Do Plants Get Cancer?

Abstract:

Have you ever thought about plants getting tumors and having cancer? You might have been surprised after you heard this. However, it is a fact. If humans or other animals get cancer, then plants also can be infected by it. Scientists have efficiently researched the phenomenon and found this crucial fate that actually affects the growth and development of plants. Probably, you are thinking, how does it occur? Well, let's see how it happens.

Introduction:

Figure: Crown Gall Disease in plants

The tumor which is observed in the plants is known as Crown Gall Disease. In 1679, Malpighi first observed the galls in plants. Later, in 1897, Fridiano Cavara in Napoli, Italy discovered the facts behind the crown gall disease of plants by isolating the causing microorganism, Agrobacterium tumefaciens. Two scientists E.F. Smith and C.O Towsend, visited Napoli, Italy, to find crown gall disease in 1907. Later on, they published their paper on this cancerous disease in 1952. After that, other microbiologists and botanists researched the phenomenon and wrote different conclusions. One of the scientists, George Hedgcock, enlightened the cause and effects of crown gall disease in the grapevines and woody shrubs and published his article in 1910. There he elucidated his work on isolating the bacterium from the herbaceous plants.

Mechanism of Crown Gall Disease in Plants:

We have already come to know the existence of the tumor of plants in the grapevines, woody shrubs, and herbaceous plants. Most likely, you are thinking about where the crown gall disease exactly occurs. The straightforward answer is - in the roots where the branches of the plants originate. The gram-negative bacteria Agrobacterium tumefaciens live in the soil. When the plants get wounds or cuts in the roots above the ground, they immediately infect the wounds. Then, opines-like tumors are formed, which are low molecular weight secondary amine derivatives. Opines are formed by the two amino acids, nopaline, and octopine. Surprisingly, tumor formation of the plants is caused by the three molecules: Opines, Auxin, and Cytokinin. Auxin and Cytokinin are the phytohormones of the plants' growth and development. Still, excessive amounts of these phytohormones enhance the formation of the tumor or crown gall disease in the plants. The plants' tumor formation occurs by the gene insertion of Agrobacterium into the plants' wounds. Agrobacterium's Ti-plasmid (Tumor-inducing plasmid) transfers the t-RNA into the plants, done in protein synthesis. Right after the insertion of the gene in the plant DNA, Agrobacterium leaves the plants, and again it sets up in the soil. Then, it utilizes the proteins from the opines. It indicates that Agrobacterium is not present in the infected tumor after it infects the plants.

Figure: Life cycle of Agrobacterium tumefaciens

The wounds of the plants secrete acetosyringone which is a phenolic compound. This phenolic compound gives a signal to the Agrobacterium tumefaciens to infect the plant. The Vir-A gene, which is present in Agrobactrium's Ti-plasmid, recognizes the sign of acetosyringone. The chvE (chromosomal gene coated protein) protein recognizes the sugars, and along with the Vir-A gene, it activates the other vir (virulence region) genes. Vir-G, which is present in the cytoplasm, is a transcription factor. It enhances the transcription of vir (virulence region) operons. After that, Vir-C cleaves the target sequence of the host plant's DNA and attaches it to it. This is how the tumor is formed in the plants' roots. Since crown gall disease is very contagious, it affects the movement of plants' nutrients and growth.

Conclusion:

In a nutshell, crown gall disease is a curse for herbaceous plants. However, the crown all disease is not as lethal as animal cancer. In addition, Agrobacterium tumefaciens can be used as a tool for the gene modification of plants. So, the Ti-plasmid of this bacterium is used to modify the plants' gene, which is very beneficial in Biotechnology. It is crystal clear that the bacteria that causes the tumor is industrially helpful to scientists. Isn't it amazing?