Rhizobium rhizogenes explained

Rhizobium rhizogenes (formerly Agrobacterium rhizogenes) is a Gram-negative soil bacterium that produces hairy root disease in dicotyledonous plants. R. rhizogenes induces the formation of proliferative multiple-branched adventitious roots at the site of infection, so-called 'hairy roots'.^[1] It also induces galls.

In the rhizosphere, plants may suffer from wounds by soil pathogens or other sources. This leads to the secretion of phenolic compounds like acetosyringone which have chemotactic effects that attract the bacteria. Under such conditions, certain bacterial genes are turned on leading to the transfer of its T-DNA from its root-inducing plasmid (Ri plasmid) into the plant through the wound. After integration and expression, in vitro or under natural conditions, the hairy root phenotype is observed, which typically includes overdevelopment of a root system that is not completely geotropic, and altered (wrinkled) leaf morphology, if leaves are present.^[2] R. rhizogenes also propagates as a seed-borne pathogen.^[3]

Bacterial genes may be retained within the plant,^[4] and sweet potato for instance has retained and actively expresses A. rhizogenes genes which are not present in other members of its genus.^[5]

The hairy roots are grown in vitro in bioreactors to study their soil interaction with other pathogens like fungi and nematodes. This technique has also led to the commercial production of certain metabolic compounds that the plant is known to secrete, especially in regard to the medicinal plants that are difficult to cultivate in sufficient quantities by other means.^[6] The root cultures are also used for genetic engineering.^{[7] [8]}

Notes and References

1. Chilton . Mary-Dell . Tepfer . David A. . Petit . Annik . David . Chantal . Casse-Delbart . Francine . Tempé . Jacques . 1982 . Agrobacterium rhizogenes inserts T-DNA into the genomes of the host plant root cells . Nature . en . 295 . 5848 . 432–434 . 10.1038/295432a0 . 1982Natur.295..432C . 1476-4687.
2. Cardarelli . M. . Mariotti . D. . Pomponi . M. . Spanò . L. . Capone . I. . Costantino . P. . 1987 . Agrobacterium rhizogenes T-DNA genes capable of inducing hairy root phenotype . Molecular and General Genetics MGG . en . 209 . 3 . 475–480 . 10.1007/BF00331152 . 17193709 . 1432-1874.
3. Book: Seed-Borne Diseases of Agricultural Crops: Detection, Diagnosis & Management . . 2020 . 978-981-32-9046-4 . Kumar . Ravindra . en . 10.1007/978-981-32-9046-4 . Gupta . Anuja.
4. Intrieri . Maria Carmela . Buiatti . Marcello . July 2001 . The horizontal transfer of Agrobacterium rhizogenes genes and the evolution of the genus Nicotiana . . 20 . 1 . 100 - 110 . 10.1006/mpev.2001.0927 . 11421651. 2001MolPE..20..100I .
5. Kyndt . Tina . Quispea . Dora . Zhaic . Hong . Jarretd . Robert . Ghislainb . Marc . Liuc . Qingchang . Gheysena . Godelieve . Kreuzeb . Jan F. . The genome of cultivated sweet potato contains Agrobacterium T-DNAs with expressed genes: An example of a naturally transgenic food crop . Proceedings of the National Academy of Sciences of the United States of America . 20 April 2015 . 10.1073/pnas.1419685112 . 112 . 18 . 5844–5849 . 25902487 . 4426443. 2015PNAS..112.5844K . free .
6. Shanks . Jacqueline V. . Morgan . John . April 1999 . Plant 'hairy root' culture . . 10 . 2 . 151–155 . 10.1016/S0958-1669(99)80026-3 . 10209145.
7. Otani . Motoyasu . Mii . Masahiro . Handa . Takashi . Kamada . Hiroshi . Shimada . Takiko . 1993 . Transformation of sweet potato (Ipomoea batatas (L.) Lam.) plants by Agrobacterium rhizogenes . . 94 . 1 . 151 - 159 . 10.1016/0168-9452(93)90016-S . 1993PlnSc..94..151O . 0168-9452.
8. Van de Velde . Willem . Mergeay . Joachim . Holsters . Marcelle . Goormachtig . Sofie . December 2003 . Agrobacterium rhizogenes-mediated transformation of Sesbania rostrata . . 165 . 6 . 1281 - 1288 . 10.1016/S0168-9452(03)00339-X . 2003PlnSc.165.1281V . 0168-9452.