Tritipyrum TtDHN3-TtLBD40 interaction conferred drought tolerance in wheat

Drought stress is a major threat that limits wheat productivity. In this study, the TtDHN3 gene was cloned from drought-tolerant Tritipyrum "Y1805" and transformed into common wheat "1718" using the coleoptile method. TtDHN3 expression levels in "Y1805" and the overexpression (OE) lines were upregulated under drought stress. After 24 h drought stress, TtDHN3 OE line showed significantly less leaf wilting compared with wild-type plants. At each experimental period, root length, shoot height, stem diameter, and fresh and dry weight of the roots and shoots in the OE lines were significantly higher than in wild-type plants. TtDHN3 OE significantly increased the activities of superoxide dismutase and catalase, enhanced the levels of soluble sugars, proline, chlorophylls, and carotenoids, and reduced malondialdehyde content and relative electrical conductivity under drought stress. In contrast, TtDHN3-silenced plants exhibited the opposite trends. Yeast two-hybrid assays suggested that TtDHN3 interacted with TtLBD40. This interaction was further confirmed by bimolecular fluorescence complementation and co-immunoprecipitation assays. Phenotypic and physiological-biochemical analyses demonstrated that TtLBD40 played a positive regulatory role in wheat drought responses. In summary, the interaction between TtDHN3 and TtLBD40 might enhance drought tolerance by improving osmotic regulation and reactive oxygen species scavenging. This study thus provides valuable genetic resources and a theoretical foundation for the molecular breeding of drought-tolerant wheat.