Integrative Physiological, Transcriptomic, and Functional Analysis Reveals a Positive Contribution of TaCDPK22-5A to Drought Adaptation in Wheat
Background: Drought tolerance in wheat is a complex trait controlled by multiple regulatory networks, among which calcium-dependent protein kinases (CDPKs) act as important components linking stress perception with downstream cellular responses. However, the functional contribution of individual CDPK members to drought adaptation in wheat remains largely unclear. This study aimed to identify and functionally characterize drought-responsive CDPK genes associated with differential drought responses in wheat. Methods: Two wheat lines derived from the same breeding background exhibiting contrasting drought adaption, 23B1 and 23B39, were subjected to PEG6000-induced osmotic stress. Growth traits, osmotic adjustment-related metabolites, membrane damage indicators, and antioxidant enzyme activity were evaluated. Transcriptomic analysis was performed at early drought-response stages, followed by differential expression analysis, functional enrichment, CDPK family screening, and qRT-PCR validation. The role of TaCDPK22-5A was further investigated using barley stripe mosaic virus (BSMV)-mediated virus-induced gene silencing (VIGS). Results: The drought-responsive line 23B1 maintained stronger growth, accumulated higher levels of proline and soluble sugars, exhibited enhanced peroxidase activity, and showed reduced membrane lipid peroxidation compared with 23B39. Transcriptome analysis revealed extensive transcriptional reprogramming under drought stress, with differentially expressed genes mainly associated with metabolic adjustment, transport regulation, secondary metabolism, and stress-responsive pathways. Among the identified CDPK members, TaCDPK22-5A showed a strong drought-responsive expression pattern in the line exhibiting stronger drought tolerance (23B1). Virus-induced gene silencing of TaCDPK22-5A significantly impaired drought tolerance, resulting in reduced growth, biomass accumulation, and chlorophyll retention under drought conditions. Conclusions: These findings demonstrate that TaCDPK22-5A contributes positively to drought adaptation in wheat and highlight CDPK-mediated calcium signaling as an important regulatory component of drought responses. The identified gene provides a potential target for improving drought resilience in wheat breeding.