Proteomic Analysis of the Eyespot of<i>Chlamydomonas reinhardtii</i>Provides Novel Insights into Its Components and Tactic Movements

Schmidt, M; Geßner, Gunther; Luff, Matthias; Heiland, Ines; Wagner, Volker; Kaminski, Marc; Geimer, Stefan; Eitzinger, Nicole; Reißenweber, Tobias; Voytsekh, Olga; Fiedler, Monika; Mittag, Maria; Kreimer, Georg

doi:10.1105/tpc.106.041749

Cited by 176 publications

(220 citation statements)

References 105 publications

(154 reference statements)

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“…The COP2 protein may be unlikely to function in PSI biogenesis, because silencing of the Cop2 gene by RNA interference did not affect PSI accumulation in the alga (Ozawa et al, 2009). Interestingly, Ycf4 was also identified as a protein component of the eyespot in Chlamydomonas chloroplasts (Schmidt et al, 2006), possibly suggesting a second function of Ycf4 (in association with COP2) in the eyespot. Because embryophytes do not have eyespots, the data raise questions about the validity of the findings in Chlamydomonas for higher plants.…”

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The Plastid Genome-Encoded Ycf4 Protein Functions as a Nonessential Assembly Factor for Photosystem I in Higher Plants

et al. 2012

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Photosystem biogenesis in the thylakoid membrane is a highly complicated process that requires the coordinated assembly of nucleus-encoded and chloroplast-encoded protein subunits as well as the insertion of hundreds of cofactors, such as chromophores (chlorophylls, carotenoids) and iron-sulfur clusters. The molecular details of the assembly process and the identity and functions of the auxiliary factors involved in it are only poorly understood. In this work, we have characterized the chloroplast genome-encoded ycf4 (for hypothetical chloroplast reading frame no. 4) gene, previously shown to encode a protein involved in photosystem I (PSI) biogenesis in the unicellular green alga Chlamydomonas reinhardtii. Using stable transformation of the chloroplast genome, we have generated ycf4 knockout plants in the higher plant tobacco (Nicotiana tabacum). Although these mutants are severely affected in their photosynthetic performance, they are capable of photoautotrophic growth, demonstrating that, different from Chlamydomonas, the ycf4 gene product is not essential for photosynthesis. We further show that ycf4 knockout plants are specifically deficient in PSI accumulation. Unaltered expression of plastid-encoded PSI genes and biochemical analyses suggest a posttranslational action of the Ycf4 protein in the PSI assembly process. With increasing leaf age, the contents of Ycf4 and Y3IP1, another auxiliary factor involved in PSI assembly, decrease strongly, whereas PSI contents remain constant, suggesting that PSI is highly stable and that its biogenesis is restricted to young leaves.

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The Plastid Genome-Encoded Ycf4 Protein Functions as a Nonessential Assembly Factor for Photosystem I in Higher Plants

et al. 2012

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“…These clock-related proteins include the two subunits of the RNA binding protein CHLAMY1 (C1 and C3 subunits; Iliev et al, 2006), several Rhythm Of Chloroplast (ROC) proteins (Matsuo et al, 2008), Casein Kinase1 (CK1; Schmidt et al, 2006), and Constans (CO), which is also involved in photoperiodic signaling (Serrano et al, 2009). Among the ROCs are a number of putative transcription factors (ROC15, ROC40, ROC66, and ROC75), a putative subunit of E3 ubiquitin ligase (ROC114), and a protein of unknown function that contains leucine-rich repeats (ROC55).…”

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confidence: 99%

A Flavin Binding Cryptochrome Photoreceptor Responds to Both Blue and Red Light in Chlamydomonas reinhardtii

et al. 2012

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Cryptochromes are flavoproteins that act as sensory blue light receptors in insects, plants, fungi, and bacteria. We have investigated a cryptochrome from the green alga Chlamydomonas reinhardtii with sequence homology to animal cryptochromes and (6-4) photolyases. In response to blue and red light exposure, this animal-like cryptochrome (aCRY) alters the light-dependent expression of various genes encoding proteins involved in chlorophyll and carotenoid biosynthesis, light-harvesting complexes, nitrogen metabolism, cell cycle control, and the circadian clock. Additionally, exposure to yellow but not far-red light leads to comparable increases in the expression of specific genes; this expression is significantly reduced in an acry insertional mutant. These in vivo effects are congruent with in vitro data showing that blue, yellow, and red light, but not far-red light, are absorbed by the neutral radical state of flavin in aCRY. The aCRY neutral radical is formed following blue light absorption of the oxidized flavin. Red illumination leads to conversion to the fully reduced state. Our data suggest that aCRY is a functionally important blue and red light-activated flavoprotein. The broad spectral response implies that the neutral radical state functions as a dark form in aCRY and expands the paradigm of flavoproteins and cryptochromes as blue light sensors to include other light qualities.

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“…Members of the plastoglobulin family (also called fibrillin or PAP for plastid lipid-associated protein) [3], were the first known genuine plastoglobule protein components. In addition to vascular plants, plastoglobules are found in non-vascular species such as moss [4] and algae [5,6]. Interestingly, carotenoid-rich plastoglobule-like structures constitute the eyespot structure of Chlamydomonas reinhardtii, the proteome of which has been shown to contain members of the plastoglobulin family [6].…”

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Plastoglobules: versatile lipoprotein particles in plastids

Bréhélin

Kessler

Wijk

2007

Trends in Plant Science

243

157

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Plastoglobules are plastid-localized lipoprotein particles that contain tocopherols and other lipid isoprenoidderived metabolites, as well as structural proteins named plastoglobulins. Surprisingly, recent publications show that plastoglobules contain enzymes involved in the metabolism of these secondary metabolites, as well as enzymes of unknown function. The size and number of plastoglobules vary during plastid development and differentiation, and strongly increase during light stress, senescence and in mutants blocked in thylakoid formation. Given that plastoglobules are contiguous with the outer lipid leaflet of the thylakoid membrane, it is highly plausible that a function of plastoglobules is the active channeling of lipid molecules and lipid breakdown products. Understanding the function of plastoglobules should provide a foundation for improving the nutritional value and yield of plants.History of plastoglobule research and discovery Early electron microscopic studies revealed the presence of 'osmiophilic globuli' inside chloroplasts ( Figure 1) and chromoplasts, as well as other plastid types [1]. The diameter of these bodies, later termed plastoglobules, ranges from 30 nm to 5 mm. These plastoglobules could be conveniently isolated by flotation density centrifugation because of their relatively high lipid content [1,2]. The lipid composition of plastoglobules has been determined in several plant species -it consists mainly of prenyl-quinones and neutral lipids. Plastoglobules qualify as lipoprotein particles because they have been reported to associate with proteins. Members of the plastoglobulin family (also called fibrillin or PAP for plastid lipid-associated protein) [3], were the first known genuine plastoglobule protein components. In addition to vascular plants, plastoglobules are found in non-vascular species such as moss [4] and algae [5,6]. Interestingly, carotenoid-rich plastoglobule-like structures constitute the eyespot structure of Chlamydomonas reinhardtii, the proteome of which has been shown to contain members of the plastoglobulin family [6]. In cyanobacteria, the presence of 'lipid droplets' among the thylakoids has been reported [7]. The exact identity of these lipid droplets has not been defined; however, the presence of at least two plastoglobulin homologs in the genome of Synechocystis PCC6803 suggests that they could be plastoglobules.Although plastoglobules were largely viewed as passive lipid and carotenoid storage particles, their varying size in different species, plastid types and developmental stages suggested a more dynamic role. Moreover, correlative evidence suggested that plastoglobules are involved in thylakoid development as well as disassembly: (i) etioplasts with poorly developed thylakoids have more plastoglobules than are found in chloroplasts, but the plastoglobule abundance decreased during thylakoid biogenesis [8-10]; (ii) in senescent chloroplasts, during thylakoid disassembly, plastoglobules enlarge and accumulate [9,11,12]; (iii) several thylakoid biogenesis...

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Proteomic Analysis of the Eyespot ofChlamydomonas reinhardtiiProvides Novel Insights into Its Components and Tactic Movements

Cited by 176 publications

References 105 publications

The Plastid Genome-Encoded Ycf4 Protein Functions as a Nonessential Assembly Factor for Photosystem I in Higher Plants

The Plastid Genome-Encoded Ycf4 Protein Functions as a Nonessential Assembly Factor for Photosystem I in Higher Plants

A Flavin Binding Cryptochrome Photoreceptor Responds to Both Blue and Red Light in Chlamydomonas reinhardtii

Plastoglobules: versatile lipoprotein particles in plastids

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