Opine

Synthesis opines

nopaline

octopine structure

mannopine

Opines are a group of low-molecular-weight compounds found in plant tissues that are produced by a variety of pathogens, most notably bacteria of the genus Agrobacterium. These compounds are synthesized in plant cells after the transfer of a specific segment of DNA, known as the T-DNA, from the bacterium to the plant. This process is part of a larger mechanism of horizontal gene transfer, which Agrobacterium uses to cause diseases such as crown gall in plants. The production of opines is a unique aspect of the interaction between Agrobacterium and its host plants, serving both as a nutrient source for the bacteria and as a marker of the successful genetic modification of the host plant.

Production and Function

The synthesis of opines in infected plant tissues is the result of the expression of genes introduced into the plant genome by the T-DNA from Agrobacterium. These genes encode enzymes that catalyze the production of opines from precursor substances available in the plant cell. The type of opine produced depends on the strain of Agrobacterium involved in the infection, with different strains inducing the synthesis of different opines, such as nopaline, octopine, and agrocinopine.

Opines serve a dual function in the Agrobacterium-plant interaction. Firstly, they act as a unique source of carbon, nitrogen, and energy for Agrobacterium, which possesses the specific catabolic pathways required to utilize these compounds. This gives Agrobacterium a competitive advantage in the ecological niche of the tumor it induces on the plant. Secondly, the production of opines is an indicator of the successful transfer and expression of T-DNA within the plant, essentially marking the transformed cells.

Ecological and Evolutionary Implications

The opine concept has significant implications for our understanding of ecology and evolution. It exemplifies a sophisticated form of parasitism and symbiosis, where a pathogen not only manipulates its host to create a conducive environment for its own survival but also alters the host's metabolism to produce novel compounds that benefit the pathogen. This interaction suggests a high level of co-evolution between Agrobacterium and its host plants.

Furthermore, the study of opines and Agrobacterium-mediated gene transfer has contributed to the development of genetic engineering techniques. The ability of Agrobacterium to introduce foreign DNA into plant cells has been harnessed in the creation of genetically modified organisms (GMOs), making it a tool of immense importance in biotechnology and agricultural science.

See Also

• Agrobacterium
• Crown gall
• Genetic engineering
• Horizontal gene transfer
• Symbiosis