title: Activities of principal photosynthetic enzymes in green macroalga Ulva linza: functional implication of C₄ pathway in CO₂ assimilation.
abstract: The green-tide-forming macroalga Ulva linza was profiled by transcriptome sequencing to ascertain whether the alga carries both C3 and C4 photosynthesis genes. The key enzymes involved in C4 metabolism including pyruvate orthophosphate dikinase (PPDK), phosphoenolpyruvate carboxylase (PEPC), and phosphoenolpyruvate carboxykinase (PCK) were found. When measured under normal and different stress conditions, expression of rbcL was higher under normal conditions and lower under the adverse conditions, whereas that of PPDK was higher under some adverse conditions, namely desiccation, high salinity, and low salinity. Both ribulose-1, 5-biphosphate carboxylase (RuBPCase) and PPDK were found to play a role in carbon fixation, with significantly higher PPDK activity across the stress conditions. These results suggest that elevated PPDK activity alters carbon metabolism in U. linza leading to partial operation of the C4 carbon metabolism, a pathway that, under stress conditions, probably contributes to the hardy character of U. linza and thus to its wide distribution.
authors.affiliation: Key Laboratory of Marine Bioactive Substance, The First Institute of Oceanography, State Oceanic Administration, Qingdao 266061, China.
authors.forename: Jianfang
authors.initials: J
authors.lastname: Xu
authors.forename: Xiaowen
authors.initials: X
authors.lastname: Zhang
authors.forename: Naihao
authors.initials: N
authors.lastname: Ye
authors.forename: Zhou
authors.initials: Z
authors.lastname: Zheng
authors.forename: Shanli
authors.initials: S
authors.lastname: Mou
authors.forename: Meitao
authors.initials: M
authors.lastname: Dong
authors.forename: Dong
authors.initials: D
authors.lastname: Xu
authors.forename: Jinlai
authors.initials: J
authors.lastname: Miao
mesh_terms: D053898:Biosynthetic Pathways; D057486:Carbon Cycle / Q000502:physiology*; D002245:Carbon Dioxide / Q000378:metabolism*; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects / Q000528:radiation effects; D018506:Gene Expression Regulation, Plant / Q000187:drug effects / Q000528:radiation effects; D008027:Light; D019764:Phosphoenolpyruvate Carboxykinase (ATP) / Q000235:genetics / Q000378:metabolism; D010730:Phosphoenolpyruvate Carboxylase / Q000235:genetics / Q000378:metabolism; D010788:Photosynthesis; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D011772:Pyruvate, Orthophosphate Dikinase / Q000235:genetics / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012273:Ribulose-Bisphosphate Carboxylase / Q000235:genetics / Q000378:metabolism; D054712:Salinity; D012965:Sodium Chloride / Q000494:pharmacology; D059467:Transcriptome / Q000187:drug effects / Q000528:radiation effects; D044445:Ulva / Q000201:enzymology* / Q000235:genetics / Q000502:physiology*; D014867:Water / Q000378:metabolism / Q000494:pharmacology
chemical_list: D010940:Plant Proteins; D014867:Water; D002245:Carbon Dioxide; D012965:Sodium Chloride; D011772:Pyruvate, Orthophosphate Dikinase; D010730:Phosphoenolpyruvate Carboxylase; C101625:RbcL protein, plastid; D012273:Ribulose-Bisphosphate Carboxylase; D019764:Phosphoenolpyruvate Carboxykinase (ATP)