Chlorophyll Biosynthesis

description32 papers

group6 followers

lightbulbAbout this topic

Chlorophyll biosynthesis is the biochemical process by which chlorophyll pigments are produced in plants, algae, and cyanobacteria. This process involves a series of enzymatic reactions that convert precursors into chlorophyll molecules, essential for photosynthesis and light absorption.

lightbulbAbout this topic

Key research themes

1. How do mutations and isoform variants of Mg chelatase subunits affect chlorophyll biosynthesis and chloroplast function in green algae and plants?

This research area focuses on elucidating the roles of different isoforms and subunits of the Mg chelatase enzyme complex, particularly CHLI variants, in catalyzing the insertion of Mg2+ into protoporphyrin IX, a key step in chlorophyll biosynthesis. Understanding the molecular consequences of genetic mutations and expression levels of these subunits clarifies their contribution to chlorophyll production, retrograde signaling, and photosynthetic apparatus assembly in model organisms such as Chlamydomonas reinhardtii and Arabidopsis. This has broader implications for unraveling regulatory feedback and potential genetic engineering targets to improve photosynthetic efficiency.

Identification and molecular characterization of a novel mutant defective in chlorophyll Chlamydomonas reinhardtii biosynthesis

by Mautusi Mitra

2022

Key finding: This study isolated the first Chlamydomonas reinhardtii chli1 mutant deficient in chlorophyll biosynthesis, demonstrating that loss of CHLI1 abolishes Mg chelatase activity, resulting in complete chlorophyll absence and light... Read more

articleView Paper downloadDownload

What future union? The struggle for a social Europe

by Bieler Andreas

2022, Queen's Papers on Europeanisation

Key finding: The knockout of CHLI1 in Chlamydomonas caused a complete loss of Mg chelatase activity and chlorophyll, along with downregulation of key photosynthesis-associated nuclear genes, demonstrating CHLI1's central role in... Read more

articleView Paper downloadDownload

Light Intensity-Dependent Modulation of Chlorophyll b Biosynthesis and Photosynthesis by Overexpression of Chlorophyllide a Oxygenase in Tobacco

by FNU Govindjee

2015

Key finding: Overexpression of full-length Arabidopsis CAO in tobacco increased chlorophyll b biosynthesis and decreased the chlorophyll a/b ratio, especially under high light. This upregulated light-harvesting complex proteins and... Read more

articleView Paper downloadDownload

Phytochrome B Mediates the Regulation of Chlorophyll Biosynthesis through Transcriptional Regulation of ChlH and GUN4 in Rice Seedlings

by Makoto Takano

2022, PLOS ONE

Key finding: Phytochrome B (phyB) mutants in rice showed a pale-green phenotype due to reduced expression of Mg-chelatase subunit genes ChlH and GUN4 during red-light induced greening. This transcriptional repression correlated with... Read more

articleView Paper downloadDownload

keyboard_arrow_downShow more

2. What molecular and structural mechanisms underlie chlorophyll f biosynthesis and the extension of photosynthesis into the far-red spectrum?

This theme investigates the genetic, enzymatic, and evolutionary basis of chlorophyll f synthesis, a modified chlorophyll that absorbs far-red light, enabling photosynthetic organisms to extend their light usage beyond the visible spectrum. Understanding the enzyme(s) responsible for chlorophyll f production and how they integrate into photosystem complexes provides critical insights into photosynthesis adaptation, with potential applications in crop improvement. Studies employ reverse genetics and heterologous expression primarily in cyanobacteria to reveal biosynthetic pathways enabling survival under far-red light conditions.

Light-dependent chlorophyll f synthase is a highly divergent paralog of PsbA of photosystem II

by Gaozhong Shen

2021, Science

Key finding: Reverse genetics identified a highly divergent paralog of the psbA gene, designated chlF, encoding a light-dependent chlorophyll f synthase that catalyzes the biosynthesis of chlorophyll f in cyanobacteria under far-red... Read more

articleView Paper downloadDownload

keyboard_arrow_downShow more

3. How is the entire chloroplast genome transcriptionally regulated and what implications does this have for chlorophyll biosynthesis and chloroplast function?

This research theme explores chloroplast genome-wide transcription patterns revealing that virtually the entire plastome is transcribed in photosynthetic eukaryotes, contrary to earlier models suggesting discrete transcription units. By analyzing transcriptomic data across diverse taxa, this area uncovers a multiple arrangement transcription model involving overlapping and heterogeneous transcript isoforms. Such pervasive transcription has significant implications for chlorophyll biosynthesis regulation, chloroplast development, and retrograde signaling involving chloroplast-nuclear coordination.

Full transcription of the chloroplast genome in photosynthetic eukaryotes

by En-Hua Xia

2021, Scientific reports

Key finding: Analysis of plastid transcriptomes across algae, higher plants, and cyanobacteria revealed more than 99% coverage of entire plastomes, demonstrating full plastome transcription beyond discrete operons. The findings support a... Read more

articleView Paper downloadDownload

keyboard_arrow_downShow more

All papers in Chlorophyll Biosynthesis

Prolamellar body: A unique plastid compartment, which does not only occur in dark- grown leaves

by Katalin Solymosi and

Chloroplast development is usually considered to proceed from proplastids to chloroplasts. Different, either direct or indirect conversion pathways have been described in the literature, the latter involving either the etio-chloroplast or... more

Prolamellar bodies in chloroplasts and etioplasts Figure 1. Different plastid types and their interconversions. (a) Typical lens-shapec chloroplast from lettuce (Lactuca sativa) leaf, (b) chromoplast from carrot (Daucu: carota) root containing electron dense plastoglobuli and a few inner membranes, (c gerontoplasts from the seed coat of Gleditsia triacanthos, (d) scheme of the interconversions of the most important plastid types. Interconversion pathways drawr and modified after Keresztes [43] with permission. The bar represents 1 um. C carotene crystal-like structure, Cw: cell wall, E: envelope, G: granum, P: plastid, Pg plastoglobuli, S: stroma, ST: stromal thylakoid, V: vacuole.

Figure 2. (a) Etioplast from the innermost leaf of kale (B. oleracea cv. sabauda) head. (b) Etio-chloroplast with large grana and interconnected PLBs from the low (20 umol sm”) light-exposed region of 7-day old sunflower (Helianthus annuus) cotyledon. The bar represents | wm. Cw: cell wall, E: envelope, G: grana, M: mitochondrium, PLB: prolamellar body, PT: prothylakoid, S: starch, V: vacuole. Prolamellar bodies in chloroplasts and etioplasts

Figure 3. (a) Etioplast from 7-day old wheat (Triticum aestivum) leaves. Prolamellar bodies isolated according to the method of Ouazzani-Chahdi et al. [33 slightly modified by Mysliwa-Kurdziel et al. [332] from the leaves of 7-day old dark- grown wheat (courtesy by Dr. K. Boka). The bar represents 1 um. Cw: cell wall, | envelope, M: mitochondrium, Pg: plastoglobuli, prothylakoid, V: vacuole. (b 1] TD EK: PLB: prolamellar body, PT: creates an 1cOSsanedral snape. According to Gunning and Steer [25], the two most common PLB geometries are analogues of the arrangement of the atoms in the crystal lattice of zinc sulphide, i.e. they correspond to wurtzite or zincblende crystal forms. The zincblende type of arrangement is also found in diamond. The most common structure in oat is the wurtzite type, when tetrahedrally branched tubular units are hexagonally arranged [20,25]. In the zincblende (or diamond type) lattice six tetrapodel (tetrahedral) units form a hexagon, and the hexagons are held together in a structure of the same symmetry as the carbon atoms in the diamond crystal [20,25,221]. This arrangement (diamond cubic or Fd3m symmetry) was proved by the use of X-ray diffraction [231,330]. Based on the spacing of the membrane tubules, Henningsen and Boynton [108] defined narrow-type and wide-type PLBs, the former having a relatively narrow spacing of the membrane tubules, while the latter present less compact packing [108-109,289]. PLBs with unusual, relatively wide-spacing were also termed “open” PLBs [25,91,230] or noncrystalline PLBs [21]. Gunning [91] has shown that the “open” PLBs of barley and oat consist of confluent tetrahedrally branched tubules delimiting pentagonal dodecahedra and larger 14- and 15-hedra, which, in turn, are combined by face-sharing in a lattice that has counterparts in certain clathrate-hydrate inclusion compounds. The physiological significance of the different types of PLBs is not known. Both wide- and narrow-type PLBs can occur ina single species within the same

Katalin Solymosi & Benoit Schoefs Figure o. Flastid developmental pathways reviewed In this Cnapter. A: In case of seedlings germinating in the soil and in some special structures (i.e., cabbage heads, avocado and pepo fruits) chlorenchymatic tissues develop in complete darkness also under natural conditions. In the latter cases the plastid differentiation is arrested at the etioplast stage under natural conditions (for details see Section 2.2.).

Table 3. Unit cell size of PLBs determined in different plant species. From the periphery of the PLBs, flat, 1-2 um long lamellar membran« resembling stromal thylakoids are radiating into the stroma. They are terme PTs [153,282]. Perforations on the PTs as well as sometimes the parall arrangement of continuous PT-stacks might be observed (barley: [108,240 pean: [262], maize: [104,210], oat: [102], wheat: e.g., Fig. 3a). The paire (stacked) regions are usually rather long and the space between the layer! appears to be wider than the space between the discs of grana [247]. The rati of PT and PLB membranes within the etioplasts can differ among specie organs and tissues and also during the ageing of the plant and depends also o the growth conditions [335]. In few studies it has been shown that the PT usually react differently to osmotic shock or to different osmotic conditior than the PLBs. For example under salt stress the PLBs retain their crystallin

descriptionView Paper arrow_downwardDownload

Etioplast and etio-chloroplast formation under natural conditions: the dark side of chlorophyll biosynthesis in angiosperms

by Katalin Solymosi and

Chloroplast development is usually regarded as proceeding from proplastids. However, direct or indirect conversion pathways have been described in the literature, the latter involving the etioplast or the etio-chloroplast stages.... more

Fig. 1 Scheme summarizing the most important conditions in which prolamellar bodies (PLBs) have been reported to occur under natural conditions. * PLBs were reported only in young plants or young plant organs, ** most often young plants have been studied, but rarely PLBs were also found in mature plant tissues

Fig. 2. Prolamellar body (PLB) containing plastids from plants grown under natural conditions. a Etioplast from the innermost leaf of kale (Brassica oleracea cv. sabauda) head. b Etio-chloroplast from the innermost leaf primordia of opening horse chestnut (Aesculus hippocastanum) buds collected under natural conditions during daytime. ¢ Etio-chloroplast with large grana and interconnected PLBs from the light-exposed region of 7-day-old sunflower (Helian- thus annuus) cotyledon grown under continuous low-light conditions (20 umol s-'m~*). Bar: 1 um. G grana, Lg low grana, PLB prolamellar body, S starch

of buds are presented. On these pictures the pale yellow color of the leaf primordia as well as the several overlapping layers can be clearly observed. Bar: 1 cm Fig. 3 Horse chestnut (Aesculus hippocastanum) bud development from completely closed buds characteristic for winter (/eft side) to opening/breaking buds characteristic for spring (end of March, beginning of April in Hungary). On the insets, longitudinal sections

Fig. 5 Dynamic model showing the main regulation network providing the conditions for PLB formation at the beginning of greening and during the dark phases of LDC. The data reviewed above converge to the fact that PLB formation during the dark phase of LDC occurs only during the period during which Mg-tetrapyrrole synthesis is intense. Therefore, the model is organized around the Chl biosynthetic pathway. Black arrows indicate logical relationships, whereas green and red arrows suggest positive and negative interactions, respectively. The dynamics is indicated using two positions of traffic lights indicating the activity of the pathway in the dark (up) or light (down) phase of the LDC. The colors red, orange, and green at one of the positions of the traffic light mean no activity, some activity and fully active, respectively; white color indicates that there are no data about the enzyme activity. BD means that the value of the relation as indicated in the scheme is only valid at the beginning of the development. The active and inactive states of an enzyme are indicated by an oval and a triangle, respectively. Thick and empty arrows specify genes. Phosphorylation of a protein is indicated by a P in a circle, At stands for Arabidopsis thaliana. For abbreviations see the text

Fig. 6 Chloroplast developmental pathways summarized in this article. Under natural light-dark cycles or at low light intensities, proplastids differentiate to etio-chloroplasts (route 1), before being converted into chloroplasts (route 4), and this route is reversible until the end of chloroplast maturation, because prolamellar bodies are reformed in the young chloroplasts during the dark phase of the light— dark cycles (route 5). The plastids of seedlings germinating in the soil or in plant structures providing a strong shading effect to inner tissues, proplastid differentiation may be arrested at the etioplast stage under natural conditions (route 2) but if the dark condition is disrupted, etioplasts get transformed into chloroplasts through the etio-chloro- plast stage (routes 3 and 4). Under high light intensity, proplastids differentiate into chloroplasts without prolamellar body formation (route 6) proplastids differentiate into etioplasts and develop PLBs even in tissues growing under LDCs. Consequently, eti- oplasts and PLBs should not be regarded only as laboratory artefacts but as natural plastid developmental stages, pro- vided that the adequate growth context is considered. Careful examination of the literature data and our own results indicate that the chloroplast developmental stage is reached according to three main developmental routes among which two include PLB formation (Fig. 6). The exact mechanism of PLB formation, its role(s) in the greening process, and in chloroplast functioning especially in natural conditions still need to be elucidated. Many factors, especially light intensity, regulate PLB formation (Fig. 1). The understanding of the regulation of PLB for- mation will provide important information about the role of PLBs in the greening process and in the adaptation of the developing chloroplasts to changes of the light environ- ment. Many authors have suggested that PLBs may have a role in lipid storage (Gunning 2001; Selstam and Widell- Wigge 1993; Virgin and Egnéus 1983), which enables the fast formation of chloroplast thylakoids, once the plant gets exposed to high-light conditions. The fact that PLBs often appear in “non-mature” plastids of young tissues or young seedlings, or in plants which have not reached their final Chl content, or the final size of their mature chloroplasts also underlines that PLBs play an important role in Chl biosynthesis and thylakoid formation.

descriptionView Paper arrow_downwardDownload

Light Intensity-Dependent Modulation of Chlorophyll b Biosynthesis and Photosynthesis by Overexpression of Chlorophyllide a Oxygenase in Tobacco

by FNU Govindjee

Chlorophyll b is synthesized by the oxidation of a methyl group on the B ring of a tetrapyrrole molecule to a formyl group by chlorophyllide a oxygenase (CAO). The full-length CAO from Arabidopsis (Arabidopsis thaliana) was overexpressed... more

descriptionView Paper arrow_downwardDownload

Light Intensity-Dependent Modulation of Chlorophyll b Biosynthesis and Photosynthesis by Overexpression of Chlorophyllide a Oxygenase (CAO) in Tobacco

by Shiv Pandey

2012, Plant physiology

Chlorophyll b is synthesized by the oxidation of a methyl group on the B ring of a ttrapyrrole molecule to a formyl group by chlorophyllide a oxygenase (CAO). The full length CAO, from Arabidopsis thaliana was overexpressed in tobacco... more

descriptionView Paper arrow_downwardDownload

Chlorophyll Biosynthesis

Key research themes

1. How do mutations and isoform variants of Mg chelatase subunits affect chlorophyll biosynthesis and chloroplast function in green algae and plants?

2. What molecular and structural mechanisms underlie chlorophyll f biosynthesis and the extension of photosynthesis into the far-red spectrum?

3. How is the entire chloroplast genome transcriptionally regulated and what implications does this have for chlorophyll biosynthesis and chloroplast function?

Related Topics

All papers in Chlorophyll Biosynthesis