Molecular insights into the salt stress response of Pearl millet (Pennisetum glaucum): Pathways, differentially expressed genes and transcription factors

Introduction: Pearl millet (Pennisetum glaucum) plays a crucial role as a cereal crop in arid and semi-arid regions, where it confronts the formidable challenge of salt stress. Materials and Methods: To unravel the underlying molecular mechanisms that underpin its salt stress resilience, we subjected 14-day-old seedlings to three distinct groups: Control, 75 mM NaCl and 150 mM NaCl. These pots received daily irrigation with their respective treatment solutions for a duration of 7 days. Following this week-long treatment, we measured plant chlorophyll content, as well as the fresh and dry weights of shoots and roots. It became evident that the saline treatment, particularly in the 150 mM NaCl group, had a more pronounced impact on both weight and chlorophyll content in comparison to the control group, surpassing the effects observed in the 75 mM NaCl group. Subsequently, we conducted RNA sequence analysis on the leaves of Pearl millet from both the control and 150 mM NaCl-treated groups. Results: The results revealed that 27.6% of Pennisetum glaucum genes exhibited differential expression, with 3246 genes being upregulated and 7408 genes downregulated when compared to the control group. Principal component analysis underscored distinct variations in gene expression patterns between the control and salt-stressed groups. Pathway analysis sheds light on the upregulated differentially expressed genes (DEGs), highlighting their involvement in crucial pathways such as phytyl-PP biosynthesis, lysine degradation, glutamate biosynthesis, nitrate assimilation and DLO biosynthesis. Conversely, the downregulated DEGs were associated with pathways like coumarins biosynthesis, pinobanksin biosynthesis, UDP- d-glucuronate biosynthesis and cholesterol biosynthesis, among others. Furthermore, our transcription factor analysis unveiled specific families associated with the salt stress response, including bHLH, ERF, NAC, WRKY, bZIP, MYB and HD-ZIP. Conclusions: These findings represent a significant advancement in our comprehension of Pearl millet's capacity to withstand salt stress and provide potential targets for the development of salt-resistant crops, contributing to the advancement of sustainable agriculture in regions affected by salinity.