Mixed-Oligosaccharides Promoted Seedling Growth of Direct-Seeded Rice under Salt and Alkaline Stress

Abstract

Rice direct seeding technology is an appealing alternative to traditional transplanting because it conserves workforces and irrigation. Nevertheless, there exist two main causes, salt and alkaline stress, which contribute to poor emergence and seedling growth and prevent the popularization and application of this technique in the Ningxia Region, China. Therefore, in order to prove if it is true that germination could be promoted by mixed-oligosaccharide (KP)-priming (seeds were soaked in KP solution before sowing) under salt and alkaline stress, a proteomics study was performed. KP-priming significantly mitigated abiotic stresses such as salt and alkaline inhibiting root elongation, ultimately improving seedling establishment. Through comparing the proteomics analyses, it is found that energy metabolic pathways are the vital factor of KP-priming, and the alleviation of salt and alkaline stress is explained. Key proteins, such as starch mobilization, pyruvate mobilization, and adenosine triphosphate (ATP) synthesis, are up-regulated by KP-priming, and then the salt and alkaline-triggered starch accumulation are significantly blocked, pyruvate metabolism enhanced. KP-priming also up-regulated ATP synthase to improve energy efficiency, thereby improving ATP formation. In addition, it enhanced antioxidant enzymatic activities and reduced the accumulation of reactive oxygen species. All of which help understand the energy regulatory pathways that are enhanced by KP-priming and mediate the promotion of growth under salt and alkaline conditions. Thus, this study demonstrates that KP-priming can improve rice seed germination under salt and alkaline stress through altering energy metabolism.