"Crazy roots" pathogen, Agrobacterium bv1 with Ri plasmid, change plant roots geotropism. Any idea how the pathogen makes it?
"Gravity sensing takes place in the columella cells of the root cap, where sedimentation of starch-filled plastids (amyloplasts) triggers a pathway that results in a relocalization to the lower side of the cell of PIN proteins, which facilitate efflux of the plant hormone auxin efflux. Consequently, auxin accumulates in the lower half of the root, triggering bending of the root tip at the elongation zone. " Citation from Su, Shih-Heng, et al. "Molecular mechanisms of root gravitropism." Current Biology 27.17 (2017): R964-R972.
Thus, independent production of auxin by Ri-transformed cells can change the direction of growth?
Hello Alex, your agrobacterium strain has ri plasmid and it also posessive rol genes and aux genes. The rol genes are responsible for this hairy root syndrome. These roots are negatively geotropic and it multiples laterally. You can culture these roots in liquid media it has high biosynthetic ability and metabolites.
Aaqib Javid Monisha Mitra Yuan-Yeu Yau Thank you everybody !
The "crazy roots" pathogen was obtained from disease outbreak in Russia from 2014 till the present time. Original description of pathogen causing disease in UK since 1993 was made by Weller, S. A., et al. "Rhizogenic Agrobacterium biovar 1 and cucumber root mat in the UK." Plant pathology 49.1 (2000): 43-50., and first isolates of Agr. bv. 1 were found in UK at 1974,
including NCPPB 2659, used for plant transformantion in many experiments (just for example: R. H. Berg, et al, Induction of Pseudoactinorhizae by the Plant Pathogen Agrobacterium rhizogenes , Plant Physiology, 1992, 98 (2):777–779.
I believe that pathogen could escape from experimental plants in early 1990-s, or it was applied for purpose like at Christensen, B., and R. Müller. "The use of Agrobacterium rhizogenes and its rol-genes for quality improvement in ornamentals." European Journal of Horticultural Science 74.6 (2009): 275. The infected potato plant already show more rapid growth, it is interesting to see effect of tubers yield.
Recently, Agr.bv1 was found in gardens and fields on carrot, physalis and apple young plants, probably due to its large-scale presence in modern greenhouses on hydroponic vegetables, and superior resistance to soil antagonists and biological disease control agents..
Hello Alex if you plan to carry out any research activity with this pathogen. I can suggest you can isolate this pathogen and create a pure culture of it. Normally pure cultures are streaking it and making single colonies. Meanwhile the roots which you have observed you can go for these tests
1. Go for mass spectrometry
2. If you don't have such facilities for initial investigation try some qualitative tests.
3. You can assess the flavonoids or phenols using quantitative protocols by UV-vis mass spectrometry
4. You can check if any rol genes are present by going for a pcr
5. You can isolate the plasmid dna from the bacteria and also go for rol genes
Monisha Mitra Thank you for suggestion. We have isolated the pathogen several years ago and confirmed identity of the isolates by PCR, virulence and MLST. I hope to publish report about their diversity this year.
Ignatov, A. N., et al. "First report of rhizogenic strains of Agrobacterium radiobacter biovar 1 causing root mat of cucumber and tomato in Russia." Plant Disease 100.7 (2016): 1493-1493.
PS: Strains with Ri plasmid are very different from Ti even in virulence test. Look at carrot reaction:
Yes, Virulence depends on many factors. But I guess this strain is much more efficent than strains I have come accross. Have you isolated pure culture ?
Aaqib Javid These carrot disks are infected by identified strains. I use for Agrobacterium isolation a very simple medium (not published yet) with good selectivity. Fluorescent Pseudomonas sp. is the only contaminating bacteria type.
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