The Role of the Organization of Light-Harvesting Complex II in the Drought Sensitivity of Pisum sativum L.

Drought stress is a major abiotic factor limiting plant growth and productivity. This study investigates the role of oligomerization of the light-harvesting complex of photosystem II (LHCII) in modulating plant responses to drought stress. Using pea plants (Pisum sativum L.): Borec (wild type) and its mutants Costata 2/133 and Coeruleovireus 2/16, with different degrees of LHCII oligomerization, we examined the impact of water deficit on the functions of the photosynthetic apparatus. This study demonstrated that plants with a higher degree of LHCII oligomerization (wild type and Coeruleovireus 2/16) have enhanced drought tolerance, expressed by reduced lipid peroxidation and membrane damage, protection of the photosynthetic pigment content, which corresponds with better photosynthetic performance. Data revealed only minor drought-induced inhibition of photosystem II (PSII) photochemistry (Fv/Fm, ΦPSII), electron transport rate (ETR), and rate of photosynthesis (RFd)), along with sustained performance indices (PIABS and PItotal) in plants with higher LHCII oligomerization compared to those with lower levels (Costata 2/133). Additionally, the current study indicates that under drought stress and low actinic light, the interaction with plastoquinone and controlled dissipation of excess energy are promoted in thylakoid membranes with increased LHCII oligomerization. In contrast, drought-stressed plants with lower oligomerization (Costata 2/133) showed a significant increase in non-regulated energy losses under high actinic light. These results highlight the protective function of LHCII oligomerization in preserving photosynthetic integrity and functioning under drought stress and suggest that it could be a promising target for enhancing crop resilience in a changing climate.