Key message: Salt stress triggers a simultaneous transcriptional repression and aquaporin internalization to modify root cell water conductivity. Abstract: Plasma membrane intrinsic proteins (PIPs) are involved in the adjustment of plant water balance in response to changing environmental conditions. In this study, Arabidopsis wild-type (Col-0) and transgenic lines overexpressing PIP2;7 were used to investigate and compare their response to salt stress. Hydraulic conductivity measurements using a high-pressure flowmeter (HPFM) revealed that overexpression of PIP2;7 induced a sixfold increase in root hydraulic conductivity of four week-old Arabidopsis thaliana plants compared to WT. Exposure to a high salt stress (150 mM NaCl) triggered a rapid repression of overall aquaporin activity in both genotypes. Response to salt stress was also investigated in 8 day-old seedlings. Exposure to salt led to a repression of PIP2;7 promoter activity and a significant decrease in PIP2;7 mRNA abundance within 2 h. Concomitantly, a rapid internalization of fluorescently-tagged PIP2;7 proteins was observed but removal from the cell membrane was not accompanied by further degradation of the protein within 4 h of exposure to salinity stress. These data suggest that PIP transcriptional repression and channel internalization act in concert during salt stress conditions to modulate aquaporin activity, thereby significantly altering the plant hydraulic parameters in the short term.
Bibliographical noteFunding Information:
We thank Ewelina Grzeskiewicz for her help in this work and Frank Van Breusegem (PSB, VIB, Ghent) for lending the Licor infrared gas-exchange system. Confocal microscopy was carried out at the UCL imaging platform IMABIOL. This work was supported by grants from the Belgian National Fund for Scientific Research (FNRS), the Interuniversity Attraction Poles Programme-Belgian Science Policy (IAP7/29), the Belgian French community ARC11/16???036 project and the Bauchau Award. A. P. was supported by an UCL Incoming post-doctoral Fellowship co-funded by the Marie Curie Actions of the European Commission. C.H. was a FNRS postdoctoral researcher. T.M. was a research fellow at the Fonds de Formation ?? la Recherche dans l'Industrie et l'Agriculture. Alicia Pou: Conception and design, Acquisition of data, Analysis and interpretation of data, Drafting and revising the article. Linda Jeanguenin: Acquisition of data, Analysis and interpretation of data, Drafting and revising the article. Thomas Milhiet: Acquisition of data, Analysis and interpretation of data. Henri Batoko: Drafting and revising the article. Fran??ois Chaumont: Conception and design, Analysis and interpretation of data, Drafting and revising the article. Charles Hachez: Conception and design, Acquisition of data, Analysis and interpretation of data, Drafting and revising the article.
- Plasma membrane
- Root hydraulic conductivity
- Salt stress
- Water relation