Quantitative proteomics of Sesuvium portulacastrum leaves revealed that ion transportation by V-ATPase and sugar accumulation in chloroplast played crucial roles in halophyte salt tolerance.
Physiological and proteomic responses of Sesuvium portulacastrum leaves under salinity were investigated. Different from glycophytes, this halophyte had optimal growth at 200-300mM NaCl and accumulated more starch grains in chloroplasts under high salinity. Increased contents of soluble sugars, proline, and Na(+) were observed upon salinity. X-ray microanalysis revealed that Na(+) was mainly compartmentalized into cell vacuole. Quantitative proteomics produced 96 salt responsive proteins, and the majority was chloroplast-located proteins. Gene ontology analysis revealed that proteins involved in ion binding, proton transport, photosynthesis and ATP synthesis were overrepresented. The expressions of a Na(+)/H(+) antiporter and several ATP synthase subunits were activated upon high salinity. ATP hydrolysis assay demonstrated that V-ATPase activity at tonoplast was dramatically increased upon NaCl whereas vacuolar H(+)-pyrophosphatase and plasma membrane P-ATPase activities were not increased, which indicated that sodium compartmentalization was mainly performed by enhancing V-ATPase activity rather than P-ATPase and H(+)-pyrophosphatase. Accumulation of soluble sugars as well as sodium compartmentalization maintained the osmotic balance between vacuole and cytoplasm, which finally established ionic homeostasis in saline cells in true halophytes.


CONCLUSIONS
Physiological and proteomic analyses of S. portulacastrum leaves under different salinities were investigated. This true halophyte accumulated more soluble sugars, starch, proline and Na(+) under high salinity. Differential proteomics produced 96 salt responsive proteins and the majority was involved in ion binding, proton transport, photosynthesis, and ATP synthesis. A Na(+)/H(+) antiporter and several ATP synthase subunits were induced upon high salinity. ATP hydrolysis assay demonstrated that V-ATPase activity at tonoplast was dramatically increased whereas vacuolar H(+)-pyrophosphatase and plasma membrane ATPase activities were stable upon NaCl. These findings demonstrated that the increased Na(+) was compartmentalized into vacuole by enhancing V-ATPase activity rather than H(+)-ATPase.
Key Laboratory of Biology and Genetic Resources for Tropical Crops, Institute of Tropical Biosciences and Biotechnology, Chinese Academy of Tropical Agricultural Sciences, Haikou, Hainan 571101, China; Hainan University, Haikou, Hainan 570228, China.
Xiaoping
X
Yi
Key Laboratory of Biology and Genetic Resources for Tropical Crops, Institute of Tropical Biosciences and Biotechnology, Chinese Academy of Tropical Agricultural Sciences, Haikou, Hainan 571101, China.
Yong
Y
Sun
Key Laboratory of Biology and Genetic Resources for Tropical Crops, Institute of Tropical Biosciences and Biotechnology, Chinese Academy of Tropical Agricultural Sciences, Haikou, Hainan 571101, China.
Qian
Q
Yang
Key Laboratory of Biology and Genetic Resources for Tropical Crops, Institute of Tropical Biosciences and Biotechnology, Chinese Academy of Tropical Agricultural Sciences, Haikou, Hainan 571101, China; Hainan University, Haikou, Hainan 570228, China.
Anping
A
Guo
Key Laboratory of Biology and Genetic Resources for Tropical Crops, Institute of Tropical Biosciences and Biotechnology, Chinese Academy of Tropical Agricultural Sciences, Haikou, Hainan 571101, China; Hainan University, Haikou, Hainan 570228, China.
Lili
L
Chang
Key Laboratory of Biology and Genetic Resources for Tropical Crops, Institute of Tropical Biosciences and Biotechnology, Chinese Academy of Tropical Agricultural Sciences, Haikou, Hainan 571101, China.
Dan
D
Wang
Key Laboratory of Biology and Genetic Resources for Tropical Crops, Institute of Tropical Biosciences and Biotechnology, Chinese Academy of Tropical Agricultural Sciences, Haikou, Hainan 571101, China.
Zheng
Z
Tong
Key Laboratory of Biology and Genetic Resources for Tropical Crops, Institute of Tropical Biosciences and Biotechnology, Chinese Academy of Tropical Agricultural Sciences, Haikou, Hainan 571101, China.
Xiang
X
Jin
Key Laboratory of Biology and Genetic Resources for Tropical Crops, Institute of Tropical Biosciences and Biotechnology, Chinese Academy of Tropical Agricultural Sciences, Haikou, Hainan 571101, China.
Limin
L
Wang
AB SCIEX Asia Pacific Application Support Center, Shanghai 200233, China.
Jianlan
J
Yu
AB SCIEX Asia Pacific Application Support Center, Shanghai 200233, China.
Wenhai
W
Jin
AB SCIEX Asia Pacific Application Support Center, Shanghai 200233, China.
Yongming
Y
Xie
Key Laboratory of Biology and Genetic Resources for Tropical Crops, Institute of Tropical Biosciences and Biotechnology, Chinese Academy of Tropical Agricultural Sciences, Haikou, Hainan 571101, China; Hainan University, Haikou, Hainan 570228, China. Electronic address: xchwanghainan@163.com.
Xuchu
X
Wang
D035722:Aizoaceae / Q000201:enzymology*; D060365:Chloroplast Proteins / Q000096:biosynthesis*; D002736:Chloroplasts / Q000201:enzymology*; D015971:Gene Expression Regulation, Enzymologic / Q000502:physiology*; D018506:Gene Expression Regulation, Plant / Q000502:physiology*; D009997:Osmotic Pressure / Q000502:physiology*; D018515:Plant Leaves; D054712:Salinity; D025262:Vacuolar Proton-Translocating ATPases / Q000096:biosynthesis*
D060365:Chloroplast Proteins; D025262:Vacuolar Proton-Translocating ATPases
Halophyte; Ion transportation; Quantitative proteomics; Sesuvium portulacastrum; Sugar accumulation; Vacuolar ATPase