Partial Suppression of the Proline Dehydrogenase Gene Mitigates the Impact of Drought on the Photosynthetic Apparatus and Productivity in Winter Wheat

Water scarcity severely constrains the genetic potential of wheat yield worldwide. Proline is among the most versatile stress-related metabolites in plants, and targeting genes involved in proline synthesis and degradation represents a promising strategy for developing drought-tolerant wheat genotypes. This study evaluates the performance of the photosynthetic apparatus in transgenic wheat line with RNAi-mediated suppression of proline dehydrogenase (ProDH) and in the original (wild-type) genotype, under both drought and recovery conditions. Drought was induced at the flowering stage by lowering soil moisture to 30% field capacity for 7 days, compared with 70% field capacity in control plants. Measurements were taken at the onset and end of drought period and 7 days after subsequent recovery. The results demonstrated that drought-treated transgenic plants exhibited improved responses to both the short-term and prolonged effects of stress. Relative water content and chlorophyll levels in the leaves of the transgenic plants changed to a significantly lesser extent. The CO₂ assimilation rate in the leaves of transgenic plants was significantly higher than in the wild type under both drought stress and recovery. The transgenic plants also showed superior water-use efficiency during photosynthesis under both conditions. While superoxide dismutase and ascorbate peroxidase activities in leaf chloroplasts increased similarly in both genotypes under drought, they returned to control levels more rapidly in the transgenic plants during recovery. Drought-induced productivity reduction was also significantly lower in the transgenic plants. These findings suggest that RNAi-mediated suppression of ProDH improved photosynthetic performance and grain yield in wheat under drought conditions.