title: Induction and growth properties of carrot roots with different complements of Agrobacterium rhizogenes T-DNA.
abstract: 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.
authors.affiliation: Dipartimento di Genetica e Biologia Molecolare, Università La Sapienza, Roma, Italy.
authors.forename: I
authors.initials: I
authors.lastname: Capone
authors.forename: L
authors.initials: L
authors.lastname: Spanò
authors.forename: M
authors.initials: M
authors.lastname: Cardarelli
authors.forename: D
authors.initials: D
authors.lastname: Bellincampi
authors.forename: A
authors.initials: A
authors.lastname: Petit
authors.forename: P
authors.initials: P
authors.lastname: Costantino
mesh_terms: D015139:Blotting, Southern; D004247:DNA / Q000235:genetics / Q000302:isolation & purification; D004269:DNA, Bacterial / Q000235:genetics / Q000378:metabolism*; D005798:Genes, Bacterial; D016366:Open Reading Frames; D063245:Plant Development; D010944:Plants / Q000382:microbiology; D015183:Restriction Mapping; D012231:Rhizobium / Q000235:genetics / Q000502:physiology*
chemical_list: D004269:DNA, Bacterial; C036483:T-DNA; D004247:DNA