Connecting Chlorophyll Metabolism with Accumulation of the Photosynthetic Apparatus

Optimal photosynthesis and proper leaf development rely on spatiotemporal regulation of Chl metabolism. Availability of Chl is crucial for the stability, correct folding, and membrane integration of CBPs; and Chl release occurs before the proteolysis of Chl-binding proteins. A conserved Chl assembly complex identified in arabidopsis (Arabidopsis thaliana) and cyanobacteria requires auxiliary factors, which may function either as Chl carriers or scaffold proteins that facilitate the integration of Chl into CBPs at the thylakoid membranes. A suite of post-translational regulators is implicated in the regulation of various aspects of Chl metabolism, and serve to coordinate the varying demand for Chl for biogenesis, maintenance, and degradation of the pigment–protein complexes. Chlorophyll (Chl) is indispensable for photosynthesis. In association with Chl-binding proteins (CBPs), it is responsible for light absorption, excitation energy transfer, and charge separation within the photosynthetic complexes. By contrast, photoexcitation of free Chl and its metabolic intermediates generates hazardous reactive oxygen species (ROS). While antagonistic activities of Chl synthesis and catabolism have been mostly elucidated, the tight synchronization of these metabolic activities with the formation and dismantling of the photosynthetic complexes is poorly understood. Recently, a set of auxiliary factors were identified to adjust metabolic activities and provide accurate amounts of Chl for pigment–protein complexes. Here, we review current knowledge of post-translational coordination of Chl formation, breakdown, and turnover with the assembly and disassembly of various CBPs and highlight future research perspectives. Chlorophyll (Chl) is indispensable for photosynthesis. In association with Chl-binding proteins (CBPs), it is responsible for light absorption, excitation energy transfer, and charge separation within the photosynthetic complexes. By contrast, photoexcitation of free Chl and its metabolic intermediates generates hazardous reactive oxygen species (ROS). While antagonistic activities of Chl synthesis and catabolism have been mostly elucidated, the tight synchronization of these metabolic activities with the formation and dismantling of the photosynthetic complexes is poorly understood. Recently, a set of auxiliary factors were identified to adjust metabolic activities and provide accurate amounts of Chl for pigment–protein complexes. Here, we review current knowledge of post-translational coordination of Chl formation, breakdown, and turnover with the assembly and disassembly of various CBPs and highlight future research perspectives. refer to two groups of transmembrane protein found in the chloroplasts of green plants, including the six plastid-encoded Chl a-binding proteins D1, D2, CP43, CP47, PsaA and PsaB, and the nuclear-encoded LHCPs, which are assembled in the PSII core complexes and peripheral light-harvesting complexes, respectively. hydrophobic Chl-binding proteins are incorporated into thylakoid membranes via the conserved cpSRP pathway, which comprises cpSRP43, cpSRP54, SRP receptor cpFtsY, and SRP translocase SecYE/Alb3. In addition to cpSRP43, the other components are highly conserved in both eukaryotes and prokaryotes. distant relatives of the classic LHCPs, which have one or two conserved CAB domains among up to four transmembrane domains. refers to the Chl catabolic pathway and acknowledges the tightly regulated enzymatic step catalyzed by PAO, which opens the chlorin ring of pheophytin a to produce the so-called phyllobilins. electronically excited form of oxygen that is produced in chloroplasts by the transfer of excitation energy from Chl and its metabolic intermediates to a ground state of oxygen. one of the most significant traits that is observed in various genetic variants with delayed leaf senescence; indicates the incomplete destruction of pigment–protein complexes. It is further classified into functional and nonfunctional categories depending on the photosynthetic competence. highly conserved branched metabolic pathway for the synthesis of cyclic or linear tetrapyrroles. The first committed precursor of tetrapyrrole biosynthesis is ALA and its synthesis is the rate-limiting step of the pathway. Photosynthetic organisms produce a diversity of tetrapyrroles, such as Chl, heme, siroheme, and several bilins, such as phycobilins and phytochromobilin.