Bixa orellana (family Bixaceae) is a neotropical fast growing perennial tree of great agro-industrial value because its seeds have a high carotenoid content, mainly bixin. It has been used since pre-colonial times as a culinary colorant and spice, and for healing purposes. It is currently used as a natural pigment in the food, in pharmaceutical, and cosmetic industries, and it is commercially known as annatto. Recently, several studies have addressed the biological and medical properties of this natural pigment, both as potential source of new drugs or because its ingestion as a condiment or diet supplement may protect against several diseases. The most documented properties are anti-oxidative; but its anti-cancer, hypoglucemic, antibiotic and anti-inflammatory properties are also being studied. Bixin’s pathway elucidation and its regulation mechanisms are critical to improve the produce of this important carotenoid. Even though the bixin pathway has been established, the regulation of the genes involved in bixin production remains largely unknown. Our laboratory recently published B. orellana’s transcriptome and we have identified most of its MEP (methyl-D-erythritol 4-phosphate) and carotenoid pathway genes. Annatto is a potential source of new drugs and can be a valuable nutraceutical supplement. However, its nutritional and healing properties require further study.
Bixin is an apocarotenoid obtained from the seed aril of Bixa orellana L., a tropical plant known as achiote in Mexico. This compound is the second most commonly used natural colouring for food and pharmaceutical industries. B. orellana is an outcrossing species that displays high genetic variability. Recently, the colour traits of sexual organs were associated with the biosynthesis and accumulation of bixin in mature seeds. Herein, we describe a new approach for genotype-phenotype association by surveying lycopene beta-cyclase (Bob-LCY1) gene variation in sixteen achiote accessions divided into three groups according to contrasting traits, such as flower colour, fruit colour and bixin production. Using a combination of single-strand conformational polymorphism techniques and the sequencing of polymorphic bands, we identified several single-nucleotide polymorphisms that divided the accessions into three haplotypes. Surprisingly, we observed that these three haplotypes were consistent with the same three groups previously characterized by phenotypic traits. We derived a putative sequence for the Bob-LCY1 gene and surveyed the variations in this sequence. The heterozygosity of Bob-LCY1 alleles resulted in a higher bixin content, likely associated with heterosis for this metabolite. These findings augment the Electronic supplementary material The online version of this article (doi:10.1007/s11032-016-0555-y) contains supplementary material, which is available to authorized users.
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