Our inspiration for the project comes from the team’s group interest in helping others. Cancer is, unfortunately, a disease that many of us deal with today, either directly or through a family member or friend. The majority of our team members have intentions on being involved in the medical sector, and this project allows us to learn about the process of tumorigenesis in a different model organism. While cancer occurs within a multicellular organism, the tumorigenesis experienced by dicot plants is caused by a foreign bacterium, Agrobacterium tumefaciens. Although this mechanism is different than tumorigenesis mechanisms in humans, it can still teach us about tumorigenesis and cancer development nonetheless.

Description

What is Agro?

Agrobacterium Tumefaciens, or Agro for short, is a pathogenic bacteria commonly found in many types of soil. It is most known for infecting plants, mainly eudicots, with crown gall disease.

How does it do this?

Through Ti-plasmids! Tumor-inducing plasmids are the source of the disease, and are manufactured by virulence genes in Agro’s genome. The main proteins within the pathway are VirA and VirG. VirA can be broken up into Periplasmic, Linker, Kinase, and Receiver regions, or P, L, K, and R for short. Though each region is important, our focus has been on the P and L regions. The mechanism for tumorigenesis uses two primary signaling molecules to promote it: phenols and sugars. Sugars are accepted by the P region, and phenols by the L region. Once induced by these molecules, VirA then phosphorylates VirG to complete the process. Below is a detailed image of the pathway for reference.

Hau-Hsuan Hwang, Manda Yu, Erh-Min Lai "Agrobacterium-Mediated Plant Transformation: Biology and Applications," The Arabidopsis Book, 2017(15), (20 October 2017)

Why should you care?

Agro’s infectious nature is a problem for many farmers and agricultural scientists. Crown gall disease affects many commonly grown crops such as grapes, apples, raspberries, almond trees, and even roses, causing millions of dollars in damage each year. Moreover, the current products available only outcompete the wild type. We want to go a step further. Rather than just outcompete the wild type Agro, we want to provide “immunity” to plants. Yes, plants don’t have immune systems in the way that animals do. However, plants do have a slew of chemical and structural defenses.

How You Might Ask?... With Curdlan!

Taguchi, Yoshinari & Ono, Fumiyasu & Tanaka, Masato. (2013). Preparation of Microcapsules Containing β-Carotene with Thermo Sensitive Curdlan by Utilizing Reverse Dispersion. Pharmaceutics. 5. 609-620. 10.3390/pharmaceutics5040609.

Curdlan is a water-insoluble form of glucose that is produced naturally by plants (and other microorganisms) and utilized as a structural molecule; more curdland present allows for a more rigid and sturdy cell wall, which helps the plant defend itself against disease and damage. Curdlan is also known to be produced by Agro. Thus, if we can find a way to synthesize a strain that produces Curdlan at the site of a plant wound, we will have created a type of plant immunity.

References

Pulawska J. Crown gall of stone fruits and nuts, economic significance and diversity of its causal agents: tumorigenic agrobacterium spp. Journal of Plant Pathology. 2010 Jan 18;92(1):S87–S98.
Kawaguchi A, Inoue K, Tanina K, Nita M. Biological control for grapevine crown gall using nonpathogenic Rhizobium vitis strain ARK-1. Proc Jpn Acad, Ser B, Phys Biol Sci. 2017;93(8):547–60.
Pulawska J. Crown gall of stone fruits and nuts, economic significance and diversity of its causal agents: tumorigenic agrobacterium spp. Journal of Plant Pathology. 2010 Jan 18;92(1):S87–S98.
Kawaguchi A, Inoue K, Tanina K, Nita M. Biological control for grapevine crown gall using nonpathogenic Rhizobium vitis strain ARK-1. Proc Jpn Acad, Ser B, Phys Biol Sci. 2017;93(8):547–60.
McCullen CA, Binns AN. Agrobacterium tumefaciens and Plant Cell Interactions and Activities Required for Interkingdom Macromolecular Transfer. Annu Rev Cell Dev Biol. 2006 Nov;22(1):101–27.
Fang F, Lin Y-H, Pierce BD, Lynn DG. A Rhizobium radiobacter Histidine Kinase Can Employ Both Boolean AND and OR Logic Gates to Initiate Pathogenesis. ChemBioChem. 2015 Oct 12;16(15):2183–90.
McCardell BA, Pootjes CF. Chemical nature of agrocin 84 and its effect on a virulent strain of Agrobacterium tumefaciens. Antimicrob Agents Chemother. 1976 Sep;10(3):498–502.
Kim J-G, Park BK, Kim S-U, Choi D, Nahm BH, Moon JS, et al. Bases of biocontrol: sequence predicts synthesis and mode of action of agrocin 84, the Trojan horse antibiotic that controls crown gall. Proc Natl Acad Sci USA. 2006 Jun 6;103(23):8846–51.
Miller JH. Experiments in molecular genetics. New York: Cold Spring Harbor; 1972.
Lin Y-H, Gao R, Binns AN, Lynn DG. Capturing the VirA/VirG TCS of Agrobacterium tumefaciens. Adv Exp Med Biol. 2008;631:161–77.
Lin Y-H, Pierce BD, Fang F, Wise A, Binns AN, Lynn DG. Role of the VirA histidine autokinase of Agrobacterium tumefaciens in the initial steps of pathogenesis. Front Plant Sci. 2014;5:195.
Wang L, Lacroix B, Guo J, Citovsky V. Transcriptional Activation of Virulence Genes of Rhizobium etli. Journal of Bacteriology. 2017 Mar 15;199(6).
Lacroix B, Citovsky V. A Functional Bacterium-to-Plant DNA Transfer Machinery of Rhizobium etli. PLoS Pathog. 2016 Mar;12(3):e1005502.
Li J, Zhu L, Lu G, Zhan X-B, Lin C-C, Zheng Z-Y. Curdlan β-1,3- glucooligosaccharides induce the defense responses against Phytophthora infestans infection of potato (Solanum tuberosum L. cv. McCain G1) leaf cells. PLoS ONE. 2014;9(5):e97197.
Yu X, Zhang C, Yang L, Zhao L, Lin C, Liu Z, et al. CrdR function in a curdlanproducing Agrobacterium sp. ATCC31749 strain. BMC Microbiol. 2015 Feb 10;15:25.
González-Mula A, Lang J, Grandclément C, Naquin D, Ahmar M, Soulère L, et al. Lifestyle of the biotroph Agrobacterium tumefaciens in the ecological niche constructed on its host plant. New Phytol. 2018 Jul;219(1):350–62.
Schäfer A, Tauch A, Jäger W, Kalinowski J, Thierbach G, Pühler A. Small mobilizable multi-purpose cloning vectors derived from the Escherichia coli plasmids pK18 and pK19: selection of defined deletions in the chromosome of Corynebacterium glutamicum. Gene. 1994 Jul 22;145(1):69–73.

[1] Pulawska J. Crown gall of stone fruits and nuts, economic significance and diversity of its causal agents: tumorigenic agrobacterium spp. Journal of Plant Pathology. 2010 Jan 18;92(1):S87–S98.

[2] Kawaguchi A, Inoue K, Tanina K, Nita M. Biological control for grapevine crown gall using nonpathogenic Rhizobium vitis strain ARK-1. Proc Jpn Acad, Ser B, Phys Biol Sci. 2017;93(8):547–60.

[3] Pulawska J. Crown gall of stone fruits and nuts, economic significance and diversity of its causal agents: tumorigenic agrobacterium spp. Journal of Plant Pathology. 2010 Jan 18;92(1):S87–S98.

[4] Kawaguchi A, Inoue K, Tanina K, Nita M. Biological control for grapevine crown gall using nonpathogenic Rhizobium vitis strain ARK-1. Proc Jpn Acad, Ser B, Phys Biol Sci. 2017;93(8):547–60.

[5] McCullen CA, Binns AN. Agrobacterium tumefaciens and Plant Cell Interactions and Activities Required for Interkingdom Macromolecular Transfer. Annu Rev Cell Dev Biol. 2006 Nov;22(1):101–27.

[6] Fang F, Lin Y-H, Pierce BD, Lynn DG. A Rhizobium radiobacter Histidine Kinase Can Employ Both Boolean AND and OR Logic Gates to Initiate Pathogenesis. ChemBioChem. 2015 Oct 12;16(15):2183–90.

[7] McCardell BA, Pootjes CF. Chemical nature of agrocin 84 and its effect on a virulent strain of Agrobacterium tumefaciens. Antimicrob Agents Chemother. 1976 Sep;10(3):498–502.

[8] Kim J-G, Park BK, Kim S-U, Choi D, Nahm BH, Moon JS, et al. Bases of biocontrol: sequence predicts synthesis and mode of action of agrocin 84, the Trojan horse antibiotic that controls crown gall. Proc Natl Acad Sci USA. 2006 Jun 6;103(23):8846–51.

[9] Miller JH. Experiments in molecular genetics. New York: Cold Spring Harbor; 1972.

[10] Lin Y-H, Gao R, Binns AN, Lynn DG. Capturing the VirA/VirG TCS of Agrobacterium tumefaciens. Adv Exp Med Biol. 2008;631:161–77.

[11] Lin Y-H, Pierce BD, Fang F, Wise A, Binns AN, Lynn DG. Role of the VirA histidine autokinase of Agrobacterium tumefaciens in the initial steps of pathogenesis. Front Plant Sci. 2014;5:195.

[12] Wang L, Lacroix B, Guo J, Citovsky V. Transcriptional Activation of Virulence Genes of Rhizobium etli. Journal of Bacteriology. 2017 Mar 15;199(6).

[13] Lacroix B, Citovsky V. A Functional Bacterium-to-Plant DNA Transfer Machinery of Rhizobium etli. PLoS Pathog. 2016 Mar;12(3):e1005502.

[14] Li J, Zhu L, Lu G, Zhan X-B, Lin C-C, Zheng Z-Y. Curdlan β-1,3- glucooligosaccharides induce the defense responses against Phytophthora infestans infection of potato (Solanum tuberosum L. cv. McCain G1) leaf cells. PLoS ONE. 2014;9(5):e97197.

[15] Yu X, Zhang C, Yang L, Zhao L, Lin C, Liu Z, et al. CrdR function in a curdlanproducing Agrobacterium sp. ATCC31749 strain. BMC Microbiol. 2015 Feb 10;15:25.

[16] González-Mula A, Lang J, Grandclément C, Naquin D, Ahmar M, Soulère L, et al. Lifestyle of the biotroph Agrobacterium tumefaciens in the ecological niche constructed on its host plant. New Phytol. 2018 Jul;219(1):350–62.

[17] Schäfer A, Tauch A, Jäger W, Kalinowski J, Thierbach G, Pühler A. Small mobilizable multi-purpose cloning vectors derived from the Escherichia coli plasmids pK18 and pK19: selection of defined deletions in the chromosome of Corynebacterium glutamicum. Gene. 1994 Jul 22;145(1):69–73.