Proteome dynamics and physiological responses to short-term salt stress in <i>Leymus chinensis</i> leaves

<div><p>Salt stress is becoming an increasing threat to global agriculture. In this study, physiological and proteomics analysis were performed using a salt-tolerant grass species, <i>Leymus chinensis</i> (L. <i>chinensis</i>). The aim of this study is to understand the potential mechanism of salt tolerance in L. <i>chinensis</i> that used for crop molecular breeding. A series of short-term (<48 h) NaCl treatments (0 ~ 700 mM) were conducted. Physiological data indicated that the root and leaves growth were inhibited, chlorophyll contents decreased, while hydraulic conductivity, proline, sugar and sucrose were accumulated under salt stress. For proteomic analysis, we obtained 274 differentially expressed proteins in response to NaCl treatments. GO analysis revealed that 44 out of 274 proteins are involved in the biosynthesis of amino acids and carbon metabolism. Our findings suggested that L. <i>chinensis</i> copes with salt stress by stimulating the activities of POD, SOD and CAT enzymes, speeding up the reactions of later steps of citrate cycle, and synthesis of proline and sugar. In agreement with our physiological data, proteomic analysis also showed that salt stress depress the expression of photosystem relevant proteins, Calvin cycle, and chloroplast biosynthesis.</p></div

Statistical analysis on interactive effects of duration and concentration of NaCl treatments on parameters identified relating to growth development and carbon metabolites.

<p>Statistical analysis on interactive effects of duration and concentration of NaCl treatments on parameters identified relating to growth development and carbon metabolites.</p

Comparison on the contents of osmoprotectants and activities of POD, SOD and CAT enzymes between 400mM and 600mM NaCl.

<p>Student <i>t</i>-test was used to compare significant differences between 400mM and 600mM NaCl concentration, while symbol “*”, “***” represent <i>P</i> <0.05 and 0.001, respectively.</p

List of 44 proteins involving in carbon metabolism and biosynthesis of amino acids with differential expression in response to salt stress.

<p>Sensitivity represents the relative differences of proteins between 400mM and 600mM NaCl over 400mM NaCl, which is expressed as (A600-A400)/A400.</p

Classification of the patterns of dynamic response of 274 proteins to different NaCl concentrations.

<p>The colored panels represented the clusters enriched by significance, while black line in each panel represent the mean of expressed values of specific proteins in each group.</p

Dynamics response of relative hydraulic conductivity to a range of NaCl concentration for 24 hours and 48 hours in <i>Leymus chinensis</i>.

<p>Vertical bars represent mean values plus standard error values. Student <i>t</i>-test was used to compare significant differences between NaCl-treated duration of 24h and 48h, while symbol “*”, “**” represent P <0.05 and 0.01, respectively. At least 6 biological replicates were conducted.</p

Schematic diagram summarized from the expression of 44 proteins relating to biosynthesis of amino acids and carbon metabolism in response to salt stress.

<p>For clear illustration, the evented organelle or regions at cellular levels were separated, while the color of light orange, light green and light pink represent cytoplasm, chloroplast and mitochondria, respectively. The red arrow indicated the relatively expressed levels of each component in 600mM NaCl compared with 400mM from independently experimental measurements.</p

Dynamic response of root length and leaf length to a range of NaCl concentration for 24 hours and 48 hours in <i>Leymus chinensis</i>.

<p>Vertical bars represent mean values plus standard error values. Student <i>t</i>-test was used to compare significant differences between NaCl-treated duration of 24h and 48h, while symbol “*”, “**” represent P <0.05 and 0.01, respectively. At least 6 biological replicates were conducted.</p

KEGG pathway and enrichments analysis on 274 annotated proteins with differential expression across a range of NaCl treatments.

<p>The numbers and percentage of proteins with significant enrichments (A) and the list of each biological category (B). Numbers of proteins corresponding to different metabolism pathways (C).</p

Dynamic response of leaf-based chlorophyll content to a range of NaCl concentration for 24 hours and 48 hours in <i>Leymus chinensis</i>.

<p>Vertical bars represent mean values plus standard error values. Student <i>t</i>-test was used to compare significant differences between NaCl-treated duration of 24h and 48h, while symbol “*”, “**” represent P <0.05 and 0.01, respectively. At least 5 biological replicates were conducted.</p