Abstract
Calcineurin B-like protein-interacting protein kinases (CIPKs) play essential roles in plant abiotic stress response. In order to better understand salt tolerance, we cloned and analyzed the NtCIPK9 gene from the halophyte Nitraria tangutorum. Phylogenetic analysis shows that NtCIPK9 belongs to a sister clade with the Arabidopsis AtCIPK9 gene and is thought to localize to the plasma membrane. NtCIPK9 shows the highest expression level in the Nitraria tangutorum root under normal growth conditions, whereas after NaCl treatment, the highest expression was found in the blade. NtCIPK9-overexpressing Arabidopsis plants have a higher seed germination rate, longer root length, and displayed higher salt tolerance than wild type seedlings under salt stress conditions. Furthermore, NtCIPK9 overexpression might enhance the expression of genes related to K+ transportation after NaCl treatment. Thus, we conclude that NtCIPK9 increases transgenic plant salt tolerance and reduces damage associated with salt stress by promoting the expression of genes controlling ion homeostasis. Our results suggest that NtCIPK9 could serve as an ideal candidate gene to genetically engineer salt-tolerant plants.
Highlights
Soil salinity gradually accumulates along with global environmental degradation and limits the quality and productivity of most important agricultural crops and trees worldwide (Mahajan and Tuteja, 2005; Zhou et al, 2014; Guo et al, 2018)
We found that overexpression of NtCIPK9 from Nitraria tangutorum in Arabidopsis increased seed germination rate under salt stress
The results suggested that the overexpression of NtCIPK9 might regulate the expression of potassium transporter AtHKT1 to promote the homeostasis of Na+ and K+ in Arabidopsis resistance for salt stress
Summary
Soil salinity gradually accumulates along with global environmental degradation and limits the quality and productivity of most important agricultural crops and trees worldwide (Mahajan and Tuteja, 2005; Zhou et al, 2014; Guo et al, 2018). Genetic engineering to improve the salt tolerance of crops has been actively investigated by plant scientists worldwide (Wang et al, 2003; Hu et al, 2005; Ashraf and Akram, 2009). Calcineurin B-like proteins (CBLs) and their targets CBLinteracting protein kinases (CIPKs) are involved in the Ca2+ signal pathway that functions during stress response (Kudla et al, 1999; Shi et al, 1999; Kim et al, 2000); they play important roles in maintaining cytoplasm ion homeostasis and improving salt tolerance. CIPKs contain a typical protein kinase domain with a putative activation loop and a unique C-terminal regulatory region with a conserved NAF/FISL motif, both of which are necessary and sufficient for the function of these genes (Shi et al, 1999; Albrecht et al, 2001; Guo et al, 2001). Studying how halophyte CIPKs homologs function might provide crucial perspective in addressing this question, as these genes could be functionally more efficient than their glycophyte counterparts (Himabindu et al, 2016)
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