الملخص الإنجليزي
The global agriculture systems are under tremendous pressure of abiotic stresses due to climate change. In order to meet the food demands of the increasing population, there is a need to develop sustainable agriculture by increasing the ability of plants to tolerate stress conditions. In Oman, date palm cultivation is a prime agricultural activity which contributes to over 355 metric tonnes dates annually. However, due to the improper irrigation and agriculture practices, the soil salinity along the coast has increased over the past few years. Date palm is a relative salinity stress-tolerant plant however, soil salinity has affected the productivity, quality and the health of the plants. Therefore, the aim of this project was to study the salinity tolerance traits in date palm using a transcriptomic and functional gene analysis approach. The study was initiated by global transcriptome analysis of salinity stressed and non-stressed leaf and root tissues of the seedlings. The gene expression profiles revealed a pattern of differentially expressed genes under salt stress, it was observed that 2630 and 4687 genes were differentially expressed in leaves and roots tissues, respectively. The transcriptome study also identified the genes and the pathways that are associated with salinity and thus provided a foundation for functional characterization of salt stress-responsive genes in date palm. In order to confirm the gene expression results obtained using the total RNA-sequencing method, quantitative real-time PCR (qPCR) was performed using reference genes that were experimentally identified in this study. Further to functionally identify salinity stress-responsive genes, a whole cDNA library of salinity stressed date palm root was screened using a yeast bio-assay. The yeast functional screening bioassay was able to identify date palm 47 genes that could potentially play a role in salinity tolerance in plants. Two important genes identified from the yeast assay; plasma membrane intrinsic 1;2 (PdPIP1;2) and metallothionein 2A (PdMT2A) were selected for functional characterization in planta using Arabidopsis thaliana as a model plant. The heterologous overexpression of PdPIP1;2 in Arabidopsis improved drought and salinity tolerance by maintaining a balanced K+/Na+ ratio, water content and chlorophyll content in transgenic plants. In addition, PdPIP1;2 also improved the vigor and survival capacity of the recovered drought-stressed transgenic plants. The transgenic plants overexpressing PdMT2A accumulated less Na+ maintained high K+/Na+ ratio, better chlorophyll content, and higher superoxide dismutase (SOD) activity and showed better survival capacity during drought and salinity stress. Finally, the outcomes of this study may open a new direction in producing drought- and salt-tolerant date palm using conventional and unconventional biotechnological tools.
