The multistress‐induced Translocator protein (TSPO) differentially modulates storage lipids metabolism in seeds and seedlings

Abstract

Translocator proteins (TSPO) are conserved membrane proteins extensively studied in mammals, but their function is still unclear. Angiosperm TSPO are transiently induced by abiotic stresses in vegetative tissues. We showed previously that constitutive expression of the Arabidopsis TSPO (AtTSPO) could be detrimental to the cell. Degradation of AtTSPO requires an active autophagy pathway. We show here that genetic modifications of TSPO expression in plant and yeast cells reduce the levels of cytoplasmic lipid droplets (LD). Transgenic Arabidopsis seedlings overexpressing AtTSPO contain less LD as compared with wild type (WT). LD levels were increased in Arabidopsis AtTSPO knockout (KO) seedlings. Deletion of the Schizosaccharomyces pombe TSPO resulted in an increase in LD level in the cell. As compared with the WT, the mutant strain was more sensitive to cerulenin, an inhibitor of fatty acids and sterol biosynthesis. We found that in contrast with seedlings, overexpression of AtTSPO (OE) resulted in an up to 50% increase in seeds fatty acids as compared with WT. A time course experiment revealed that after 4 days of seed imbibition, the levels of triacylglycerol (TAG) was still higher in the OE seeds as compared with WT or KO seeds. However, the de novo synthesis of phospholipids and TAG after 24 h of imbibition was substantially reduced in OE seeds as compared with WT or KO seeds. Our findings support a plant TSPO role in energy homeostasis in a tissue-specific manner, enhancing fatty acids and LD accumulation in mature seeds and limiting LD levels in seedlings.

Root Skewing-Associated Genes Impact the Spaceflight Response of Arabidopsis thaliana

“…Given that sku5 shows alterations of ABA signaling pathways in spaceflight (Figure 13), it can be hypothesized that the lack of SKU5 may affect the function of these nanodomain-localized ABA signaling processes under stress conditions. The expression of a chloroplastic aldehyde reductase, ChlADR (AT1G54870), involved in the detoxification of reactive carbonyls formed as a result of lipid peroxidation, and TSPO, which participates in mobilization of lipids, are induced by stress and highly induced in the spaceflight acclimation of sku5 (Guillaumot et al, 2009;Yamauchi et al, 2011;Jurkiewicz et al, 2018). These patterns match the gene expression trends of the spaceflight-induced LEA family genes that are thought to directly participate in membrane stabilization under stress (Battaglia et al, 2008;Hundertmark and Hincha, 2008;Candat et al, 2014).…”

Investigation of a Novel Salt Stress-Responsive Pathway Mediated by Arabidopsis DEAD-Box RNA Helicase Gene AtRH17 Using RNA-Seq Analysis

“…The C-terminal region of LEA4-5 is responsible for its antioxidant activity and in the scavenging of metal ions under stress conditions, whereas the N-terminal can function as a chaperone in the folding of enzyme proteins and in preventing their unfolding that results in protection of the enzyme activity [19,30]. TSPO, belonging to the Trp-rich sensory protein/peripheral-type benzodiazepine receptor group protein, interacts with and regulates PIP2;7, a plasma membrane aquaporin, in the endoplasmic reticulum and Golgi membrane during abiotic stress conditions [20,21]. The interaction between TSPO and PIP2;7 triggers the reduction of PIP2;7 channels present in the plasma membrane and reduces the water transport activity [20,21].…”

“…TSPO, belonging to the Trp-rich sensory protein/peripheral-type benzodiazepine receptor group protein, interacts with and regulates PIP2;7, a plasma membrane aquaporin, in the endoplasmic reticulum and Golgi membrane during abiotic stress conditions [20,21]. The interaction between TSPO and PIP2;7 triggers the reduction of PIP2;7 channels present in the plasma membrane and reduces the water transport activity [20,21]. ABR is a Ser/Thr kinase and interacts with phospholipase D-derived phosphatidic acid (PA) [31,32].…”

“…The biological functions of LEA proteins in osmotic stress-tolerance are well known [18,19]. TSPOs have also been shown to be responsive to salt and osmotic stresses and ABA [20,21]. Quantitative RT-PCR analysis showed that the expression levels of LEA4-5, ABR, and TSPO were higher in AtRH17 OXs than in WT under salt stress conditions (Figure 7).…”

TSPO protein binding partners in bacteria, animals, and plants

“…In plants, however, TSPO has been primarily reported to be a monomer. A monomer form of 18–22 kDa was found in Arabidopsis thaliana in a variety of tissues (Lindemann et al 2004 ; Guillaumot et al 2009a ; Hachez et al 2014 ; Jurkiewicz et al 2018 , 2020 ), although an early paper showed the presence of a possible dimer in potato (Corsi et al 2004 ) and monomer and potential dimer forms were detected in Digitalis lanata cell cultures (Lindemann et al 2004 ). More experimentation will be necessary to establish the potential for formation and functional significance of oligomeric forms in plants and other species.…”