Functional characterization of the quinoa transcription factor CqBBX28 in drought stress response

This study investigated the role of the transcription factor gene CqBBX28 in quinoa drought tolerance. Although associated with drought response, its functional mechanism remained unclear. We employed homologous recombination and virus-induced gene silencing (VIGS) to generate overexpression (OE) callus lines and silenced plants, respectively. Under drought stress, OE callus lines showed significantly increased fresh weight and proline content but decreased malondialdehyde (MDA) levels compared to wild-type (WT). Furthermore, T3 transgenic Arabidopsis plants overexpressing CqBBX28 exhibited enhanced drought tolerance. These findings clarify the function of CqBBX28 and provide a valuable genetic resource for improving crop drought resistance. Under drought stress, the OE lines showed significantly higher seed germination rate, seedling fresh weight, root length, Relative Water Content (RWC), Net Photosynthetic Rate (Pn), Transpiration Rate (Tr), Stomatal Conductance (Gs), chlorophyll content, antioxidant enzyme activities, and Proline content compared to the WT. The expression levels of seven stress-related genes, including AtRD22, were also significantly elevated in the OE lines. Notably, the expression of AtDREB1A was 11.03-fold higher than in the WT. Conversely, Intercellular CO₂ Concentration (Ci), Reactive Oxygen Species (ROS) levels, Malondialdehyde (MDA) content, and relative electrical conductivity were significantly lower in the OE lines. Additionally, under drought stress, silenced lines displayed reduced drought tolerance, with significantly lower leaf relative water content, Pn, Tr, Gs, chlorophyll content, antioxidant enzyme activities, and Pro content compared to the WT. These findings provide an important theoretical basis for stress resistance breeding in quinoa and also offer a valuable drought tolerance gene resource for the breeding of other crops.