Abstract
Date palm regards as a valuable genomic resource for exploring the tolerance genes due to its ability to survive under the sever condition. Although a large number of differentiated genes were identified in date palm responding to salt stress, the genome-wide study of alternative splicing (AS) landscape under salt stress conditions remains unknown. In the current study, we identified the stress-related genes through transcriptomic analysis to characterize their function under salt. A total of 17,169 genes were differentially expressed under salt stress conditions. Gene expression analysis confirmed that the salt overly sensitive (SOS) pathway genes, such as PdSOS2;1, PdSOS2;2, PdSOS4, PdSOS5, and PdCIPK11 were involved in the regulation of salt response in date palm, which is consistent with the physiological analysis that high salinity affected the Na+/K+ homeostasis and amino acid profile of date palm resulted in the inhibition of plant growth. Interestingly, the pathway of “spliceosome” was enriched in the category of upregulation, indicating their potential role of AS in date palm response to salt stress. Expectedly, many differentially alternative splicing (DAS) events were found under salt stress conditions, and some splicing factors, such as PdRS40, PdRSZ21, PdSR45a, and PdU2Af genes were abnormally spliced under salt, suggesting that AS-related proteins might participated in regulating the salt stress pathway. Moreover, the number of differentially DAS-specific genes was gradually decreased, while the number of differentially expressed gene (DEG)-specific genes was increased with prolonged salt stress treatment, suggesting that AS and gene expression could be distinctively regulated in response to salt stress. Therefore, our study highlighted the pivotal role of AS in the regulation of salt stress and provided novel insights for enhancing the resistance to salt in date palm.
Highlights
Date palm (Phoenix dactylifera L.) is an important fruit crop in several arid and semiarid countries in North Africa, the Middle East, and Central America
It was found that the content of H2O2 was highly accumulated for 5 days, and decreased with prolonged salt stress treatment, and the activities of SOD and POD were increased in response to salt stress, implying that plants could alleviate the damage of membrane integrity via oxidizing membrane lipids that were triggered by reactive oxygen species (ROS) (Supplementary Figure 1B)
These results demonstrated that the high salinity inhibits plant growth by disequilibrating the K+/Na+ homeostasis in date palm
Summary
Date palm (Phoenix dactylifera L.) is an important fruit crop in several arid and semiarid countries in North Africa, the Middle East, and Central America. The date palm trees have the ability to grow under the severer climatic conditions, such as very hot and dry climates, and even in close proximity to the seashore that contained large amounts of salty and alkaline soils (Yaish and Kumar, 2015). The date palm trees were supposed to be drought- and salt-tolerant plants and have evolved a series of mechanism for their adaptation. A high level of salt results in severe soil problems, and high salinity in soil impairs the growth due to the toxicity of Na+ and other ions (Shrivastava and Kumar, 2015). Plants have evolved several adaptations to deal with high salinity by regulating the ion influx and efflux at the plasma membrane, ion compartmentation in vacuoles, and maintaining the osmotic balance (van Zelm et al, 2020). In addition to trigger this cellular adaptation, expressions of many stress-responsive genes, such as ionic transporters, transcription factors, and protein kinases have been regulated by salt stress (Zhu, 2016; Yang and Guo, 2018b; Zhang et al, 2021)
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