(Reuters) -France's Dassault Systemes lowered its annual operating margin growth forecast on Thursday due to tariff-related market volatility, sending the software company's shares tumbling. Its shares had fallen 9% to the bottom of France's mid-cap SBF 120 index SBF120 and the CAC 40 blue-chip index by 0740 GMT. Dassault, which sells its software to automakers, airplane manufacturers and defence companies, now sees its 2025 operating margin rising by 50-70 basis points, compared to its previous growth expectation of 70-100 bps.