Structure and function of root‐inducing (Ri) plasmids and their relation to tumor‐inducing (Ti) plasmids

Abstract

and function of root-inducing (Ri) plasmids and their relation to tumor-inducing (Ti) plasmids. -Physiol. Plant. 77: 427-435.The abilities of Agrobacterium tumefadens and A. rhizogenes to transform dicotyledons and cause erown gall and hairy root disease are caused by the presence of tumor inducing (Ti) and root inducing (Ri) plasmids. During transformation piasmid T-DNA (transferred DNA) is inserted into the plant genome. The T-region is flanked by 25 bp direct repeats, which are essential for transfer. The T-regions contain oncogenes that are expressed in the plants. Some of these code for enzymes that synthesize auxin or cytokinin. Another type, present in Ri plasmids only, appears to impose a high hormone sensitivity on the infected tissue. The T-DNA also contains genes for enzymes synthesizing opines, which the bacteria catabolize. The T-DNA transfer is initiated by the induction of genes in the virulence (vir) region of the piasmid by phenolic compounds secreted by wounded tissue. The products of the W7--genes and of chromosomal genes mediate transfer of T-DNA to the plant cells. Crown gall disease is caused by production of auxin and cytokinin by the transferred T-DNA. The T-DNA of Ri plasmids codes for at least three genes that each can induce root formation, and that together cause hairy root formation from plant tissue. Current results indicate that the products of these genes induce a potential for increased auxin sensitivity that is expressed when the transformed cells are subjected to a certain level of auxin, After this stage the transformed roots can be grown in culture without exogenous supply of hormones.

Genetic transformation of <i>Ceratotheca triloba</i> for the production of anthraquinones from hairy root cultures

“…For instance similar results were obtained in C. roseus hairy root cultures (Pietrosiuk et al, 2007). Studies show that the biosynthesis of secondary metabolites in hairy root cultures is directed by the effect of the oncogenes (the four rol genes A, B, C and D) (Schmülling et al, 1988;Petersen et al, 1989;Estruch et al, 1991). For example, it has been reported that a correlation exists between the expression of the rolC gene and the production of C. roseus alkaloids (Palazon et al, 1998).…”

Agrobacterium: A disease-causing bacterium

“…Transformation of plant cells results in elevated hormone (auxin and cytokinin) production and sensitivity. Both trigger abnormal proliferation leading to tumorous growth or abnormal rooting (Petersen et al, 1989;Gaudin et al, 1994;Costacurta and Vanderleyden, 1995; see also chapter 15). Tumors and hairy roots produce and secrete specific amino acid and sugar derivatives, called opines.…”

Agrobacterium rhizogenes-Mediated Transformation and Its Biotechnological Applications in Crops

“…T L -DNA of pRi contains the four rol genes, designated as rolA, rolB, rolC and rolD (Schmulling et al 1988;Petersen et al 1989;Gelvin 2003;Bensaddek et al 2008). In Ri plasmid, T L -DNA and T R -DNA are separated from each other by at least 15 kb of non-integrated DNA, which is represented by T-Central DNA (TC-DNA) as seen in Fig.…”

“…Transposon mutagenesis in the T L -DNA has identified at least four genes ( rolA, rolB, rolC and rolD) involved in tumorigenesis as affecting some plants Estramareix et al 1986;Slightom et al 1986;Meyer et al 2000;Christensen et al 2008). All rol genes have been shown to carry out formation of hairy root phenotype Cardarelli 1987a;Jouanin 1987a;Vilaine et al 1987a;Schmulling et al 1988; 1 Agrobacterium rhizogenes-Mediated Transformation … Petersen et al 1989;Lee et al 2001;Bensaddek et al 2008). It has been reported that the T L -DNA of the agropine-type Ri plasmid consists of at least 18 open reading frames (ORF).…”