Title : A novel protein interaction between RCI2s and PIP2;1 reducing water transport activity in Camelina under NaCl stress
Abiotic stresses are major limiting factors for crop growth and productivity. Plants show various adaptations to overcome or avoid abiotic stresses. Rare cold inducible 2 (RCI2) proteins are localized at the plasma membrane (PM) and are significantly induced by cold, salt, and drought stresses. The RCI2s are believed to enhance abiotic stress tolerance by regulating the membrane potential. Aquaporin PIP2 is a water transport channel protein that facilitates the transport of water, ions, and several solutes across the PM. The activity of PIP2s is regulated by phosphorylation of its N- and C-terminal residues. PIP2s are known to be important for water homeostasis under NaCl and drought stress. In this study, we focused on the functions of RCI2s and their interactions with aquaporin PIP2;1, which is important for cell water regulation under NaCl stress in the bioenergy crop Camelina sativa L. The characteristics of CsRCI2 proteins displayed high homology with RCI2-related proteins from various species. CsRCI2A/B/C/H proteins contained only two transmembrane domains (TMD) but CsRCI2D/E/F/G has both transmembrane domains and a C-terminal tail. Subcellular localization of the CsRCI2s encoded proteins were detected in the PM. The transcription level of CsRCI2A/B/E/F genes were induced by salinity stress at 150 mM NaCl, cold stress at 2?C, and 300 mM mannitol as osmotic stress. Protein accumulation of CsRCI2E and CsRCI2F were increased by NaCl concentrations but showed different accumulation level by intensity and duration of NaCl treatment. A bimolecular fluorescence complementation and co-immunoprecipitation test revealed interaction between CsRCI2E-CsPIP2 and CsRCI2F-CsPIP2. Moreover, co-expression of the four CsRCI2 proteins with CsPIP2;1 in Xenopus laevis oocytes reduced water transport activity and lessened current changes. Furthermore, the abundance of CsPIP2;1 protein was decreased under CsRCI2E and CsRCI2F co-expression. These results suggest that NaCl-induced expression of CsRCI2E and CsRCI2F contributes to the repression of CsPIP2;1, which may decrease Na+ ion transport and affect ion homeostasis.
Take Away Notes:
• Mechanism for abiotic stress tolerance in Camelina.
• Function of RCI2 proteins which related to abiotic stress tolerance.
• A physiological approach to compare abiotic stress tolerance.