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Biswal AK, Pattanayak GK, Ruhil K, Kandoi D, Mohanty SS, Leelavati S, Reddy VS, Govindjee G, Tripathy BC. Reduced expression of chlorophyllide a oxygenase (CAO) decreases the metabolic flux for chlorophyll synthesis and downregulates photosynthesis in tobacco plants. PHYSIOLOGY AND MOLECULAR BIOLOGY OF PLANTS : AN INTERNATIONAL JOURNAL OF FUNCTIONAL PLANT BIOLOGY 2024; 30:1-16. [PMID: 38435853 PMCID: PMC10901765 DOI: 10.1007/s12298-023-01395-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/12/2023] [Revised: 11/17/2023] [Accepted: 11/20/2023] [Indexed: 03/05/2024]
Abstract
Chlorophyll b is synthesized from chlorophyllide a, catalyzed by chlorophyllide a oxygenase (CAO). To examine whether reduced chlorophyll b content regulates chlorophyll (Chl) synthesis and photosynthesis, we raised CAO transgenic tobacco plants with antisense CAO expression, which had lower chlorophyll b content and, thus, higher Chl a/b ratio. Further, these plants had (i) lower chlorophyll b and total Chl content, whether they were grown under low or high light; (ii) decreased steady-state levels of chlorophyll biosynthetic intermediates, due, perhaps, to a feedback-controlled reduction in enzyme expressions/activities; (iii) reduced electron transport rates in their intact leaves, and reduced Photosystem (PS) I, PS II and whole chain electron transport activities in their isolated thylakoids; (iv) decreased carbon assimilation in plants grown under low or high light. We suggest that reduced synthesis of chlorophyll b by antisense expression of CAO, acting at the end of Chl biosynthesis pathway, downregulates the chlorophyll b biosynthesis, resulting in decreased Chl b, total chlorophylls and increased Chl a/b. We have previously shown that the controlled up-regulation of chlorophyll b biosynthesis and decreased Chl a/b ratio by over expression of CAO enhance the rates of electron transport and CO2 assimilation in tobacco. Conversely, our data, presented here, demonstrate that-antisense expression of CAO in tobacco, which decreases Chl b biosynthesis and increases Chl a/b ratio, leads to reduced photosynthetic electron transport and carbon assimilation rates, both under low and high light. We conclude that Chl b modulates photosynthesis; its controlled down regulation/ up regulation decreases/ increases light-harvesting, rates of electron transport, and carbon assimilation. Supplementary Information The online version contains supplementary material available at 10.1007/s12298-023-01395-5.
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Affiliation(s)
- Ajaya K. Biswal
- School of Life Sciences, Jawaharlal Nehru University, New Delhi, 110067 India
| | - Gopal K. Pattanayak
- School of Life Sciences, Jawaharlal Nehru University, New Delhi, 110067 India
| | - Kamal Ruhil
- School of Life Sciences, Jawaharlal Nehru University, New Delhi, 110067 India
| | - Deepika Kandoi
- School of Life Sciences, Jawaharlal Nehru University, New Delhi, 110067 India
- Department of Life Sciences, Sharda University, Greater Noida, UP, India
| | - Sushree S. Mohanty
- School of Life Sciences, Jawaharlal Nehru University, New Delhi, 110067 India
| | - Sadhu Leelavati
- International Center for Genetic Engineering and Biotechnology, New Delhi, 110067 India
| | - Vanga S. Reddy
- International Center for Genetic Engineering and Biotechnology, New Delhi, 110067 India
| | - Govindjee Govindjee
- School of Life Sciences, Jawaharlal Nehru University, New Delhi, 110067 India
- Department of Plant Biology, Department of Biochemistry, and Center of Biophysics & Quantitative Biology, University of Illinois at Urbana-Champaign, Urbana, IL 61801 USA
| | - Baishnab C. Tripathy
- School of Life Sciences, Jawaharlal Nehru University, New Delhi, 110067 India
- Department of Biotechnology, Sharda University, Greater Noida, UP 201310 India
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Kandoi D, Ruhil K, Govindjee G, Tripathy BC. Overexpression of cytoplasmic C 4 Flaveria bidentis carbonic anhydrase in C 3 Arabidopsis thaliana increases amino acids, photosynthetic potential, and biomass. PLANT BIOTECHNOLOGY JOURNAL 2022; 20:1518-1532. [PMID: 35467074 PMCID: PMC9342616 DOI: 10.1111/pbi.13830] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/09/2021] [Revised: 04/15/2022] [Accepted: 04/18/2022] [Indexed: 05/20/2023]
Abstract
An important method to improve photosynthesis in C3 crops, such as rice and wheat, is to transfer efficient C4 characters to them. Here, cytosolic carbonic anhydrase (CA: βCA3) of the C4 Flaveria bidentis (Fb) was overexpressed under the control of 35 S promoter in Arabidopsis thaliana, a C3 plant, to enhance its photosynthetic efficiency. Overexpression of CA resulted in a better supply of the substrate HCO3- for the endogenous phosphoenolpyruvate carboxylase in the cytosol of the overexpressers, and increased its activity for generating malate that feeds into the tricarboxylic acid cycle. This provided additional carbon skeleton for increased synthesis of amino acids aspartate, asparagine, glutamate, and glutamine. Increased amino acids contributed to higher protein content in the transgenics. Furthermore, expression of FbβCA3 in Arabidopsis led to a better growth due to expression of several genes leading to higher chlorophyll content, electron transport, and photosynthetic carbon assimilation in the transformants. Enhanced CO2 assimilation resulted in increased sugar and starch content, and plant dry weight. In addition, transgenic plants had lower stomatal conductance, reduced transpiration rate, and higher water-use efficiency. These results, taken together, show that expression of C4 CA in the cytosol of a C3 plant can indeed improve its photosynthetic capacity with enhanced water-use efficiency.
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Affiliation(s)
- Deepika Kandoi
- School of Life SciencesJawaharlal Nehru UniversityNew DelhiIndia
| | - Kamal Ruhil
- School of Life SciencesJawaharlal Nehru UniversityNew DelhiIndia
| | - Govindjee Govindjee
- Department of Plant BiologyDepartment of Biochemistry, and Center of Biophysics & Quantitative BiologyUniversity of Illinois at Urbana‐ChampaignUrbanaILUSA
| | - Baishnab C. Tripathy
- School of Life SciencesJawaharlal Nehru UniversityNew DelhiIndia
- Department of BiotechnologySharda UniversityGreater NoidaUPIndia
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Mohapatra A, Tripathy BC. Differential distribution of chlorophyll biosynthetic intermediates in stroma, envelope and thylakoid membranes in Beta vulgaris. PHOTOSYNTHESIS RESEARCH 2007; 94:401-10. [PMID: 17638115 DOI: 10.1007/s11120-007-9209-6] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/03/2007] [Accepted: 05/28/2007] [Indexed: 05/16/2023]
Abstract
Stroma, envelope and thylakoid membranes were prepared from chloroplasts isolated from leaves of Beta vulgaris. Out of total plastidic protochlorophyllide, envelope membranes contained 1.5%, thylakoids had the maximum 98.48% and stroma had a trace fraction of 0.02%. Distribution of the Mg-protoporphyrin IX and its monoester was 89.0% in thylakoids, 10.0% in stroma and 1.0% in envelope. A substantial fraction (33.77%) of plastidic protoporphyrin IX was partitioned into stroma. Envelope contained 0.66% and thylakoids had 65.57% of the total plastidic protoporphyrin IX pool. The proportion of monovinyl and divinyl forms of protochlorophyllide was almost similar in intact plastid, thylakoids, and outer and inner envelope membranes suggesting a tight regulation of vinyl reductase enzyme. The significance of differential distribution of chlorophyll biosynthetic intermediates among thylakoids, envelope and stroma is discussed.
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Affiliation(s)
- Anasuya Mohapatra
- School of Life Sciences, Jawaharlal Nehru University, New Delhi, 110067, India
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