Previously, we have reported a T-DNA tagged mutant (TAG_009) of Arabidopsis thaliana exhibiting a significant sensitivity to biotic stresses. We have also cloned and analyzed the tagged gene At5g46050. Based on bioinformatic and molecular characterization, we proposed that At5g46050 is involved in the transport of peptides participating in plant defense against biotic stresses. To provide further evidence for supporting our proposal, this time we exposed this mutant to Fusarium culmorum, a potential fungal pathogen. Besides TAG_009 line, in our investigations we included two SALK insertion mutants (SALK_003119 and SALK_145209), two wild-type ecotypes (WT_C24 and WT_Col-0) and an additional T-DNA tagged mutant (TAG_197-6) of A. thaliana. We have found that the highest degree of leaf damage was exhibited by TAG_009 line (damage score 4.37), whereas the lowest was observed in WT_Col-0 ecotype (damage score 3.43). The highest rate of mortality after eight weeks of inoculation with F. culmorum was also observed in TAG_009 line (85.24%), while the lowest was in WT_Col-0 line (37.22%). We have also found that plants of SALK_145209 line, despite being infected with Fusarium, produced the highest number of leaves (average 14.17 leaves per plant), whereas the lowest number of leaves was produced by plants of TAG_197-6 line ( average 9.5 leaves per plant). Statistical analyses showed that the differences between the T-DNA tagged line TAG_009 and WT_Col-0 were significant, whereas in comparison with wild-type control plants WT_C24, they were insignificant. Based on these results, we can conclude that the gene we have tagged by using T-DNA-mediated in vivo gene fusion is indeed involved in the plant defense against Fusarium infection.