AUTHOR=Niu Citong , Wang Wenjun , Yao Haiqin , Liang Zhourui , Zhang Pengyan , Lu Xiaoping 

TITLE=Ascorbate−glutathione cycle involving in response of Bangia fuscopurpurea (Bangiales, Rhodophyta) to hyposalinity

JOURNAL=Frontiers in Marine Science

VOLUME=Volume 10 - 2023

YEAR=2023

URL=https://www.frontiersin.org/journals/marine-science/articles/10.3389/fmars.2023.1174472

DOI=10.3389/fmars.2023.1174472

ISSN=2296-7745

ABSTRACT=Bangia fuscopurpurea is an economic intertidal seaweed with a strong tolerance to hyposalinity. Little is known about the mechanism of this species adapting to hyposaline stress. Ascorbate-glutathione (AsA‒GSH) cycle plays important roles in many organisms under a variety of abiotic stresses. It was found here that under hyposalinities (15 and 0 psu), the contents of reduced glutathione (GSH), total glutathione (GSH+ oxidized glutathione, GSSG), cysteine, and the ratios GSH/GSSG and ascorbic acid (AsA)/dehydroascorbic acid (DHA) were significantly up-regulated; the activities of glutathione peroxidase (GPX), ascorbic acid peroxidase(APX) and monodehydroascorbate reductase (MDHAR) increased (p<0.05), and glutathione S-transferase (GST) activities decreased (p>0.05); the glutathione reductase (GR) activities decreased on the 1st day and recovered on the 5th day (p>0.05). The hyposalities-enhanced GSH/GSSG was weakened (still higher than control) while the GR activities were promoted by adding exogenous GSH and L-buthionine-sulfoximine (BSO). The hyposalities-enhanced GPX activities and AsA/DHA were strengthened by exogenous GSH but weakened by BSO. The dehydroascorbate reductase (DHAR) activities had no significant changes whether there was exogenous GSH or not, while DHAR activities together with DHA contents were enhanced by BSO under all salinities. The expression of APX gene markedly increased under hyposalinity+BSO treatment. Putative interaction proteins of APX were screened by yeast two hybrid system, including glutamate dehydrogenase 1a (glud 1a) and fructose diphosphate aldolase that function in stress resistance, and a light harvesting protein. The maximum quantum yield of photosystem II (Fv/Fm) of B. fuscopurpurea at 15 psu kept as high as the control level, which decreased to below the control level on the 1st day after adding GSH or BSO and then recovered on the 5th day. The results indicated that AsA‒GSH cycle played vital roles in response of B. fuscopurpurea to hyposalinity.