzing the transcriptome sequencing results of Hsh-0h vs Hsh-8h and Hsh-0h vs Hsh-16h,the expression levels of 932 and 848genes significantly change respectively.The functional classification show that these differentially expressed genes are mainly involved in amino acid metabolism,photosynthesis,starch and sucrose metabolism,circadian rhythm and stress response.In this study,the suitable temperature,salinity and light intensity conditions were explored,which provided technical reference for cultivation,production and the development and utilization of P.capillacea.Through transcriptome sequencing analysis,the physiological response and molecular regulation mechanism of of P.capillacea under high temperature stress were preliminarily clarified,providing theoretical basis for high temperature resistance breeding.