Proteomic analysis of temperature dependency of buckwheat seed dormancy and quality degradation

Buckwheat is a functional staple food, which is rich in rutin and other flavonoids with strong antioxidant potential. However, the quality of buckwheat grain is easy to degrade during storage and low temperature is better to keep the flavor and texture. We tested the hypothesis that the quality degradation is related to seed dormancy which is lost at a rate in temperature-dependent manner in most seeds. To understand physiological processes in seeds under temperature stress, which affects quality of stored buckwheat grain, a gel-free/label-free proteomic analysis was conducted. Compared to the seeds before storage, a total of 30, 76, 52, 14, and 61 proteins were affected at 5 degrees C for 5 months, 5 degrees C for 10 months, 15 degrees C for 5 months, 15 degrees C for 10 months, and 25 degrees C for 5 months, respectively. Functional classification revealed that storage condition at 5 degrees C for 5 months resulted in different protein profile from other conditions and suitable for keeping best condition. Storage at higher temperature for longer time influenced proteins related to preparation for emergence by carbohydrate metabolism, endogenous gene expression, and protein homeostasis. Proteins such as granule-bound starch synthase and 13S seed storage protein consistently decreased in abundance during storage. These results suggest that stored buckwheat seeds experience seed dormancy release, but the processes are not clear in relation to temperature rise. Dormancy break is recognized but emergence is inhibited by abscisic acid, which was induced by temperature stress, showing the complexity of buckwheat germination control. The quality degradation of stored seeds might be due to changed starch composition and protein network.