Abstract
Although cell wall polymers play important roles in the tolerance of plants to abiotic stress, the effects of salinity on cell wall composition and metabolism in grasses remain largely unexplored. Here, we conducted an in-depth study of changes in cell wall composition and phenolic metabolism induced upon salinity in maize seedlings and plants. Cell wall characterization revealed that salt stress modulated the deposition of cellulose, matrix polysaccharides and lignin. The extraction and analysis of arabinoxylans by size-exclusion chromatography, two-dimensional NMR spectroscopy and carbohydrate gel electrophoresis showed a reduction of arabinoxylan content in salt-stressed roots, with no changes in xylose/arabinose ratios. Saponification and mild acid hydrolysis followed by RP-HPLC analysis revealed that salt stress also reduced the feruloylation of arabinoxylans. Determination of lignin content and composition by nitrobenzene oxidation and two-dimensional NMR confirmed the increased incorporation of syringyl units in lignin polymer. Our data also revealed the induction of the expression of genes and enzymes enrolled in phenylpropanoid biosynthesis under salinity. The UPLC-MS-based metabolite profiling confirmed the modulation of phenolic profiling by salinity and the accumulation of ferulate and its derivatives 3- and 4-O-feruloyl quinate. In conclusion, we present a model for explaining cell wall remodeling in response to salinity.
Highlights
Soil salinity is an important environmental problem for more than 800 million hectares of land, which are affected by either salinity (397 million ha) or sodicity (434 million ha) (Munns and Tester, 2008)
We examined whether salt stress led to a reduced abundance of AX or the chain length of AX molecules using size-exclusion chromatography coupled to a multi-angle light scattering detector (SEC-multi-angle light-scattering (MALS)) of 1 M and 4 M KOH xylan-enriched fractions (Fig. 2b)
The content of FA esterified to AX followed the same modulation pattern as found for total ester-linked FA: salt exposure decreased the FA levels in studied the roots (S-roots) and plant roots by 38% and 50%, respectively (Fig. 4c), albeit an 82% increase was observed in stems, and no significant difference was observed in leaves
Summary
Soil salinity is an important environmental problem for more than 800 million hectares of land (ca. 6% of the world’s total land), which are affected by either salinity (397 million ha) or sodicity (434 million ha) (Munns and Tester, 2008). The amount of crystalline cellulose measured by the anthrone-sulfuric acid method in AIR of plant roots and stems was significantly reduced (–11% and –29%, respectively) upon salt stress, while that of S-roots and leaves was similar to that of the corresponding controls (Fig. 1d).
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