Populus euphratica PeREM6.5 regulating tolerance mechanism to water stress in Arabidopsis thaliana

  Objective  Remorin is a protein family commonly found in bryophytes, gymnosperms and angiosperms, and plays an important role in regulating plant growth, development, and the response to biotic stress. The physiological mechanism of remorin in plant adapting to abiotic stress has rarely been investigated. We have previously shown that PeREM6.5, a remorin protein originated from stress-resistant Populus euphratica, increased salt tolerance through enhancing activity of plasma membrane (PM) H⁺-ATPase. The role of PeREM6.5 in water stress tolerance was investigated in this study. The aim is to elucidate the physiological and molecular mechanism underlying PeREM6.5 in plant adaptation to drought stress.

  Method  The PeREM6.5-overexpressed Arabidopsis thaliana (OE1 and OE2), wildtype (WT), and vecter control (VC) were used in this study. These four genotypes of A. thaliana were treated with osmotic stress, soil drought and rehydration, respectively. The PeREM6.5-regulated drought response was evaluated at the physiological, biochemical and molecular levels.

  Result  Under mannitol treatment, the seed survival rate and root length of PeREM6.5-overexpressed Arabidopsis thaliana were significantly higher than WT and VC, and the cell membrane was less damaged by osmotic stress. The phenotypic differences were mainly related to the enhanced ability for water uptake and antioxidant defence in the transgenic plants. The expression of water channel genes, AtPIP1;2 and AtPIP2;1 was upregulated by osmotic treatment in PeREM6.5-transgenic lines. Mannitol treatment induced the accumulation of H₂O₂, causing oxidative damage to the cell membrane in WT and VC. PeREM6.5-transgenic plants up-regulated the transcription of antioxidant enzyme genes, POD and CAT after mannitol treatment. The high activities of POD and CAT could eliminate H₂O₂, and thus reduce the membrane damage caused by reactive oxygen species. After 9 d of drought treatment, the decrease of chlorophyll content in soil-cultured transgenic lines was lower than that of non-transgenic lines. After rehydration, the recovery of chlorophyll content in transgenic plants was higher than WT and VC. Moreover, PeREM6.5-transgenic plants exhibited a higher ability to maintain PSⅡ actual photosynthetic quantum yield under drought. These results indicated that the overexpression of PeREM6.5 improved the plant capacity to tolerate water stress.

  Conclusion  The above results indicate that the overexpression of PeREM6.5 gene enhances the tolerance to water stress in Arabidopsis thaliana plants.