Abstract
Salinity is a major abiotic stress that limits maize yield and quality throughout the world. We investigated phosphoproteomics differences between a salt-tolerant inbred line (Zheng58) and a salt-sensitive inbred line (Chang7-2) in response to short-term salt stress using label-free quantitation. A total of 9448 unique phosphorylation sites from 4116 phosphoproteins in roots and shoots of Zheng58 and Chang7-2 were identified. A total of 209 and 243 differentially regulated phosphoproteins (DRPPs) in response to NaCl treatment were detected in roots and shoots, respectively. Functional analysis of these DRPPs showed that they were involved in carbon metabolism, glutathione metabolism, transport, and signal transduction. Among these phosphoproteins, the expression of 6-phosphogluconate dehydrogenase 2, pyruvate dehydrogenase, phosphoenolpyruvate carboxykinase, glutamate decarboxylase, glutamate synthase, l-gulonolactone oxidase-like, potassium channel AKT1, high-affinity potassium transporter, sodium/hydrogen exchanger, and calcium/proton exchanger CAX1-like protein were significantly regulated in roots, while phosphoenolpyruvate carboxylase 1, phosphoenolpyruvate carboxykinase, sodium/hydrogen exchanger, plasma membrane intrinsic protein 2, glutathione transferases, and abscisic acid-insensitive 5-like protein were significantly regulated in shoots. Zheng58 may activate carbon metabolism, glutathione and ascorbic acid metabolism, potassium and sodium transportation, and the accumulation of glutamate to enhance its salt tolerance. Our results help to elucidate the mechanisms of salt response in maize seedlings. They also provide a basis for further study of the mechanism underlying salt response and tolerance in maize and other crops.
Highlights
Salt stress is a major factor that limits plant growth and development throughout the world
The phosphorylation of Phosphoenolpyruvate carboxylase 1 (PEP1) was decreased in both inbred lines at 0.5 h of salt treatment and significantly increased at 2 h; the increase was greater in Zheng58 than in Chang7-2 (6.46-fold versus 4.72-fold); in Zheng58, carbon metabolism was enhanced to produce more energy for salt stress relief
We explored the mechanism of salt tolerance in maize by comparing differentially regulated phosphoproteins in the maize inbred lines Chang7-2 and Zheng58 under short-term salt stress
Summary
Salt stress is a major factor that limits plant growth and development throughout the world. Increased salt concentrations in plant roots and shoots cause ion toxicity, hyperosmotic stress, and oxidative damage, impair metabolic processes, and decrease photosynthetic efficiency in crops [2,3]. One mechanism that alleviates salt stress involves removal of sodium (Na+) from the cytoplasm by transporting Na+ into the vacuole or out of the cell [4]. Salt stress leads to the production of reactive oxygen species (ROS) in mitochondria, chloroplasts, and peroxisomes in plants, which causes oxidative damage to proteins, DNA, and lipids [8]. Elimination of excessive ROS via the glutathione–ascorbate cycle and maintaining tolerable salt levels inside the plant cells through exportation or compartmentalization are generally accepted as two major strategies used by plants to survive salinity stress [9]. It is reported that plants can synthesize and accumulate small molecules, such as proline, betaine, soluble sugars, and amino acids, to protect themselves from salt stress [10,11,12]
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