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Akhtar TA, Surowiecki P, Siekierska H, Kania M, Van Gelder K, Rea KA, Virta LKA, Vatta M, Gawarecka K, Wojcik J, Danikiewicz W, Buszewicz D, Swiezewska E, Surmacz L. Polyprenols Are Synthesized by a Plastidial cis-Prenyltransferase and Influence Photosynthetic Performance. Plant Cell 2017; 29:1709-1725. [PMID: 28655749 PMCID: PMC5559739 DOI: 10.1105/tpc.16.00796] [Citation(s) in RCA: 30] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/15/2016] [Revised: 05/18/2017] [Accepted: 06/24/2017] [Indexed: 05/22/2023]
Abstract
Plants accumulate a family of hydrophobic polymers known as polyprenols, yet how they are synthesized, where they reside in the cell, and what role they serve is largely unknown. Using Arabidopsis thaliana as a model, we present evidence for the involvement of a plastidial cis-prenyltransferase (AtCPT7) in polyprenol synthesis. Gene inactivation and RNAi-mediated knockdown of AtCPT7 eliminated leaf polyprenols, while its overexpression increased their content. Complementation tests in the polyprenol-deficient yeast ∆rer2 mutant and enzyme assays with recombinant AtCPT7 confirmed that the enzyme synthesizes polyprenols of ∼55 carbons in length using geranylgeranyl diphosphate (GGPP) and isopentenyl diphosphate as substrates. Immunodetection and in vivo localization of AtCPT7 fluorescent protein fusions showed that AtCPT7 resides in the stroma of mesophyll chloroplasts. The enzymatic products of AtCPT7 accumulate in thylakoid membranes, and in their absence, thylakoids adopt an increasingly "fluid membrane" state. Chlorophyll fluorescence measurements from the leaves of polyprenol-deficient plants revealed impaired photosystem II operating efficiency, and their thylakoids exhibited a decreased rate of electron transport. These results establish that (1) plastidial AtCPT7 extends the length of GGPP to ∼55 carbons, which then accumulate in thylakoid membranes; and (2) these polyprenols influence photosynthetic performance through their modulation of thylakoid membrane dynamics.
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Affiliation(s)
- Tariq A Akhtar
- Department of Molecular and Cellular Biology, University of Guelph, Guelph, Ontario N1G 2W1, Canada
| | - Przemysław Surowiecki
- Institute of Biochemistry and Biophysics, Polish Academy of Sciences, 02-106 Warsaw, Poland
| | - Hanna Siekierska
- Institute of Biochemistry and Biophysics, Polish Academy of Sciences, 02-106 Warsaw, Poland
| | - Magdalena Kania
- Institute of Organic Chemistry, Polish Academy of Sciences, 01-224 Warsaw, Poland
| | - Kristen Van Gelder
- Department of Molecular and Cellular Biology, University of Guelph, Guelph, Ontario N1G 2W1, Canada
| | - Kevin A Rea
- Department of Molecular and Cellular Biology, University of Guelph, Guelph, Ontario N1G 2W1, Canada
| | - Lilia K A Virta
- Department of Molecular and Cellular Biology, University of Guelph, Guelph, Ontario N1G 2W1, Canada
| | - Maritza Vatta
- Department of Molecular and Cellular Biology, University of Guelph, Guelph, Ontario N1G 2W1, Canada
| | - Katarzyna Gawarecka
- Institute of Biochemistry and Biophysics, Polish Academy of Sciences, 02-106 Warsaw, Poland
| | - Jacek Wojcik
- Institute of Biochemistry and Biophysics, Polish Academy of Sciences, 02-106 Warsaw, Poland
| | - Witold Danikiewicz
- Institute of Organic Chemistry, Polish Academy of Sciences, 01-224 Warsaw, Poland
| | - Daniel Buszewicz
- Institute of Biochemistry and Biophysics, Polish Academy of Sciences, 02-106 Warsaw, Poland
| | - Ewa Swiezewska
- Institute of Biochemistry and Biophysics, Polish Academy of Sciences, 02-106 Warsaw, Poland
| | - Liliana Surmacz
- Institute of Biochemistry and Biophysics, Polish Academy of Sciences, 02-106 Warsaw, Poland
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Zientara-Rytter K, Lukomska J, Moniuszko G, Gwozdecki R, Surowiecki P, Lewandowska M, Liszewska F, Wawrzyńska A, Sirko A. Identification and functional analysis of Joka2, a tobacco member of the family of selective autophagy cargo receptors. Autophagy 2011; 7:1145-58. [PMID: 21670587 PMCID: PMC3242614 DOI: 10.4161/auto.7.10.16617] [Citation(s) in RCA: 109] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2010] [Revised: 05/26/2011] [Accepted: 05/27/2011] [Indexed: 12/27/2022] Open
Abstract
Two main mechanisms of protein turnover exist in eukaryotic cells: the ubiquitin-proteasome system and the autophagy-lysosomal pathway. Autophagy is an emerging important constituent of many physiological and pathological processes, such as response to nutrient deficiency, programmed cell death and innate immune response. In mammalian cells the selectivity of autophagy is ensured by the presence of cargo receptors, such as p62/SQSTM1 and NBR1, responsible for sequestration of the ubiquitinated proteins. In plants no selective cargo receptors have been identified yet. The present report indicates that structural and functional homologs of p62 and NBR1 proteins exist in plants. The tobacco protein, named Joka2, has been identified in yeast two-hybrid search as a binding partner of a small coiled-coil protein, a member of UP9/LSU family of unknown function, encoded by the UP9C gene strongly and specifically induced during sulfur deficiency. The typical domains of p62 and NBR1 are conserved in Joka2. Similarly to p62, Joka2-YFP has dual localization (cytosolic speckles and the nucleus); it forms homodimers and interacts with a member of the ATG8 family. Increased expression of Joka2 and ATG8f was observed in roots of tobacco plants grown for two days in nutrient-deficient conditions. Constitutive ectopic expression of Joka2-YFP in tobacco resulted in attenuated response (manifested by lesser yellowing of the leaves) to nutrient deficiency. In conclusion, Joka2, and presumably the process of selective autophagy, might constitute an important part of plant response to environmental stresses.
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