Physiological and Transcriptome Analysis Illuminates the Molecular Mechanisms of the Drought Resistance Improved by Alginate Oligosaccharides in Triticum aestivum L.

Alginate oligosaccharides (AOS) enhance drought resistance in wheat (Triticum aestivum L.), but the definite mechanisms remain largely unknown. The physiological and transcriptome responses of wheat seedlings treated with AOS were analyzed under drought stress simulated with polyethylene glycol-6000. The results showed that AOS promoted the growth of wheat seedlings and reduced oxidative damage by improving peroxidase and superoxide dismutase activities under drought stress. A total of 10,064 and 15,208 differentially expressed unigenes (DEGs) obtained from the AOS treatment and control samples at 24 and 72 h after dehydration, respectively, were mainly enriched in the biosynthesis of secondary metabolites (phenylpropanoid biosynthesis, flavonoid biosynthesis), carbohydrate metabolism (starch and sucrose metabolism, carbon fixation in photosynthetic organisms), lipid metabolism (fatty acid elongation, biosynthesis of unsaturated fatty acids, alpha-linolenic acid metabolism, cutin, suberine and wax biosynthesis), and signaling transduction pathways. The up-regulated genes were related to, for example, chlorophyll a-b binding protein, amylosynthease, phosphotransferase, peroxidase, phenylalanine ammonia lyase, flavone synthase, glutathione synthetase. Signaling molecules (including MAPK, plant hormones, H₂O₂ and calcium) and transcription factors (mainly including NAC, MYB, MYB-related, WRKY, bZIP family members) were involved in the AOS-induced wheat drought resistance. The results obtained in this study help underpin the mechanisms of wheat drought resistance improved by AOS, and provides a theoretical basis for the application of AOS as an environmentally sustainable biological method to improve drought resistance in agriculture.