Ferritins, the multimeric iron storage proteins, are the main regulators of the cellular level of uncomplexed iron. Ferritins are encoded by small gene families and expressed differentially under various developmental conditions depending on iron availability, effect of hormones or oxygen radical generating agents. In the present work the primary structure of the ferritin2 gene from resistant and susceptible biotypes of horseweed Conyza canadensis was determined. This gene was found to exhibit great similarity and possess all the structural characteristics of known plant ferritin2 genes. The C. canadensis ferritin2 genes had identical primary structure in the two biotypes and were upregulated by paraquat (Pq) in both susceptible and resistant plants. The enhanced expression level was probably connected with defence reactions in the plants after Pq treatment.