Characterization of PetM cytochrome b6f subunit 7 domain-containing protein in tomato

Abstract

In recent years, multiple advances have been made in understanding the photosynthetic machinery in model organisms. Knowledge transfer to horticultural important fruit crops is challenging and time-consuming due to restrictions in gene editing tools and prolonged life cycles. Here, we characterize a gene encoding a PetM domain-containing protein in tomato. The CRISPR/Cas9 knockout lines of the PetM showed impairment in the chloroplastic electron transport rate (ETR), reduced CO₂ assimilation, and reduction of carotenoids and chlorophylls (Chl) under several light conditions. Further, growth-condition-dependent elevation or repression of Chl a/b ratios and de-epoxidation states were identified, underlining possible impairment compensation mechanisms. However, under low light and glasshouse conditions, there were basal levels in CO₂ assimilation and ETR, indicating a potential role of the PetM domain in stabilizing the cytochrome b6f complex (C b6f) under higher light irradiance and increasing its quantum efficiency. This suggests a potential evolutionary role in which this domain might stabilize the site of the C b6f regulating ratios of cyclic and linear electron transport and its potential importance during the conquest of terrestrial ecosystems during which plants were exposed to higher irradiance. Finally, the results are discussed with regard to metabolism and their implication to photosynthesis from an agronomic perspective.

Acknowledgements

We would like to thank Dr. Micha Wijesingha Ahchige for guiding and giving advice for the CRISPR/Cas9 vector generation and Dr. Mark A. Schoettler and Dr. Ryo Yokohama for the scientific advices and discussions. Also thanks to Dr. Karin Köhl, the greenhouse team of the Max Planck Institute of Molecular Plant Physiology, for transforming and handling the plants. M.B. appreciates the financial support of the International Max Planck Research School for Molecular Plant Sciences (IMPRS-MolPlant). The research fellowship granted by Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq-Brazil) to A.N.-N. is gratefully acknowledged. A.R.F. and S.A. acknowledge the European Union’s Horizon 2020 research and innovation programme, project PlantaSYST (SGA-CSA No. 739582 under FPA No. 664620), and the BG05M2OP001-1.003-001-C01 project, financed by the European Regional Development Fund through the Bulgarian’ Science and Education for Smart Growth’ Operational Programme. S.A. acknowledges the EU Horizon 2020, call HORIZON-WIDERA-2022-TALENTS-01, project NatGenCrop (grant agreement No. 101087091).

Authors’ contribution

M.B., S.A. and A.R.F. designed the experiment. M.B. performed the experiments and data analysis. M.B., A.R.F. and S.A. wrote the manuscript. A.N.-N. reviewed the manuscript.

Data availability

The authors declare that all the data supporting the findings of this study are available within the paper and its supporting information files.

Conflict of interests statement

The authors declare no conflict of interest.

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