Biology subjects

Tanigawa, K.

Publications and source records attributed to Tanigawa, K..

3 recordsLinked to original sources

bioRxiv2026

Moderate overexpression of PROTON GRADIENT REGULATION 5 improves photosynthetic performance and plant growth under fluctuating low light in Arabidopsis thaliana

Cyclic electron transport (CET) around photosystem I (PSI) is essential for maintaining photosynthetic efficiency by balancing ATP/NADPH production and protecting PSI from photoinhibition. Although the PROTON GRADIENT REGULATION 5 (PGR5)-dependent CET pathway is known to be critical under high or fluctuating light conditions, its role under fluctuating low light remains poorly understood. In natural environments, plants frequently experience prolonged low irradiance interspersed with brief sunflecks, making fluctuating low light a physiologically relevant condition. Here, we investigated Arabidopsis thaliana lines with graded PGR5 expression levels to evaluate the dose-dependent contribution of PGR5 to CET activity, photosynthetic regulation, and growth performance under both low light and fluctuating low light conditions. Moderate increase in the PGR5 protein level enhanced CET activity, accelerated photosynthetic induction, improved PSI protection and increased biomass accumulation under fluctuating low light. In contrast, excessive PGR5 accumulation impaired photosynthetic performance and reduced plant growth, indicating that optimal CET capacity requires precise tuning of PGR5 abundance. These results reveal a non-linear relationship between PGR5 protein levels and photosynthetic performance and demonstrate that moderate enhancement of CET improves plant productivity under fluctuating low light. Our findings highlight the importance of optimizing CET capacity to match dynamic light environments and suggest that fine-tuning PGR5 expression could be a promising strategy for improving crop performance under natural canopy conditions. Significance statementModerate increase in the PGR5 improves plant productivity, whereas excessive PGR5 accumulation impaired photosynthetic performance and reduced plant growth. Therefore, optimizing CET capacity by the fine-tuning PGR5 expression is important for improving crop productivity.

plant biology↗

bioRxiv2025

Far-Red Light in Early Growth Stages Boosts Lettuce Biomass and Preserves Anthocyanins

Background and AimsLight plays a dual role in plants, serving as both an energy source and a regulator of development from seedling to senescence. Recently, far-red (FR) radiation has gained attention in the controlled environment agriculture (CEA) science and grower community for its potential to enhance yield through canopy expansion and improved light capture, contributing positively to photosynthesis. This study explores how supplemental FR light promotes lettuce growth and morphology across weekly intervals as well as analyzing photosynthetic parameters, pigment accumulation, and anthocyanin gene expression. MethodsRed leaf lettuce (Lactuca sativa Red Fire) was grown in a commercial plant factory with artificial light for six weeks. 5000K white (W) light was maintained at 300 mol m-2 s-1, and FR, when supplemented, was added at 100 mol m-2 s-1 in addition to the 300 mol m-2 s-1 of W light. Four lighting treatments were tested under a 16 h photoperiod: (1) W for all 6 weeks ("W"), (2) 4 weeks of W followed by 2 weeks of supplemental FR ("W to W+FR"), (3) 4 weeks of FR supplementation followed by 2 weeks of only W ("W+FR to W"), and (4) W+FR for all 6 weeks ("W+FR"). Key ResultsThe shoot dry weight after 6 weeks in "W+FR", "W+FR to W" and "W to W+FR" was greater than "W". Both "W+FR" and "W+FR to W" showed a tendency for greater canopy expansion compared to "W" as well as "W to W+FR". There were no significant differences in stomatal conductance among the treatments. On the other hand, in both "W" and "W+FR to W" plants, CO2 assimilation rates were enhanced when FR light was supplemented during measurement, compared to when FR was not provided. Anthocyanin accumulation was greater in both "W" and "W+FR to W", consistent with the expression of key genes involved in the anthocyanin biosynthesis pathway, including anthocyanin synthase (ANS), flavanone 3-hydroxylase (F3H) and dihydroflavonol 4-reductase (DFR). ConclusionsThis study demonstrates that FR supplementation during the early growth stages of lettuce promotes biomass accumulation by enhancing both canopy expansion and photosynthetic activity, while maintaining high levels of functional compounds such as anthocyanins.

physiology↗

bioRxiv2025

Cyt b6/f Complex Fine-Tunes PSI Stability and Photosynthetic Capacity Under Fluctuating Light

Plants encounter dynamic light fluctuations in natural habitats, requiring robust mechanisms to protect Photosystem I (PSI) against photoinhibition. The cytochrome (Cyt) b6/f complex plays a pivotal role in regulating electron flow and ensuring PSI stability under fluctuating light. However, its precise role in balancing PSI protection and photosynthetic capacity remains unclear. In this study, transgenic tobacco (Nicotiana tabacum L. W38) with reduced Cyt b6/f content was used to examine PSI tolerance to photoinhibition and photosynthetic performance under fluctuating light. Notably, the reduced Cyt b6/f content conferred significant protection of PSI against photoinhibition induced by fluctuating light, albeit at the expense of the electron transport capacity. Remarkably, PSI stability was maintained even under extreme fluctuating light conditions in the plants with lowest Cyt b6/f contents, highlighting a trade-off between photoprotection and photosynthetic capacity. These findings reveal that a reduction in Cyt b6/f content enhances PSI protection while adjusting electron transport capacity, making plants more adaptable in environments dominated by low light and transient sunflecks. This study provides new insights into the adaptive strategies of plants under dynamic light environments and underscores the potential of targeting Cyt b6/f for enhancing crop tolerance to fluctuating light conditions.

plant biology↗