Abstract
Salt stress is one of the key abiotic stresses that causes great loss of yield and serious decrease in quality in maize (Zea mays L.). Therefore, it is very important to reveal the molecular mechanism of salt tolerance in maize. To acknowledge the molecular mechanisms underlying maize salt tolerance, two maize inbred lines, including salt-tolerant 8723 and salt-sensitive P138, were used in this study. Comparative proteomics of seedling roots from two maize inbred lines under 180 mM salt stress for 10 days were performed by the isobaric tags for relative and absolute quantitation (iTRAQ) approach. A total of 1056 differentially expressed proteins (DEPs) were identified. In total, 626 DEPs were identified in line 8723 under salt stress, among them, 378 up-regulated and 248 down-regulated. There were 473 DEPs identified in P138, of which 212 were up-regulated and 261 were down-regulated. Venn diagram analysis showed that 17 DEPs were up-regulated and 12 DEPs were down-regulated in the two inbred lines. In addition, 8 DEPs were up-regulated in line 8723 but down-regulated in P138, 6 DEPs were down-regulated in line 8723 but up-regulated in P138. In salt-stressed 8723, the DEPs were primarily associated with phenylpropanoid biosynthesis, starch and sucrose metabolism, and the mitogen-activated protein kinase (MAPK) signaling pathway. Intriguingly, the DEPs were only associated with the nitrogen metabolism pathway in P138. Compared to P138, the root response to salt stress in 8723 could maintain stronger water retention capacity, osmotic regulation ability, synergistic effects of antioxidant enzymes, energy supply capacity, signal transduction, ammonia detoxification ability, lipid metabolism, and nucleic acid synthesis. Based on the proteome sequencing information, changes of 8 DEPs abundance were related to the corresponding mRNA levels by quantitative real-time PCR (qRT-PCR). Our results from this study may elucidate some details of salt tolerance mechanisms and salt tolerance breeding of maize.
Highlights
Salinity is one of the increasingly serious environmental and ecological problems, which threatens the limited soil resources on which human beings depend [1], and poses a major constraint on the sustainability of crop yields [2]
Relative electrolyte leakage (REL), relative water content (RWC), root activity (RA), malondialdehyde (MDA) content, proline (Pro) content, superoxide dismutase (SOD) activity, peroxidase (POD) activity and catalase (CAT) activity were used as indexes to evaluate the salt tolerance of two varieties under salt stress
The results showed that the inhibition degree of salt stress on maize growth was related to the characteristics of the maize plant itself
Summary
Salinity is one of the increasingly serious environmental and ecological problems, which threatens the limited soil resources on which human beings depend [1], and poses a major constraint on the sustainability of crop yields [2]. How to maximize the use of this saline-alkaline land and reduce agricultural losses have become some of the most important tasks in the development of agricultural production. Many plant salt tolerance genes have been identified by transcriptome analysis, such as OsNHX1 [5] and OsHKT7 [6]. These data are useful for better understanding the mechanism of salt tolerance in plants, even though the expression level of mRNA does not directly correspond to protein abundance [7]. The isobaric tags for relative and absolute quantitation (iTRAQ) has been used to study the proteomic characteristics and salt stress response proteins of plants [9,10]
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