Fig. 9

Schematic diagrams of possible roles played by ERG28 gene and the two DNA repair genes in AMT. a During co-cultivation with the Agrobacterium cells, cell division of the wild type yeast cells is suppressed by the presence of the donor cells, while, the erg28Δ cells continue to grow in the same condition. ERG28 gene product has a role in sensing congestion environment, and then suppresses cell division. Although wild-type cells can keep high AMT ability during co-cultivation, erg28Δ cells continue cell division and hence reduce AMT activity. When higher number of cells are loaded to co-cultivation, even wild type cells reduce AMT activity and exhibit the erg28Δ mutant level of low efficiency. b Chromosomal T-DNA contains the YAC encoding autonomous replication and segregation factors and telomere sequences. Upon the entry into nucleus, the single-stranded T-DNA (ssT-DNA) is converted into double-stranded T-DNA (dsT-DNA) and starts to replicate as a linear replicon. The SRS2 and RAD52 genes act soon after T-DNA entry for modification of the T-DNA to stably maintain them as linear replicons and to circularize certain T-DNA simultaneously. The linear replicon (chromosomal T-DNA) is unstable in the srs2Δ and rad52Δ mutants, hence needs circularization of the replicon, although the two mutants have lower circularization abilities and result in the formation of few AMT colonies