Starch-related enzymes during potato tuber dormancy and sprouting

Abstract

Activities of enzymes presumably involved in starch biosynthesis (ADP glucose pyrophosphory lase, AGPase) and/or breakdown (starch phosphorylase, STP; amylases) were determined during potato (Solanum tuberosum L.) tuber dormancy and sprouting. Overall activities of all these enzymes decreased dur ing the first stage of tuber dormancy. No clear changes were detected at the time of dormancy breaking and sprouting. However, when AGPase activity was monitored by in situ staining during the entire dormancy period, a clear decrease during the dormant period and a large increase before visible sprouting could be observed. This increase was especially evident near the vascular tissue and at the apical bud, which showed a very intensive staining. In situ staining of STP activity in sprouting tubers showed that the tissue distribution of STP was the same as for AGPase. As a possible explanation, direct starch cycling is suggested: STP pro duces glucose 1 phosphate during starch breakdown, which can be directly used as a substrate by AGPase for starch synthesis. Gene expression studies with the AGPaseS promoter coupled to the firefly luciferase reporter gene also clearly showed a higher activity in sprouting tubers as compared to dormant tubers, with the highest expression levels observed around the apical buds. The presence of amylase activity at dormancy initiation and AGPase activity persistent at the sprouting stage suggest that starch was cycling throughout the entire dormancy period. According to the in situ studies, the AGPase activity increased well before visible sprout growth and could therefore be one of the first physiological determinants of dormancy breakage.

Transcriptome analyses provide insights into the homeostatic regulation of axillary buds in upland cotton (G. hirsutum L.)

“…These findings supported the traditional opinion that the bud is a site of the nutrient accumulation and storage and that plants with more buds show more nutrient accumulation [60]. A previous study also indicated that tubers are storage organs that accumulate starch during the development of potato [61]. Starch degradation results in an increase in the soluble sugar concentration; thus, starch may play an important role in the accumulation of endogenous soluble sugars in cells [62].…”

Seed Germination and Seedling Growth of Dendrocalumus brandisii in vitro, and the Inhibitory Mechanism of Colchicine

“…For the activity determination of starch-metabolizing enzymes, the crude enzyme was extracted according to Nakamura et al ( 1989 ) and Sergeeva et al ( 2012 ). All the procedures were carried out at 0°C.…”

Immersion in 6-Benzylaminopurine for Dormancy Release and Initiation of Potato Sprouts at Various Tuber Weight and Storage Duration

“…This is related to the adequacy of energy reserves in the form of carbohydrates in the tubers which are used by the enzymes during the germination process. During the tuber development process, the presence of amylase activity is important in the starch cycle, where Β-amylase activity decreases at the beginning of dormancy and then increases after initiation of sprouts (Sergeeva et al, 2012).…”