Functional Differentiation of Chitin Oligosaccharides with Different Degrees of Polymerization in Salt-Stressed Wheat Seedlings
Anbang Li, Chang Liu, Boyun Qi, Hongwei Qiao, Yi Wang, Lubaihe Wei, Houxiang Wang, Minmin Hu, Ronge Xing, Song Liu, Kecheng LiAbstract
Soil salinity severely limits wheat growth and productivity, creating a need for sustainable strategies to improve salt tolerance. Chitin oligosaccharides are promising natural biostimulants, but their degree-of-polymerization (DP)-dependent functions remain unclear. Here, structurally defined chitin oligosaccharides (A2–A6) were individually applied to wheat seedlings exposed to 100 mM NaCl, and their effects were evaluated using growth, physiological, biochemical, transcriptomic, and metabolomic analyses. Results showed clear DP-dependent functional differentiation. A2 showed the strongest biomass-promoting effect, with fresh and dry weights 58.13% and 51.27% higher than those of A6-treated seedlings, respectively. In contrast, A6 exhibited stronger antioxidant capacity and ionic homeostasis regulation, with SOD and POD activities 25.84% and 42.33% higher than those of A2, and a 72.90% lower Na+/K+ ratio than in salt-stressed plants. Omics analyses revealed that A2 was primarily associated with growth-related metabolic adjustment, whereas A6 showed a stronger defense-oriented response involving MAPK signaling and plant hormone signal transduction. These findings demonstrate a DP-dependent trade-off between growth promotion and stress defense, providing insights into the functional specialization of chitin oligosaccharides in plant stress regulation.