Effects of Agrobacterium tumefaciens strain types on the Agrobacterium-mediated transformation efficiency of filamentous fungus Mortierella alpina.

Four Agrobacterium tumefaciens strains AGL-1, C58C1, EHA105 and LBA4404 were tested for the effects of strain types on the transformation efficiency in Mortierella alpina. Results showed that AGL-1, C58C1 and EHA105 transformed M. alpina successfully. Among them, A. tumefaciens EHA105 was first proven successful transformation of M. alpina. AGL-1 and EHA105 had the highest transformation efficiency among the four strains, while LBA4404 failed to transform M. alpina. The reason leading to the transformation efficiency difference among the four strains was explored by determining transcription levels of the virulence (vir) gene in the induction medium. Results showed that the expressions of virD1, virD2, virD4 and virE1 genes were obviously induced by acetosyringone in all the strains, and their transcriptional levels as well as virA's of AGL-1, C58C1 and EHA105 were higher than that of LBA4404, suggesting high transcriptional levels of vir genes were important for successful transformation. The study selected A. tumefaciens with high transformation efficiency of M. alpina, and would accelerate the genetic management of M. alpina. SIGNIFICANCE AND IMPACT OF THE STUDY: Oleaginous filamentous fungus Mortierella alpina is a commercial strain for the production of arachidonic acid. Genetic manipulation of M. alpina requires highly efficient transformation method. In this study, we explore the effect of Agrobacterium tumefaciens strain types on the transformation efficiency of M. alpina and select A. tumefaciens with the highest transformation efficiency, which accelerates the genetic manipulation of M. alpina. Besides, high transcriptional levels of virulence genes in A. tumefaciens were proven to play an important role for successful transformation.