Enlarged map ofAgrobacterium tumefaciens C58 and the location of chromosomal regions which affect tumorigenicity

Abstract

A revised and enlarged genetic map of the Agrobacterium tumefaciens C58 chromosome has been produced with the help of plasmid R68.45. Apart from the location of several auxotrophic markers, the map also shows the position of two independent genes, ctul and ctu2, which, when mutated, block the tumorigenesis of the bacterium. Of these two, only ctul is complemented by the C58 chromosomal vir region cloned by Douglas et al. (1985). The same mutant was complemented by a chromosomal gene or genes located near leu of Rhizobium meliloti and known to affect the nodulation properties of that bacterium. It has also been observed that C58 tryptophan auxotrophs invariably lose tumorigenicity. Prototrophic revertants and mutants supplied with extra tryptophan for about two weeks after infection produce normal tumours. These investigations suggest that for successful tumorigenesis a continuous supply of tryptophan is needed (to be converted into auxin IAA?) at least during the early stages.

Mapping of Agrobacterium tumefaciens chromosomal genes affecting cellulose synthesis and bacterial attachment to host cells

“…They both mapped to the same region as the cel mutations. This region is distant from the suggested locations for the chvAB genes, which also affect bacterial attachment to host cells (11,13). Since many of the cel and att mutations mapped are apparently located very close to each other, the exact order of the mutations in this region as presented here must be regarded as tentative.…”

Intergeneric complementation by Agrobacterium tumefaciens chromosomal genes and its potential use for linkage mapping

“…The chromosomal region displayed in Fig. 1 allows to compare the circular maps established by Hooykaas et al [4] and by Miller et al [6]. The former map reports 3 loci met-43, leu-4 and trp-13 for this chromosomal region.…”

“…Mobilization of the Agrobacterium chromosome can be achieved with the Inc P1 plasmid R68.45 at a reasonably high frequency [4][5][6]20].…”

“…These contradictions clearly show the need for enzymatic determination of the different trp and leu mutations. R prime plasmids, as described in this paper, can be used to establish a detailed comparison between both existing circular linkage maps of A. tumefaciens [4,6] as they allow to test complemenration of the different mutants with the same chromosomal fragment.…”

“…Mutants carrying a Tn5 insertion in either one of these loci are defective in their ability to attach to plant cells. Mapping of Agrobacterium chromosomal markers has essentially been achieved by using the chromosome mobilizing activity of the IncP1 type plasmid R68.45 [4][5][6]. In this paper we present a different mapping strategy, through the isolation and subsequent characterization of R prime plasmids.…”