Abstract Carotenoids are important isoprenoids produced in the plastids of photosynthetic organisms that play key roles in photoprotection and antioxidative processes. β-carotene is generated from lycopene by the lycopene β-cyclase (LCYB). Previously, we demonstrated that the introduction of the Daucus carota (carrot) DcLCYB1 gene into tobacco (cultivar Xanthi) resulted in increased levels of abscisic acid (ABA) and especially gibberellins (GAs), resulting in increased plant yield. In order to understand this phenomenon prior exporting this genetic strategy to crops, we generated tobacco (cultivar Petit Havana) mutants that exhibited a wide range of LCYB expression. Transplastomic plants expressing DcLCYB1 at high levels showed a wild-type-like growth, even though their pigment content was increased, and their leaf GA content was reduced. RNAi NtLCYB lines showed different reductions in NtLCYB transcript abundance, correlating with reduced pigment content and plant variegation. Photosynthesis (leaf absorptance, Fv/Fm, and ETRII) and plant growth were impaired. Remarkably, drastic changes in phytohormone content also occurred in the RNAi lines. However, external application of phytohormones was not sufficient to rescue their phenotypes, suggesting that altered photosynthetic efficiency might be another important factor explaining their reduced biomass. These results show that LCYB expression influences plant biomass by different mechanisms and suggests thresholds for LCYB expression levels that might be beneficial/detrimental for plant growth.
|Original language||English (US)|
|Journal||Journal of Experimental Botany|
|State||Published - Jan 23 2021|
Bibliographical noteKAUST Repository Item: Exported on 2021-01-28
Acknowledgements: We are extremely grateful to Dr. Aleksandra Skirycz for supporting an independent research project to be completed in her research group at the Max-Planck-Institut für Molekulare Pflanzenphysiologie (MPI-MP). Dr. Daniel Karcher (MPI-MP), kindly provided the constructs pDK325 and pDK326 used for generation of pJM36 and pJM37 transplastomic vectors. We are grateful to Prof. Dr. Lothar Willmitzer for his great support and advice, and the MPI-MP and the head of the Green Team Dr. Karin Köhl and its members (Britta Hausmann, Florian Hundert, Dirk Zerning and Laura Westpahl) for plant cultivation. The gibberellin measurements were supported by a European Regional Development Fund Project “Centre for Experimental Plant Biology” (No. CZ.02.1.01/0.0/0.0/16_019/0000738) and the Czech Science Foundation (18-10349S).