Effect of Overexpression of JERFs on Intracellular K+/Na+ Balance in Transgenic Poplar (Populus alba × P. berolinensis) Under Salt Stress

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.

Advances and Perspectives of Transgenic Technology and Biotechnological Application in Forest Trees

“…Interference with FDL expression enhanced the drought resistance of transgenic poplar (Yu et al, 2019). The K + /Na + homeostasis of root cells and tolerance to salt stress were improved in transgenic poplar overexpressing JERF36s (Ding et al, 2020). These studies provided insight into the mechanism of salt tolerance improvement in plants and will facilitate breeding strategies to improve salt tolerance.…”

Transcriptomic Analysis of Mature Transgenic Poplar Expressing the Transcription Factor JERF36 Gene in Two Different Environments

“…Whereas at Qiqihar, the DEGs from the ABJ01 vs. 9# comparison was mainly significantly enriched in Photosynthesis (28 DEGs), Oxidative phosphorylation (12 DEGs), and other pathways present in photosynthetic organisms. Studies have shown that overexpression of many ERF transcription factors, such as those found in poplar, soybean, tomato, wheat, and tobacco, result in stronger tolerance to abiotic and biotic stress by regulating the expression of stress-related genes ( Yao et al, 2016 ; Ku et al, 2018 ; Ding et al, 2020 ). This suggests that, compared with non-transgenic poplars, transgenic poplars mainly adapt to salt-alkali stress by regulating the expression of genes related to plant-pathogen interactions and photosynthesis.…”

“…Numerous studies have shown that the AP2/ERF family of transcription factors, which are found mainly in plants, play very important roles in regulating diverse environmental stress responses, such as abiotic stresses (cold, heat, drought, salinity, and osmotic stress) and biotic stresses (herbivorous insects and microbial pathogens) ( Feng et al, 2020 ). AP2/ERF transcription factors, such as JERF36 and ERF76 have the ability to enhance salt tolerance in transgenic poplar by increasing ABA and GA biosynthesis ( Li et al, 2009 ; Yao et al, 2016 ; Ding et al, 2020 ). DREB transcription factor, for example, SALTRESPONSIVE ERF1 (SERF1), can amplify and transmit salt-inducing signals through the MAPK cascade signaling pathway, leading to a response to salt stress in the plant ( Schmidt et al, 2013 ).…”

“…It is well known that, the AP2/ERF super-family of transcription factors also play important roles in hormonal regulation and plant development. Many studies have shown that AP2/ERF-type transcription factors can induce phytohormone responses, such as ethylene, ABA, and jasmonic acid, by activating target genes, other response factors, and even other AP2/ERF transcription factors to regulate various growth processes in plants ( Ding et al, 2020 ; Feng et al, 2020 ). In plants, MAPKs are activated mainly by stress-triggered secondary signals; for example, ABA and Ca + , rather than by the primary osmotic stress signal ( Zhu, 2016 ; Zhao et al, 2021 ).…”

“…Hybrid P. alba × P. berolinensis plants exhibit fast growth and a beautiful tree shape, and are widely used in urban greening and afforestation in the northeast, northwest, and north of China. Base on its susceptibility to salt stress, P. alba × P. berolinensis is difficult to grow in saline soils, which seriously affects its cultivation on saline-alkali land ( Ding et al, 2020 ). In the early stage of our research, we created an improved, salt-tolerant transgenic line of P. alba × P. berolinensis by overexpressing JERF 36, a gene from tomato that encodes a jasmonate/ethylene-responsive transcription factor ( Li et al, 2009 ; Zhang and Huang, 2010 ).…”