Abstract
Salt stress dramatically reduces crop yield and quality, but the molecular mechanisms underlying salt tolerance remain largely unknown. To explore the wheat transcriptional response to salt stress, we performed high-throughput transcriptome sequencing of 10-day old wheat roots under normal condition and 6, 12, 24 and 48 h after salt stress (HASS) in both a salt-tolerant cultivar and salt-sensitive cultivar. The results demonstrated global gene expression reprogramming with 36,804 genes that were up- or down-regulated in wheat roots under at least one stress condition compared with the controls and revealed the specificity and complexity of the functional pathways between the two cultivars. Further analysis showed that substantial expression partitioning of homeologous wheat genes occurs when the plants are subjected to salt stress, accounting for approximately 63.9% (2,537) and 66.1% (2,624) of the homeologous genes in ‘Chinese Spring’ (CS) and ‘Qing Mai 6’ (QM). Interestingly, 143 salt-responsive genes have been duplicated and tandemly arrayed on chromosomes during wheat evolution and polyploidization events, and the expression patterns of 122 (122/143, 85.3%) tandem duplications diverged dynamically over the time-course of salinity exposure. In addition, constitutive expression or silencing of target genes in Arabidopsis and wheat further confirmed our high-confidence salt stress-responsive candidates.
Highlights
Another strategy for achieving enhanced salt tolerance, as excessive Na+ disrupts K+ uptake and cytosolic enzyme sensitivity10
It has been proposed that partitioning expression of the homeologous genes potentially accounts for the enhanced tolerance to abiotic stresses observed in polyploid plants; e.g., one copy of the alcohol dehydrogenase A gene (AdhA) responds to water submersion stress, whereas the other is up-regulated in cold conditions in allopolyploid cotton (Gossypium hirsutum
There was no difference in the leaf chlorophyll content after salt stress in either Qing Mai 6 (QM) or Chinese Spring (CS), a higher leaf chlorophyll content was found in QM compared with CS (Fig. 1B)
Summary
Another strategy for achieving enhanced salt tolerance, as excessive Na+ disrupts K+ uptake and cytosolic enzyme sensitivity10 It has been reported the regulation of low Na+ concentrations is primarily attributed to the activity of K+ and Na+ transporters and H+ pumps, and the SALT OVERLY SENSITIVE 2 (SOS2)-SOS3 protein kinase pathway, together with the Na+ transporter SOS1 drives the secretion and sequestration of toxic sodium ions in Arabidopsis cells. The growth of salt-tolerant plants should resume when subjected to salt stress, at a reduced rate This process is potentially involved in the control of hormones and cell division related genes. It has been proposed that partitioning expression of the homeologous genes potentially accounts for the enhanced tolerance to abiotic stresses observed in polyploid plants; e.g., one copy of the alcohol dehydrogenase A gene (AdhA) responds to water submersion stress, whereas the other is up-regulated in cold conditions in allopolyploid cotton (Gossypium hirsutum). Given that allohexaploid wheat contains three subgenomes, we attempt to determine the expression partitioning of homeologs in response to salinity exposure over time
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