Sugar units, not chilling units, control endodormancy duration in plants – potato tuber as a case study

Abstract

Endodormancy (ED) is a crucial stage in the life cycle of many perennial plants, regulated by genetic and environmental factors. Chilling units, growth regulators, and nutrient supply are considered inducers of ED release, but the mechanism governing ED duration is poorly understood. The potato tuber has been used as a model system to study metabolic processes associated with ED release. Cold-induced sweetening is a well-known response of the tuber to chilling. Here, we found that cold stress induces an increase in sugar units in association with plasmodesmatal closure in the dormant bud cells. Tuber sweetening was associated with shortened ED duration after cooling. Heat exposure also caused sugar unit accumulation followed by faster ED release. A logistic function was developed to predict ED duration based on sugar unit measurements. We discovered that ED release is better correlated with the accumulation of sugar units compared to chilling units. CRISPR/Cas9 knockout of the vacuolar invertase gene (StVInv) induced longer ED, but only in cultivars in which the mutation modified the level of sugar units. Our results suggest that sugar units are better predictors of vegetative bud ED duration than chilling units.

GhbZIP30‐GhCCCH17 module accelerates corm dormancy release by reducing endogenous ABA under cold storage in Gladiolus

“…During dormancy release in potato tubers, phloem connectivity changes promote sucrose transport into the buds to supply assimilates for bud growth. It has even been suggested that sugar units are better predictors of vegetative bud endodormancy duration than chilling units (Danieli et al, 2021; Sonnewald & Sonnewald, 2014). Recently, several studies revealed that sugars promote bud outgrowth and inhibit para‐dormancy in perennials (Bertheloot et al, 2020).…”

“…They promote plant growth with T6P acting as a sugar sensor, as well as by supplying resources for cellular activities (Pan et al, 2021). It is well‐known that the crosstalk between sugars and ABA can be mediated by the T6P‐SnRK1 and SnRK1‐TOR‐SnRK2 modules (Danieli et al, 2021; Debast et al, 2011; Pan et al, 2021). In Gladiolus, sugar accumulation is repressed by ABA during corm dormancy induction (Li et al, 2021).…”

“…Furthermore, glucose provides energy for accelerated cell division via glycolysis and the TCA (tricarboxylic acid) cycle (Zhao et al, 2022). In potato, knocking out a vacuolar acid invertase ( StVInv ) delays endodormancy release because of decreased sugar units (Danieli et al, 2021). In addition, sugars can serve as a signal regulating cell division and the biosynthesis of DNA and proteins via the SnRK1 (SNF1‐related protein kinase 1)‐TOR1 (Target of Rapamycin) module (Danieli et al, 2021; Debast et al, 2011).…”

“…In potato, knocking out a vacuolar acid invertase ( StVInv ) delays endodormancy release because of decreased sugar units (Danieli et al, 2021). In addition, sugars can serve as a signal regulating cell division and the biosynthesis of DNA and proteins via the SnRK1 (SNF1‐related protein kinase 1)‐TOR1 (Target of Rapamycin) module (Danieli et al, 2021; Debast et al, 2011). In potatoes, T6P ( TREHALOSE‐6‐PHOSPHATE ) regulates tuber dormancy release by mediating SnRK1 levels (Debast et al, 2011).…”

“…Furthermore, glucose provides energy for accelerated cell division via glycolysis and the TCA (tricarboxylic acid) cycle (Zhao et al, 2022). In potato, knocking out a vacuolar acid invertase (StVInv) delays endodormancy release because of decreased sugar units (Danieli et al, 2021).…”