Abstract
Cell compartmentalization allows incompatible chemical reactions and localised responses to occur simultaneously, however, it also requires a complex system of communication between compartments in order to maintain the functionality of vital processes. It is clear that multiple such signals must exist, yet little is known about the identity of the key players orchestrating these interactions or about the role in the coordination of other processes. Mitochondria and chloroplasts have a considerable number of metabolites in common and are interdependent at multiple levels. Therefore, metabolites represent strong candidates as communicators between these organelles. In this context, vitamins and similar small molecules emerge as possible linkers to mediate metabolic crosstalk between compartments. This review focuses on two vitamins as potential metabolic signals within the plant cell, vitamin C (L-ascorbate) and vitamin B1 (thiamin). These two vitamins demonstrate the importance of metabolites in shaping cellular processes working as metabolic signals during acclimation processes. Inferences based on the combined studies of environment, genotype, and metabolite, in order to unravel signaling functions, are also highlighted.
Highlights
The different cellular compartments such as chloroplasts, mitochondria, and the nucleus require a tightly orchestrated coordination of metabolic activity within each compartment by anterograde and retrograde signaling pathways [1,2]
Given that ascorbate production is tightly associated with the mitochondrial electron transport chain and considering the well-documented facts on having profound bidirectional relationships with the rates of photosynthesis via a range of mechanisms, we assume that ascorbate takes part in the coordination of the energy systems between the mitochondria and chloroplast
TK has a central location in the Calvin–Benson cycle catalyzing the reversible transfer of a molecule with two carbons from sedoheptulose 7-phosphate to glyceraldehyde 3-phosphate (G3P), generating xylulose 5-phosphate (Xu5P) and ribose 5-phosphate, or from fructose 6-phosphate to produce Xu5P and erythrose 4-phosphate
Summary
The different cellular compartments such as chloroplasts, mitochondria, and the nucleus require a tightly orchestrated coordination of metabolic activity within each compartment by anterograde and retrograde signaling pathways [1,2]. Several classes of factors including organelle gene expression, redox status, accumulation of pigment precursors like tetrapyrroles, reactive oxygen species (ROS), and metabolites have been proposed to act as plastidial signals [1] They are sensed by plastidial factors including Executer, Executer, Genomes Uncoupled 1 (GUN1), and a thylakoid protein kinase (STN7), to initiate signaling cascades [1,4]. Thiamin has been shown to be involved in the acclimation responses to abiotic stresses and photoperiod [28,29,30,31,32] It plays important roles, working directly as an antioxidant, scavenging ROS, and protection molecule, and indirectly by contributing to the cell energy poll, conferring the cell the necessary metabolic flexibility to acclimate to new conditions [17,32,33]. A detailed description of each pathway and their roles in plant acclimation responses to environmental cues, in particular high light and photoperiod acclimation, are discussed
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