Differing requirements for flavonoids during the formation of lateral roots, nodules and root knot nematode galls in Medicago truncatula.
* In this study, we tested whether the organogenesis of symbiotic root nodules, lateral roots and root galls induced by parasitic root knot nematodes (Meloidogyne javanica) was regulated by the presence of flavonoids in the roots of Medicago truncatula. Flavonoids accumulate in all three types of root organ, and have been hypothesized previously to be required for secondary root organogenesis because of their potential role as auxin transport regulators. * Using RNA interference to silence the flavonoid biosynthetic pathway in M. truncatula, we generated transformed flavonoid-deficient hairy roots which were used to study flavonoid accumulation, cell division and organogenesis of nodules, lateral roots and root galls. * Flavonoid-deficient roots did not form nodules, as demonstrated previously, but showed altered root growth in response to rhizobia. By contrast, flavonoid-deficient roots showed no difference in the number of lateral roots and root galls. Galls on flavonoid-deficient roots formed normal giant cells, but were shorter, and were characterized by reduced numbers of dividing pericycle cells. * We rejected the hypothesis that flavonoids are required as general regulators of the organogenesis of secondary root organs, but flavonoids appear to be necessary for nodulation. Possible reasons for this difference in the requirement for flavonoids are discussed.
Wasson
Anton P
AP
Australian Research Council Centre of Excellence for Integrative Legume Research, Department of Biochemistry and Molecular Biology, School of Biology, Australian National University, Canberra ACT 0200, Australia.
Ramsay
Kerry
K
School of Biological Sciences and Biotechnology, Murdoch University, South Street, Murdoch, Western Australia 6150, Australia.
Jones
Michael G K
MGK
School of Biological Sciences and Biotechnology, Murdoch University, South Street, Murdoch, Western Australia 6150, Australia.
Mathesius
Ulrike
U
Australian Research Council Centre of Excellence for Integrative Legume Research, Department of Biochemistry and Molecular Biology, School of Biology, Australian National University, Canberra ACT 0200, Australia.
D000217:Acyltransferases / Q000378:metabolism; D000818:Animals; D005419:Flavonoids / Q000378:metabolism*; D046913:Medicago truncatula / Q000254:growth & development* / Q000378:metabolism / Q000502:physiology; D009348:Nematoda; D010935:Plant Diseases / Q000469:parasitology*; D055170:Plant Root Nodulation / Q000502:physiology*; D018517:Plant Roots / Q000254:growth & development*; D010941:Plant Tumors / Q000469:parasitology*; D034622:RNA Interference; D053204:Root Nodules, Plant / Q000254:growth & development*; D016962:Sinorhizobium meliloti
D005419:Flavonoids; D000217:Acyltransferases; C020141:flavanone synthetase