Flavodiiron Proteins Increase Plant Biomass Under Fluctuating Light and Enhance Chilling Tolerance in Tobacco

The introduction of flavodiiron (FLV) proteins in angiosperms can modulate photosynthesis and photoprotection under fluctuating light conditions. However, the potential of FLV in crop improvement and chilling tolerance remains poorly understood. To address this, transgenic tobacco plants expressing the FLVA and FLVB genes from Physcomitrium patens were used to examine the influence of FLV on plant biomass and chilling tolerance. The results indicated that the steady-state CO₂ assimilation rate (A_N) was not altered by the introduction of FLV. However, during shade-sun transitions, FLV lines exhibited higher stomatal conductance and A_N compared to wild-type (WT) plants. Consequently, plant biomass under fluctuating light significantly increased by 21% in FLV Line 8 compared to WT plants. Furthermore, stomatal density, leaf mass per area and leaf nitrogen content per area were significantly enhanced in Line 8 plants. Even though some variability between lines presents, these results suggest that FLV can regulate plant growth through multiple effects on leaf physiology. At chilling temperature and high light, the over-reduction of the photosynthetic electron transfer chain was significantly mitigated in FLV lines compared to WT plants, thereby reducing chilling-induced photoinhibition of photosystem I and II. These results provide insights into the potential application of FLV in crop improvement.