DoSPR1-2 links cortical microtubule remodeling with drought-stress responses in Dalbergia odorifera

Drought severely restricts the establishment and growth of tropical woody plants, yet the cytoskeletal mechanisms underlying their drought responses remain poorly understood. Dalbergia odorifera is an economically and ecologically important tropical tree, but the molecular components linking cortical microtubule remodeling with drought-stress responses in this species have not been characterized. SPIRAL1 (SPR1) is a plant-specific microtubule-associated protein; however, the functions of SPR1 homologs in drought-responsive woody plants remain largely unknown. Transcriptome profiling identified DoSPR1-2 as a drought-responsive SPR1 -family gene in D. odorifera . DoSPR1-2 transcript abundance decreased in leaves but increased at several time points in roots. Transient elevation of DoSPR1-2 expression was associated with reduced drought tolerance in OE seedlings, as evidenced by more pronounced wilting, stronger DAB and NBT staining, and elevated malondialdehyde content, peroxidase activity, and electrolyte leakage. DoSPR1-2-GFP preferentially localized to an oryzalin-sensitive cortical microtubule network and colocalized with MBD-mCherry, but not with an actin marker, in Nicotiana benthamiana pavement cells. In representative images, cells co-expressing DoSPR1-2 retained more continuous cortical microtubule arrays during water-deficit treatments. Our findings reveal a close association between DoSPR1-2 abundance, drought-related oxidative responses, and cortical microtubule organization in D. odorifera . These results support DoSPR1-2 as a candidate component involved in coordinating microtubule remodeling during drought stress and suggest that changes in its abundance may contribute to adaptive cytoskeletal reorganization. Together, this study provides new insights into the potential role of DoSPR1-2 in linking drought-responsive cellular processes with microtubule dynamics in D. odorifera .