Seasonal alteration of sugar metabolism in strawberry (Fragaria × ananassa) plants during cold-acclimated and non-acclimated stages

Abstract

Plants of strawberry cvs Aromas and Diamante were removed from the field in cold acclimated (CA, January) and non-acclimated (NA, July) stages. Crown parts of the plant were used for analysis. Apoplastic total soluble sugar (TSS), reducing sugars and sucrose contents did not change in both cultivars in both sampling stages. Symplastic TSS, reducing sugars and sucrose contents were higher in CA stage than that in NA stage in all  samples. Considering the cultivars, TSS, reducing sugars and sucrose contents were higher in Diamante than Aromas. The activity of acid  invertase (EC 3.2.1.26) enzyme was higher in NA stage than that in CA stage in the apoplast of crown tissues. In general, acid invertase activity in the symplast of crown tissues in both cultivars was higher in CA stage  compared with that in NA stage although not significantly, as a function of hardening. In addition generally, the cultivars had significantly higher  sucrose synthase (SS) (EC 2.4.2.13) activity in the symplast of crown  tissues when sampled at the CA than at the NA stage. In conclusion,  cold-hardiness of strawberry was suggested by increasing their TSS,  reducing sugars and sucrose contents significantly in the symplast of crown tissues in the CA stage. Moreover, both acid invertase and SS are  regulated by cold-acclimation and deacclimation.

Key words: Acid invertase, apoplast, cold-acclimation, Fragaria x ananassa, soluble sugar, strawberry, sucrose synthase, symplast.