Abstract
Salt stress is one of the main factors that affect both growth and development of plants. Maintaining K+/Na+ balance in the cytoplasm is important for metabolism as well as salt resistance in plants. In the present study, we monitored the growth (height and diameter) of transgenic Populus alba × P. berolinensis trees (ABJ01) carrying JERF36s gene (a tomato jasmonic/ethylene responsive factors gene) over 4 years, which showed faster growth and significant salt tolerance compared with non-transgenic poplar trees (9#). The expression of NHX1 and SOS1 genes that encode Na+/H+ antiporters in the vacuole and plasma membranes was measured in leaves under NaCl stress. Non-invasive micro-test techniques (NMT) were used to analyse ion flux of Na+, K+, and H+ in the root tip of seedlings under treatment with100 mM NaCl for 7, 15, and 30 days. Results showed that the expression of NHX1 and SOS1 was much higher in ABJ01 compared with 9#, and the Na+ efflux and H+ influx fluxes of root were remarkable higher in ABJ01 than in 9#, but K+ efflux exhibited lower level. All above suggest that salt stress induces NHX1 and SOS1 to a greater expression level in ABJ01, resulting in the accumulation of Na+/H+ antiporter to better maintain K+/Na+ balance in the cytoplasm of this enhanced salt resistant variety. This may help us to better understand the mechanism of transgenic poplars with improving salt tolerance by overexpressing JERF36s and could provide a basis for future breeding programs aimed at improving salt resistance in transgenic poplar.
Highlights
The total area of arid, semiarid and saline-alkali lands in China accounts for more than half of the total terrestrial with low underground water levels and serious salinization
The plant height of ABJ01 was 35.60% and 22.94% remarkably higher than 9# in 2006 and 2007, respectively, and the diameter of ABJ01 was 39.31% and 36.32% significantly higher than 9# in 2005 and 2006, respectively, under salt stress conditions (Figure 1), which indicated that the salt tolerance of ABJ01 was enhanced compared with 9#
The expression of NHX1 was nearly 4-fold higher in ABJ01 than in 9# under NaCl stress for 30 days. These results suggested that, mild stress can induce the expression of NHX1 in both ABJ01 and 9#, and with the increase of time, the higher expression of NHX1 can be effectively maintained in ABJ01 (Figure 5)
Summary
The total area of arid, semiarid and saline-alkali lands in China accounts for more than half of the total terrestrial with low underground water levels and serious salinization. K+/Na+ Balance in Transgenic Poplar toxicity, water shortage, and nutrient imbalances (Zhu, 2001; Kaleem et al, 2018; Liang et al, 2018; Yang and Guo, 2018; Chen et al, 2019). The prevalence and impact of high salinity on plant growth and productivity have drawn increasing attention (Widodo et al, 2009; Zhu et al, 2016; Yang and Guo, 2018). Soil salinization is an increasingly serious threat that limits poplar growth and afforestation program, so breeding salttolerant poplar has become very important and necessary
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