Betalain Synthesis Research Articles

Betalain Pigmentation in Petal of Portulaca is Preceded by a Dramatic Tyrosine Accumulation

Summary To study the turnover of two betalain precursors in magenta petals of Portulaca sp. Jewel, we measured the concentrations of tyrosine and DOPA at distinct developmental stages during flower maturation. A striking increase in tyrosine at least 200 times that in leaves and stems was observed to precede betalain synthesis and petal colorization. The concentration of tyrosine diminished rapidly and synchronously with pigment appearance. The concentration of DOPA, on the other hand, did not follow the same kinetics of accumulation and metabolism as tyrosine and betalain but remained relatively steady at a moderate concentration. Our data indicate an important role of tyrosine as a betalain precursor.

Clonal variability and light induction of betalain synthesis in red beet cell cultures

When calli from a green habituated cell culture of red beet (Beta vulgaris L.) are transfered from dim-light to high-light intensity, red colored spots appear on the surface. Not all cells express the pigmented phenotype, giving rise to variegated patches. The pattern of patch formation is different from one callus to another, although all calluses stem from the same original clone. This clonal variability is an intrinsic property of the tissue and is not affected by light which is only needed for the induction of pigment synthesis, and therefore acts as a revealing factor.

An analysis of the action of light on betalain synthesis in the seedling of Amaranthus caudatus, var. viridis

Accumulation of betalain (amaranthin) in the seedling of Amaranthus caudatus, var. viridis, is inducible by light. Since the apparent lag-phase of amaranthin accumulation after the onset of light is of the order of 3 h, light induction experiments could be performed up to 3 h after the onset of light without interference with actual synthesis. The intricate induction phenomena can be explained as follows: The inductive light operates through phytochrome and through a blue/UV photoreceptor ('cryptochrome'). A phytochrome-dependent 'High Irradiance Reaction' is of minor importance. However, there is a strong, specific interaction between the light effects mediated through phytochrome and cryptochrome in the sense that the 'extent of the reversible response' - (response obtained with a particular light treatment terminated with a saturating red light pulse) minus (response obtained with the same light treatment when terminated with a saturating 756 nm light pulse) -increases with increasing Pfr level and total fluence rate during the induction period. It is concluded that light induced amaranthin synthesis is, in fact, a convenient biochemical model system of photomorphogenesis in the case when phytochrome and cryptochrome operate simultaneously in mediating photomorphogenesis.

Effect of white and far-red light on betalain formation

Light-induced betalain synthesis has been studied in three species of Amaranthaceae. The results obtained suggest that the response to short-term irradiation with white light is mediated by phytochrome, while the effects of prolonged illumination are controlled by the photosynthetic system. Betalain accumulation stimulated by prolonged far-red irradiation is controlled chiefly by the photosynthetic system, the participation of phytochrome being of minor importance.