Plant compounds that are perceived by humans to have color are generally referred to as 'pigments'. Their varied structures and colors have long fascinated chemists and biologists, who have examined their chemical and physical properties, their mode of synthesis, and their physiological and ecological roles. Plant pigments also have a long history of use by humans. The major classes of plant pigments, with the exception of the chlorophylls, are reviewed here. Anthocyanins, a class of flavonoids derived ultimately from phenylalanine, are water-soluble, synthesized in the cytosol, and localized in vacuoles. They provide a wide range of colors ranging from orange/red to violet/blue. In addition to various modifications to their structures, their specific color also depends on co-pigments, metal ions and pH. They are widely distributed in the plant kingdom. The lipid-soluble, yellow-to-red carotenoids, a subclass of terpenoids, are also distributed ubiquitously in plants. They are synthesized in chloroplasts and are essential to the integrity of the photosynthetic apparatus. Betalains, also conferring yellow-to-red colors, are nitrogen-containing water-soluble compounds derived from tyrosine that are found only in a limited number of plant lineages. In contrast to anthocyanins and carotenoids, the biosynthetic pathway of betalains is only partially understood. All three classes of pigments act as visible signals to attract insects, birds and animals for pollination and seed dispersal. They also protect plants from damage caused by UV and visible light.

https://onlinelibrary.wiley.com/doi/epdf/10.1111/j.1365-313X.2008.03447.x

Biosynthesis of plant pigments: anthocyanins, betalains and carotenoids

https://pubag.nal.usda.gov/download/25475/PDF

Salinity–mineral nutrient relations in horticultural crops

1-Methylcyclopropene: a review

Anthocyanins and betalains play important roles both in plant physiology, visual attraction for pollinators and seed dispersers, but also in food mainly defining its aesthetic value. Since anthocyanin and betalain structures allow to predict only part of their appearance, additional chemical and anatomical functions are required to modulate the appearance of plants and coloured food. Physiological effects that the same pigments exert in plants are supposedly similar to those which they show in humans following ingestion of coloured food. Therefore, anthocyanins and betalains both in fresh and also processed fruit and vegetables serve two functions: They improve the overall appearance, but also contribute to consumers' health and well-being.

Functional properties of anthocyanins and betalains in plants, food, and in human nutrition

The development and maturation of fruits has received considerable scientific scrutiny because of both the uniqueness of such processes to the biology of plants and the importance of fruit as a significant component of the human diet. Molecular and genetic analysis of fruit development, and especially ripening of fleshy fruits, has resulted in significant gains in knowledge over recent years. Great strides have been made in the areas of ethylene biosynthesis and response, cell wall metabolism, and environmental factors, such as light, that impact ripening. Discoveries made in Arabidopsis in terms of general mechanisms for signal transduction, in addition to specific mechanisms of carpel development, have assisted discovery in more traditional models such as tomato. This review attempts to coalesce recent findings in the areas of fruit development and ripening.

/pdf/molecular-biology-of-fruit-maturation-and-ripening-149p5o0zzm.pdf

Molecular biology of fruit maturation and ripening.

We present a simple protocol for DNA isolation from climbing cacti, genera Hylocereus and Selenicereus. The abundant polysaccharides present in Hylocereus and Selenicereus species interfere with DNA isolation, and DNA extracts, rich in polysaccharides, are poor templates for amplification using polymerase chain reaction (PCR). We used roots as the source tissue due to the lower viscosity of the extracts relative to that of other tissues. The extraction and isolation procedure we devised consists of the following steps: (1) three washes of ground tissue with the extraction buffer to remove the polysaccharides; (2) extraction with high-salt (4 M NaCl) cetyltrimethylammonium bromide (CTAB) buffer to remove the remaining polysaccharides; (3) removal of RNA by RNase; (4) phenol:chloroform extraction to remove proteins; (5) chloroform extraction to remove remaining phenols. The yields ranged from 10 to 20 μg DNA/g fresh roots. DNA samples prepared by our method were consistently amplifiable in the RAPD reaction and gave reproducible profiles.

Modified CTAB Procedure for DNA Isolation from Epiphytic Cacti of the Genera Hylocereus and Selenicereus (Cactaceae)

Responses of climacteric and suppressed-climacteric plums to treatment with propylene and 1-methylcyclopropene

Cacti as Crops

Determination of profiles and total contents of betacyanins in cactus fruits of Hylocereus species using chromatographic and spectrophotometric method is described. The investigated species were H. polyrhizus, H. purpusii, H. costaricensis, H. sp. 487 (all red-flesh species and hybrids made among them), and the white- or red-flesh species H. undatus. Hybrids included hybrid 1 (H. undatus white-flesh clone and H. sp. 487), hybrid 35 (H. sp. 487 and H. polyrhizus), and the reciprocal hybrid hybrid 95 (H. polyrhizus and H. sp. 487). Fruits of H. polyrhizus exhibited the highest relative concentration (expressed as percentage of the total HPLC peak area) of hylocerenin, a recently discovered pigment, and a high relative concentration of phyllocactin. Hylocerenin and isohylocerenin, present in fruits at relative concentrations of 11.7 and 5.8%, respectively, are probably responsible for the fluorescent color of the fruit pulp. H. costaricensis fruits have a much higher content of phyllocactin (63.9%), which is almost 4 times higher than the betanin content. These differences in pigment concentrations might explain the differences in red hues of the flesh of these fruits.

Yosef Mizrahi

Papers

Modified CTAB Procedure for DNA Isolation from Epiphytic Cacti of the Genera Hylocereus and Selenicereus (Cactaceae)

Responses of climacteric and suppressed-climacteric plums to treatment with propylene and 1-methylcyclopropene

Cacti as Crops

Fruit flesh betacyanin pigments in hylocereus cacti.

Betacyanins from vine cactus Hylocereus polyrhizus.