The roles of starch metabolic pathways in the cold‐induced sweetening process in potatoes

Abstract

Cold-induced sweetening (CIS) is critical for the postharvest quality of potato tubers, and the accumulation of reducing sugar is regulated by several metabolic pathways, such as starch synthesis and degradation, hexogenesis, glycolysis, and anaerobic respiration. Starch is the energy source of storage organs, and its metabolism plays an important role in potato CIS. Here, the processes of starch synthesis and degradation in potato tubers and the functions of related genes in potato CIS are summarized, e.g., adenosine diphosphate glucose pyrophosphorylase, starch synthases, branching enzymes, and debranching enzymes for starch biosynthesis as well as a-amylase, b-amylase, amylase inhibitors, and starch phosphorylase for starch degradation. Powerful evidence concerning the relevance of genes related to starch degradation and CIS is described. Moreover, future perspectives in starch metabolic research are discussed.

Differential DNA methylation in theVinvpromoter region controls Cold Induced Sweetening in potato

“…Furthermore, studies have revealed that in addition to the VINV pathway, sucrose is also broken down to UDP-glucose and fructose via the sucrose synthase (SuSy) pathway 13,21 (Fig. S1A).…”

“…Sucrose levels increased with storage time for Verdi but decreased for the CIS-susceptible varieties. Conversion of sucrose to reducing sugars is known to occur simultaneously through two pathways: the VINV pathway and the sucrose synthase (SuSy) pathway 13,21 . The very low activity of the VINV pathway in Verdi forces sucrose to be broken down through the SuSy pathway to produce UDP-Glucose which is subsequently converted back to sucrose through a series of enzymatic reactions (Fig.…”

“…Several studies have demonstrated the implication of these processes in CIS 16–20 . However, the amount of reducing sugars generated in the potato tubers is the function of a synergistic action of the enzymes catalyzing the afore-mentioned processes and the interrelated pathways of starch synthesis, glycolysis, and respiration 13,21 . The bottleneck for CIS is the conversion of sucrose to glucose and fructose, catalyzed mainly by invertases and sucrose synthase 13,21 .…”

“…However, the amount of reducing sugars generated in the potato tubers is the function of a synergistic action of the enzymes catalyzing the afore-mentioned processes and the interrelated pathways of starch synthesis, glycolysis, and respiration 13,21 . The bottleneck for CIS is the conversion of sucrose to glucose and fructose, catalyzed mainly by invertases and sucrose synthase 13,21 . A strong correlation between vacuolar invertase (VINV) activity and reducing sugars content makes Vinv the primary determinant of CIS in potato tubers 16,22,23 .…”

The Solanum Tuberosum Knowledge Base: The Section on Molecular-Genetic Regulation of Metabolic Pathways

“…Крахмалсинтаза, связанная с крахмальными гранула-ми (granule-bound starch synthase), ответственна за синтез амилозы, тогда как растворимые крахмалсинтазы I-III от-вечают за синтез амилопектина. Ветвление амилопектина осуществляет ветвящий фермент SBE (starch-branching enzyme, EC 2.4.1.18), который отщепляет от неразветвлен-ной цепочки фрагмент и переносит его к шестому атому углерода глюкозы (Zhang et al, 2017). Путь биосинтеза крахмала описан во многих источниках, в то время как регуляция этого процесса до сих пор остается малоизу-ченной (Van Harsselaar et al, 2017).…”