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A Comparison of Anthocyanin Biosynthesis in Four Plant Species

Introduction

Anthocyanins are phenolic compounds that belong to the group of flavonoids. The anthocyanins (from Greek anthos, flower, and kyanos, dark blue) are colored pigments that are commonly found in angiosperms. They have also been reported in mosses and some fungi. Anthocyanins are located in the vacuoles of epidermal cells. Their distribution in the plant varies according to the plant genotype, age and various abiotic and biotic factors. They have been found in most plant parts, flowers, leaves, fruits, stems, roots and storage organs.

The diversity of anthocyanins is vast. These aglycones can undergo a variety of biochemical reactions, such as hydroxylation, methylation, glucosylation, acylation, prenylation or sulphanation; resulting in their structural diversity (Dey and Harborne, 1993). The type of compound attached to the basic structure greatly influences the color of the anthocyanins. For example, the attachment of methyl groups can result in reddish color and the presence of flavones or flavonols can cause a more blueish color (Salisbury and Ross, 1992). The color is also highly affected by pH.

Anthocyanins have long been known as attractants for pollinators of flowers and for fruit dispersers. They are thought to give protection against UV and intense white light. They also may be involved in defense against pathogen invasion.

The structure, function and interaction of genes involved in anthocyanin biosynthesis has prompted intense study by geneticists, biochemists and plant breeders. We focus on anthocyanin biosynthesis and regulation. using four plant species as case studies, two of which are historically model plants for molecular anthocyanin studies: Zea mays (maize) and Petunia hybrida. The other two species are relative newcomers to the molecular study of anthocyanin production: Vitis vinifera (grape) and Arabidospsis thaliana. Anthocyanin distribution and production has been studied extensively in Vitis vinifera (grape) due to its economic importance in the wine industry. However, biochemical and molecular studies of anthocyanin production involving Vitis species are rare. Arabidopsis thaliana has only recently become the target of anthocyanin studies. These plants represent good models for the study of anthocyanin biosynthesis and regulation due to the different patterns of accumulation of the pigments. Anthocyanins are more abundant in the flowers in petunia the seeds in maize, and the fruit in grapes than they are in the other parts of the plants. Anthocyanins are found in all organs of Arabidopsis.

(By: Rejane Guimaraes)

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REFERENCES

Dey, PM and Harborne, JB. 1993. Methods in Plant Biochemistry. In: Flavonoid Enzymology. Pgs. 99-131. Academic Press. (editor: Lea, PJ)

Salisbury, R and Ross, C. 1992. In: Plant Physiology. 4^th edition. (editor: Kauser, RM). Wadsworth Publishing Company, Belmont, CA.