Exogenous application of phytosulfokine α (PSKα) delays yellowing and preserves nutritional quality of broccoli florets during cold storage

In this study, we tested the exogenous application of phytosulfokine alpha (PSK alpha) for delaying the yellowing of broccoli florets during cold storage. Our results showed that the lower yellowing in broccoli florets treated with 150 nM PSK alpha was probably due to the higher endogenous accumulation of PSK alpha, leading to the endogenous accumulation of guanosine 3', 5'-cyclic monophosphate (cGMP). Besides, broccoli florets treated with 150 nM PSK alpha exhibited a higher accumulation of phenols and flavonoids by triggering gene expression and activities of phenylalanine ammonia-lyase (PAL) and chalcone synthase (CHS). Moreover, the higher expression of L-galactotno-1,4-lactone dehydrogenase (GLDH) gene and the lower expression of ascorbic acid oxidase (AAO) gene in broccoli florets treated with 150 nM PSK alpha may be the reasons for the higher accumulation of ascorbic acid. In conclusion, the exogenous application of PSK alpha is a promising strategy in delaying the yellowing and preserving the nutritional quality of broccoli florets during cold storage.