Homology mapping of T-DNA regions on three Agrobacterium rhizogenes Ri plasmids by electron microscope heteroduplex studies

Genetically engineered plants producing opines alter their biological environment

Little is known about the consequences of releasing genetically engineered plants (GEP) into the environment. Using opine-producing GEP, we show that transgenic plants alter their biological environment, more precisely the root-associated bacterial populations. The alterations were both transgene-specific and target population-specific. Therefore, assessment studies on the introduction of a given transgene into a GEP will be valid on the given transgene. Evidence of any transgene-associated biological effect will depend on the determination of the pertinent target populations, the identification of which is a key step of such studies.

rol genes of Agrobacterium rhizogenes cucumopine strain: sequence, effects and pattern of expression

By sequencing the central region of the cucumopine-type T-DNA of Agrobacterium rhizogenes strain 2659, we identified three open reading frames homologous, to different extents, to ORFs 10, 11 and 12 (rolA, B and C) of the agropine-type (1855) T-DNA. Recombinant Agrobacterium strains encompassing the ORFs of 2659 T-DNA--which we refer to as rol alpha, beta and gamma--were utilized to infect carrot discs and to obtain transgenic tobacco plants, in order to compare the morphogenetic capabilities to those of the 1855 rol genes. Moreover, a long segment of the 5' non-coding region of rol alpha and rol beta was fused to the GUS reporter gene and the pattern of expression and the responsiveness to auxin of the constructs was analysed in transgenic tobacco. Differences in the auxin requirement for root induction between the 2659 rol genes and their respective 1855 counterparts were pinpointed. These differences are not due to gene regulation and presumably reflect functional differences in the proteins encoded. Differences were also observed in the pattern of expression of rol beta in roots of transgenic plants, as compared to rolB. In addition, the pattern of expression of rol alpha-GUS construct in roots was found to be analogous to that observed for a construct driven by two of the five regulatory domains of the rolB promoter.

Agrobacterium rhizogenes pRi8196 T-DNA: mapping and DNA sequence of functions involved in mannopine synthesis and hairy root differentiation

This paper presents the map and DNA sequence analysis of pRi8196 transferred DNA (T-DNA) genes encoding root-inducing and mannopine synthesis functions. A canonical 24-base-pair border repeat as well as two "pseudoborders" are present at the functional right T-DNA border. To the left of this border are homologs of the mas1' and mas2' genes of TR pRiA4. Next to these are five open reading frames (ORFs) homologous to ORFs 10-14 of TL of pRiA4. ORFs 10-12 (rolA, rolB, and rolC) are less related to their pRiA4 homologs than are the other large ORFs analyzed here. In contrast to T-DNA genes of pRiA4, pRi8196 T-DNA ORFs 11 and 12 (rolB and rolC) are sufficient to induce hairy roots on carrot disks.

Induction and growth properties of carrot roots with different complements of Agrobacterium rhizogenes T-DNA

Single and multiple infections of carrot discs were carried out with Agrobacterium strains harbouring different segments of pRi1855 TL-DNA cloned in the binary vector Bin 19 and with a strain carrying the TR-DNA from the same Ri plasmid. Roots induced by the various co-inoculations were cultured and their growth patterns were followed. Abundant roots could be induced by TL-DNA rol genes A, B and C as a single insert (rolA + B + C) and by rolB alone provided an extended segment beyond its 5' non-coding region was included in the construction. A depression of rooting capability was caused by the inclusion of rolC together with rolB (rolB + C). In all cases co-inoculation with the Agrobacterium carrying TR-DNA-borne auxin genes was necessary for root induction since none of the rol constructions was in itself capable of eliciting any response; an exceeding majority of these roots were however shown to contain rol genes but no TR-DNA. Rooting was also elicited if rol constructions were co-inoculated with a strain carrying TL-DNA genes 13 and 14 (ORF13 + 14) instead of the TR-DNA strain. These roots were shown to contain both rol genes and ORF13 + 14. Striking differences in growth properties were shown by roots containing different complements of TL-DNA genes. Typical hairy root traits, high growth rate, branching and, most noticeably, absence of geotropism, were shown by roots containing rolB alone, while roots with rolA + B + C were geotropic as normal carrot roots. Hairy root traits were conferred to rolA + B + C roots by the concomitant presence of ORF13 + 14 and by the addition of auxin to the culture medium. A model is presented which attempts to rationalize the growth patterns by assigning interplaying roles to the various TL-DNA genes involved.