Regulation of Pigment-Related Genes During Flower and Fruit Development of Bixa orellana

Abstract

Annatto (Bixa orellana) is the sole source of the commercially important pigment bixin. The broad diversity of annatto phenotypes and the wide variation in pigment contents have restricted its use. Therefore, genetic improvement focusing on this variation is important in order to achieve optimal exploitation of annatto. To characterize and understand some of the genetic basis governing carotenoid production, two annatto cultivars with either pink or white flowers were selected on the basis of their contrasting pigment levels. Several complementary DNA (cDNA)-probes corresponding to genes involved in carotenoid biosynthesis (dxs, psy, pds, β-lcy, and ε-lcy) were cloned and analyzed by reverse transcriptase-polymerase chain reaction (RT-PCR) in different tissues of these two annatto cultivars during flower and fruit development. In general, expression of most selected genes could be associated with pigment overaccumulation in these cultivars. The pink cultivar exhibited higher carotenoid contents and higher pigment-related gene expression, and the two variants analyzed showed notable differences in gene expression in the highest pigment producing tissues.

Functional polymorphism in lycopene beta-cyclase gene as a molecular marker to predict bixin production in Bixa orellana L. (achiote)

“…Thus, the identification of molecular markers is of applied importance. Previous studies using two achiote variants with contrasting phenotypes suggested an association between Bob-LCY1 gene expression and the bixin content in mature seeds and flower and fruit colour (Rivera-Madrid et al 2006;Valdez-Ojeda et al 2010;Rodríguez-Á vila et al 2011). We therefore investigated allelic variation in the Bob-LCY1 gene using the SSCP method (Orita et al 1989), a technique that detects DNA variation in small amplicons, to identify SNPs associated with phenotypic traits.…”

“…Sixteen B. orellana individuals from the germplasm bank located in CRUPY (Centro Regional Universitario de la Peninsula de Yucatan, Mexico) were chosen for this study based on the associations observed previously between the plant colour traits and bixin accumulation in mature seeds (Rivera-Madrid et al 2006;Valdez-Ojeda et al 2010;Rodríguez-Á vila et al 2011). These plants were originally collected from Yaxcaba, Cooperativa and Chicxulub Pueblo (the achiote plantation of the 'La Extra' Company), from the cultivation region of Yucatan State located at latitude 20°13 0 to 20°29 0 and longitude 88°55 0 to 89°54 0 .…”

“…Thus, in two accessions of achiote differing in pigment content, Bob-LCY1 mRNA expression was correlated with carotene accumulation (Rodríguez-Á vila et al 2011). Additionally, in some plants, such as capsicum, watermelon, papaya and maize, DNA sequence polymorphisms in cyclase genes are associated with the pigment phenotype (Bang et al 2007;Ha et al 2007;Harjes et al 2008;Devitt et al 2010).…”

“…Given the economic potential of bixin, the early identification of promising plants in breeding programmes would be advantageous. Previous studies aimed at genetic improvement have identified the phenotypic traits of achiote plants associated with differential pigment accumulation in mature seeds, such as the colour of the flower and fruit and pod dehiscence (Rivera-Madrid et al 2006;Valdez-Ojeda et al 2010;Rodríguez-Á vila et al 2011). However, genetic selection based on sexual traits is difficult because the first flowering occurs in the third or fourth year after seed germination, followed by the annual flowering.…”

“…The analysis of B. orellana gene transcripts encoding carotenoid biosynthesis enzymes revealed that PDS, b-LCY and e-LCY genes are highly regulated at different stages of plant development and in plant accessions with different flower and fruit colours (Rodríguez-Á vila et al 2011). Thus, in two accessions of achiote differing in pigment content, Bob-LCY1 mRNA expression was correlated with carotene accumulation (Rodríguez-Á vila et al 2011).…”