Biology subjects

Danieli, R.

Publications and source records attributed to Danieli, R..

3 recordsLinked to original sources

bioRxiv2021

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

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 sugar units. Our results suggest that sugar units are better predictors of vegetative bud ED duration than chilling units.

plant biology↗

bioRxiv2020

Sucrose promotes etiolated stem branching through activation of cytokinin accumulation followed by vacuolar invertase activity

The potato (Solanum tuberosum L.) tuber is a swollen stem. Sprouts growing from the tuber nodes represent dormancy release and loss of apical dominance. We recently identified sucrose as a key player in triggering potato stem branching. To decipher the mechanisms by which sucrose induces stem branching, we investigated the nature of the inducing molecule and the involvement of vacuolar invertase (VInv) and the plant hormone cytokinin (CK) in this process. Sucrose was more efficient at enhancing lateral bud burst and elongation than either of its hexose moieties (glucose and fructose), or a slowly metabolizable analog of sucrose (palatinose). Sucrose feeding induced expression of the sucrose transporter gene SUT2, followed by enhanced expression and activity of VInv in the lateral bud prior to its burst. We observed a reduction in the number of branches on stems of VInv-RNA interference lines during sucrose feeding, suggesting that sucrose breakdown is needed for lateral bud burst. Sucrose feeding led to increased CK content in the lateral bud base prior to bud burst. Inhibition of CK synthesis or perception inhibited the sucrose-induced bud burst, suggesting that sucrose induces stem branching through CK. Together, our results indicate that sucrose is transported to the bud, where it promotes bud burst by inducing CK accumulation and VInv activity.

plant biology↗

bioRxiv2019

Vacuolar processing enzyme translocates to the vacuole through the autophagy pathway to induce programmed cell death

The caspase-like vacuolar processing enzyme (VPE) is a key factor in programmed cell death (PCD) associated with plant stress responses. Growth medium lacking a carbon source and dark conditions caused punctate labeling of 35S::VPE1-GFP (StVPE1-GFP) in potato leaves. Carbon starvation of BY-2 cells induced higher VPE activity and PCD symptoms. Growing VPE-RNAi BY-2 cells without sucrose reduced VPE activity and prevented PCD symptoms. During extended exposure to carbon starvation, VPE expression and activity levels peaked, with a gradual increase in BY-2 cell death. Histological analysis of StVPE1-GFP in BY-2 cells showed that carbon starvation induces its translocation from the endoplasmic reticulum to the central vacuole, through tonoplast engulfment. Exposure of BY-2 culture to the autophagy inhibitor concanamycin A caused autophagic bodies accumulation in the cell vacuole. Such accumulation did not occur in the presence of 3-methyladenine, an inhibitor of early-stage autophagy. BY-2 cells constitutively expressing StATG8IL-RFP, an autophagosome marker, showed colocalization with the StVPE1-GFP protein in the cytoplasm and vacuole. RNAi silencing of the core autophagy component ATG4 in BY-2 cells reduced VPE activity and cell death. These results are the first to suggest that VPE translocates to the cell vacuole through the autophagy pathway, leading to PCD.\n\nOne sentence summaryCarbon starvation induced programmed cell death by trafficking vacuolar processing enzyme through the autophagy pathway to the vacuole.

plant biology↗