High non‐photochemical quenching of VPZ transgenic potato plants limits CO₂ assimilation under high light conditions and reduces tuber yield under fluctuating light

Abstract

Under natural conditions, photosynthesis has to be adjusted to fluctuating light intensities. Leaves exposed to high light dissipate excess light energy in form of heat at photosystem II (PSII) by a process called non-photochemical quenching (NPQ). Upon fast transition from light to shade, plants lose light energy by a relatively slow relaxation from photoprotection. Combined overexpression of violaxanthin deepoxidase (VDE), photosystem II subunit S (PsbS) and zeaxanthin epoxidase (ZEP) in tobacco accelerates relaxation from photoprotection, and increases photosynthetic productivity. In Arabidopsis, expression of the same three genes (VPZ) resulted in a more rapid photoprotection but growth of the transgenic plants was impaired. Here we report on VPZ expressing potato plants grown under various light regimes. Similar to tobacco and Arabidopsis, induction and relaxation of NPQ was accelerated under all growth conditions tested, but, did not cause an overall increased photosynthetic rate or growth of transgenic plants. Tuber yield of VPZ expressing plants was unaltered as compared to control plants under constant light conditions and even decreased under fluctuating light conditions. Under control conditions, levels of the

Modulation of xanthophyll cycle impacts biomass productivity in the marine microalgaNannochloropsis

“…However, when metabolic engineering is applied to photosynthesis, the complexity of the environmental conditions of the intended cultivation system should also be considered, as well as the physiology of the species targeted for improvement. For instance, in plants of Nicotiana benthamiana, Arabidopsis thaliana and Solanum tuberosum , VDE, ZEP and PSBS overexpression did not show the same effects (47, 48), indicating that species-specific physiological or morphological features are highly influential on the homeostasis of the photosynthetic metabolism. In the environment of photobioreactors, most of the culture is light limited, while only a small layer of cells is exposed to full sunlight.…”

The impact of long‐term acclimation to different growth light intensities on the regulation of zeaxanthin epoxidase in different plant species

“…In particular, the reconversion of Zx to violaxanthin (Vx) is known to limit the kinetics of the deactivation of qE (Ruban & Horton, 1999; Ruban & Johnson, 2010). Consequently, over‐expression of ZEP has been successfully applied to accelerate qE relaxation under fluctuating light in tobacco (Kromdijk et al, 2016), Arabidopsis (Garcia‐Molina & Leister, 2020) and potato (Lehretz et al, 2022) plants. Long‐lasting HL stress is known to induce photoinhibition of PSII (Krause, 1988; Powles, 1984).…”

Plethora of QTLs found inArabidopsis thalianareveals complexity of genetic variation for photosynthesis in dynamic light conditions

“…Accelerating the NPQ relaxation in tobacco and soybean has been shown to result in 15% and 30% higher yields respectively (Kromdijk et al ., 2016; De Souza et al ., 2022). The same approach in Arabidopsis thaliana and potato did not result in accelerated NPQ relaxation or changes in yields, showing that it is not a one-size-fits-all solution (Garcia-Molina and Leister, 2020; Lehretz et al ., 2022). Despite the relative absence of natural genetic variation in the core photosynthetic machinery, there is ample phenotypic variation for photosynthesis, implying there is standing genetic variation outside the core machinery.…”