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. 2008 Jan;101(2):261-5.
doi: 10.1093/aob/mcm032. Epub 2007 Sep 19.

A role for IAA in the infection of Arabidopsis thaliana by Orobanche aegyptiaca

Nurit Bar-Nun  1 , Tsvi Sachs, Alfred M Mayer
Affiliations

A role for IAA in the infection of Arabidopsis thaliana by Orobanche aegyptiaca

Nurit Bar-Nun et al. Ann Bot. 2008 Jan.

Abstract

Background: Vascular continuity is established between a host plant and the root parasite broomrape. It is generally accepted that the direction of vascular continuity results from polar flow of auxin. Our hypothesis was that chemical disruptions of auxin transport and activity could influence the infection of the host by the parasite.

Methods: A sterile system for the routine infection of Arabidopsis thaliana seedlings in Nunc cell culture plates by germinated seeds of Orobanche aegyptiaca was developed. This method permitted a quantitative assay of the rate of host infection. The three-dimensional structure of the vascular contacts was followed in cleared tissue. IAA (indole acetic acid) or substances that influence its activity and transport were applied locally to the host root.

Results: The orientation of the xylem contacts showed that broomrape grafts itself upon the host by acting hormonally as a root rather than a shoot. Local applications of IAA, PCIB (p-chlorophenoxyisobutyric acid) or NPA (naphthylphthalamic acid) all resulted in drastic reductions of Orobanche infection

Conclusions: Broomrape manipulates the host by acting as a sink for auxin. Disruption of auxin action or auxin flow at the contact site could be a novel basis for controlling infection by Orobanche.

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Figures

F<sc>ig</sc>. 1.
Fig. 1.
Xylem connections between the tubercle of Orobanche and the host root, showing the xylem connection oriented towards the host shoot and the reduced size of the host root past the parasite. A, Part of host root above attachment of the parasite in the direction of the shoot; B, tubercle; C, part of host root below attachment of the parasite, in the direction of the root apex. Note: the vascular strands leading from the tubercle (B) curve upwards to the host root (A) in the direction of the shoot apex. The root below the fusion zone (C) is thinner and no vascular strands join it to the root in the direction of the root apex.
F<sc>ig</sc>. 2.
Fig. 2.
Organization of tubercle tissue, showing callus like structure with cell proliferation and scattered partially organized vessels. The outer border of the tubercle is on the left and the vessels are common in the centre and right side of the figure.
See this image and copyright information in PMC

References

    1. Bar Nun N, Mayer AM. Preconditioning and germination of Orobanche seeds: respiration and protein synthesis. Phytochemistry. 1993;34:39–45.
    1. Batchvarova RB, Slavov SB, Bossolova SN. In vitro culture of Orobanche ramosa. Weed Research. 1999;39:191–197.
    1. Berleth T, Sachs T. Plant morphogenesis: long distance coordination and local patterning. Current Opinion in Plant Biology. 2001;4:57–62. - PubMed
    1. Dörr I. New results on interspecific bridges between parasites and their hosts. In: Moreno T, Cubero JI, editors. Advances in parasitic plant research. 1996. pp. 196–201. Congreos y Jornadas, 36/96, Junta de Andalucia, Consejeria de Agricultura y Pessca.
    1. Dörr I, Kollmann R. Strukturelle Grundlagen des Parasitismus bei Orobanche. III. Die Differenzierung des Xylemanschlusses bei. O. crenata. Protoplasma. 1976;89:233–249.