Establishment And Development Induction Of Filaments In Scytosiphon Lomentaria

Scytosiphon lomentaria is an edible brown macroalga globally distributed around the temperate and cold coastal areas.Developing the cultivation of S.lomentaria could significantly contribute to the seaweed aquaculture and compensate for its shortcoming,i.e.,the fewer cultivated species and the monoculture products.In addition,the mechanism underlying the direct induction of filaments to form seedlings is not clarified.In this paper,the techniques of filaments-derived seedling and life history is systematically elaborated by the in-door and in-situ cultivation with S.lomentaria.Furthermore,the combination of transcriptomic and metabolomic techniques revealed a light and temperature induced mechanism of filaments development at the phenotypic,physiological and genetic levels.The main results showed as following:1.Establishment and application of S.lomentaria filaments.The technique of filaments-derived seedling has the advantages of simplicity,high stability and low-energy consumption,which is considered to be the potential strategy for the future large-scale cultivation of S.lomentaria.However,the method still has some challenges,such as slowly amplified filaments,weak and uneven attachment,etc.In this paper,the technique was improved by studying the establishment,amplification culture,development induction,and seedling breeding of filaments.The results were as follows:successful establishment of uncontaminated germplasm through aseptic treatment of the mature thalli,isolation and culture of filaments and regular dipping in antibiotics;continuous aerated culture after fragmentation of clustered filaments into single-columns achieves faster amplification rates,with an average weight gain of 2.3 times that of normal culture;the filaments are induced to develop to the cell enlargement stage,and then evenly sprayed to the culture collectors after being dissociated into 3-5 cell size,which can effectively address the problem of poor and uneven attachment;sea farming of S.lomentaria by floating raft method.In addition,it was confirmed that the mature thalli produce filamentous and crustose thalli through sexual reproduction,and both of them can directly germinate seedlings.Totally,this paper perfected the technique of filaments-derived seedling and life history of S.lomentaria.2.Light-temperature induction mechanism of filaments development in S.lomentaria.The direct development of S.lomentaria filaments into seedlings by environmental signals induction is the primary seedling breeding technique,yet the induction mechanism of filaments in response to environmental signals is elusive.This paper investigates the effects of lowering temperature(LT),shortening daylight(SD)and dual-signal(DS)induction treatment on filaments development at three levels: phenotypic changes,phytohormone regulation and gene expression profiles.Compared to the SD in which only enlarged filamentous cells developed,the cell enlarged rate was faster and seedlings appeared sequentially after one week in the DS and SD.Phytohormone assays showed that1-Aminocyclopropanecarboxylic acid(ACC)and Gibberellin A9(GA9)levels increased in all treatments,while Indole-3-acetic acid(IAA)decreased and was more significant in LT and DS;Gibberellin A1(GA1)levels continued to increase in LT and DS,and Abscisic Acid(ABA)was only detected in samples induced for one week in both treatments.Further,the expression of genes encoding key enzymes for ABA,GA,Auxin,and ethylene synthesis was generally consistent with phytohormone levels and corresponding signaling pathways were activated.Conclusively,SD and LT may regulate filamentous cell enlargements and seedling growth by combined promotion of ACC and GA1 signaling as well as inhibition of IAA,whereas LT also activates GA9 and ABA to induce seedling emergence.