Abstract
Understanding molecular mechanisms underlying plant salinity tolerance provides valuable knowledgebase for effective crop improvement through genetic engineering. Current proteomic technologies, which support reliable and high-throughput analyses, have been broadly used for exploring sophisticated molecular networks in plants. In the current study, we compared phosphoproteomic and proteomic changes in roots of different soybean seedlings of a salt-tolerant cultivar (Wenfeng07) and a salt-sensitive cultivar (Union85140) induced by salt stress. The root samples of Wenfeng07 and Union85140 at three-trifoliate stage were collected at 0 h, 0.5 h, 1 h, 4 h, 12 h, 24 h, and 48 h after been treated with 150 mm NaCl. LC-MS/MS based phosphoproteomic analysis of these samples identified a total of 2692 phosphoproteins and 5509 phosphorylation sites. Of these, 2344 phosphoproteins containing 3744 phosphorylation sites were quantitatively analyzed. Our results showed that 1163 phosphorylation sites were differentially phosphorylated in the two compared cultivars. Among them, 10 MYB/MYB transcription factor like proteins were identified with fluctuating phosphorylation modifications at different time points, indicating that their crucial roles in regulating flavonol accumulation might be mediated by phosphorylated modifications. In addition, the protein expression profiles of these two cultivars were compared using LC MS/MS based shotgun proteomic analysis, and expression pattern of all the 89 differentially expressed proteins were independently confirmed by qRT-PCR. Interestingly, the enzymes involved in chalcone metabolic pathway exhibited positive correlations with salt tolerance. We confirmed the functional relevance of chalcone synthase, chalcone isomerase, and cytochrome P450 monooxygenase genes using soybean composites and Arabidopsis thaliana mutants, and found that their salt tolerance were positively regulated by chalcone synthase, but was negatively regulated by chalcone isomerase and cytochrome P450 monooxygenase. A novel salt tolerance pathway involving chalcone metabolism, mostly mediated by phosphorylated MYB transcription factors, was proposed based on our findings. (The mass spectrometry raw data are available via ProteomeXchange with identifier PXD002856).
Highlights
From the ‡College of Life and Environmental Sciences, Hangzhou Normal University, Hangzhou, Zhejiang, 310036, PR China; §Shanghai Applied Protein Technology Co
Plants have evolved a series of adaptive mechanisms to sense and respond to salinity cues and these include active involvements of multiple phosphorylation cascades, such as salt overly sensitive (SOS) pathway, phosphatidic acid (PA)-mediated activation of calcium-dependent protein kinase (CDPK), abscisic acid (ABA)-regulated activation of mitogen-activated protein kinase (MAPK) cascades [11,12,13,14]
After NaCl treatment, we found that the relative contents of chlorophyll a, b, and carotenoids in Union85140 decreased more than that in Wenfeng07 (Fig. 2)
Summary
From the ‡College of Life and Environmental Sciences, Hangzhou Normal University, Hangzhou, Zhejiang, 310036, PR China; §Shanghai Applied Protein Technology Co. Soybean Roots’ Tolerances to Salinity 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 [10]. Major high throughput strategies including transcriptomic, proteomic, and metabolomic approaches, have been used to dissect the responses of soybean root to salinity stress [17,18,19,20,21]. Most of these studies were focused on relatively late responses to salinity (e.g. over 48 h after Naϩ treatment), earlier signal events minutes after the treatments were apparently ignored. The TiO2 affinity chromatography has been generally accepted as one of the most effective approaches in enrichment of phosphopeptides [26]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
