Involvement of cell cycle and ion transferring in the salt stress responses of alfalfa varieties at different development stages

Abstract

Background Alfalfa (Medicago sativa) is the worldwide major feed crop for livestock. However, forage quality and productivity are reduced by salt stress, which is a common issue in alfalfa-growing regions. The relative salt tolerance is changed during plant life cycle. This research aimed to investigate the relative salt tolerance and the underlying mechanisms of two alfalfa varieties at different developmental stages. Results Two alfalfa varieties, "Zhongmu No.1 (ZM1)" and "D4V", with varying salt tolerance, were subjected to salt stress (0, 100, 150 mM NaCl). When the germinated seeds were exposed to salt stress, D4V exhibited enhanced primary root growth compared to ZM1 due to the maintenance of meristem size, sustained or increased expression of cell cycle-related genes, greater activity of antioxidant enzymes and higher level of IAA. These findings indicated that D4V was more tolerant than ZM1 at early developmental stage. However, when young seedlings were exposed to salt stress, ZM1 displayed a lighter wilted phenotype and leaf cell death, higher biomass and nutritional quality, lower relative electrolytic leakage (EL) and malondialdehyde (MDA) concentration. In addition, ZM1 obtained a greater antioxidant capacity in leaves, indicated by less accumulation of hydrogen peroxide (H2O2) and higher activity of antioxidant enzymes. Further ionic tissue-distribution analysis identified that ZM1 accumulated less Na+ and more K+ in leaves and stems, resulting in lower Na+/K+ ratio, because of possessing higher expression of ion transporters and sensitivity of stomata closure. Therefore, the relative salt tolerance of ZM1 and D4V was reversed at young seedling stages, with the young seedlings of the former being more salt-tolerant. Conclusion Our data revealed the changes of relative order of salt tolerance between alfalfa varieties as they develop. Meristem activity in primary root tips and ion transferring at young seedling stages were underlying mechanisms that resulted in differences in salt tolerance at different developmental stages.

NO enhances the adaptability to high-salt environments by regulating osmotic balance, antioxidant defense, and ion homeostasis in eelgrass based on transcriptome and metabolome analysis

“…4.2 Conjoint analysis to explore the role of NO in adapting to high-salinity marine environment in stems of eelgrass Maintaining intracellular ion homeostasis is an essential feature for plants to adapt to high-salt environments. When plants are exposed to high-salt environments, excessive accumulation of harmful ions (such as Na + ) in cells will affect normal metabolic activities, such as the absorption of other ions (such as K + ), resulting in an imbalance of ion homeostasis (Yin et al, 2023). In this study, the expression levels of genes such as ABC transporter B family member 21 (Zosma06g17130), zinc transporter (ZTP) (Zosma01g21230), zinc transporter ZTP29 (Zosma05g21520), and manganese transport protein MntH (Zosma01g35590) (Supplementary Table 3) in ABC transporter, zinc ion transmembrane transporter, and iron ion transporter pathways in the stems were significantly downregulated after inhibiting NO synthesis (Figures 2C, D).…”