A sucrose transporter‐interacting protein disulphide isomerase affects redox homeostasis and links sucrose partitioning with abiotic stress tolerance

Abstract

Sucrose accumulation in leaves in response to various abiotic stresses suggests a specific role of this disaccharide for stress tolerance and adaptation. The high-affinity transporter StSUT1 undergoes substrate-induced endocytosis presenting the question as to whether altered sucrose accumulation in leaves in response to stresses is also related to enhanced endocytosis or altered activity of the sucrose transporter. StSUT1 is known to interact with several stress-inducible proteins; here we investigated whether one of the interacting candidates, StPDI1, affects its subcellular localization in response to stress: StPDI1 expression is induced by ER-stress and salt. Both proteins, StSUT1 and StPDI1, were found in the detergent resistant membrane (DRM) fraction, and this might affect internalization. Knockdown of StPDI1 expression severely affects abiotic stress tolerance of transgenic potato plants. Analysis of these plants does not reveal modified subcellular localization or endocytosis of StSUT1, but rather a disturbed redox homeostasis, reduced detoxification of reactive oxygen species and effects on primary metabolism. Parallel observations with other StSUT1-interacting proteins are discussed. The redox status in leaves seems to be linked to the sugar status in response to various stress stimuli and to play a role in stress tolerance.

The redox state of the apoplast influences the acclimation of photosynthesis and leaf metabolism to changing irradiance

“…StPDI1 ‐silenced plants have low ascorbate levels and show increased H 2 O 2 accumulation under stress conditions (Eggert et al . ). However, it is worth noting that the action of AO may extend far beyond simple effects due to changes in AO activity.…”

“…Sucrose transport is also sensitive to the redox environment of the apoplastic/cell wall compartment. The SUT family of sucrose transporters interact with StPDI1, a protein disulphide isomerase (Eggert et al ). StPDI1 ‐silenced plants have low ascorbate levels and show increased H 2 O 2 accumulation under stress conditions (Eggert et al .…”

Carbon export from leaves is controlled via ubiquitination and phosphorylation of sucrose transporter SUC2

“…Furthermore, the increased biomass and yield of plants lacking a regulator observed here demonstrate that manipulation of SUC regulation can be a viable path to enhance plant productivity. sucrose transport activity (12)(13)(14)(15). Kinase activity influences the abundance of BvSUT1, either through phosphorylation of the transporter itself or of regulatory proteins (16).…”

Subcellular Targeting of Plant Sucrose Transporters Is Affected by Their Oligomeric State

“…StSUT1 was shown to be associated to lipid raft-like microdomains in a redox-dependent manner and recycled in highly motile vesicles at the sieve element plasma membrane [9]. In the presence of high sucrose concentration (>500 mM sucrose), StSUT1 endocytosis is stimulated [10], whereas at lower sucrose concentration most of the protein is detected at the plasma membrane. Similar observation was made in the presence of brefeldin A, cycloheximide, or both, enhancing vesicle formation and StSUT1 internalization [11].…”

“…All sucrose transporter and interaction partner cDNAs were cloned by GATEWAY technology after a two-step PCR protocol into the ENTRY vector pDONR221 and subsequently cloned via LR reaction in the appropriate destination vector as described previously [2, 10,12,33]. For Bimolecular Fluorescence Complementation (BiFC) assay, full length sucrose transporter cDNAs were fused to Nand C-terminal sub-fragments of the yellow fluorescent protein (YFP) in the GATEWAY cloning vectors: pDEST-VYNE and pDEST-VYCE [13] to study homodimerization.…”