Bixin biosynthesis in annatto (Bixa orellana L.) leaves cultured in vitro: influence of irradiance, spectral light quality and the methyltransferase inhibitor 5-azacytidine

• Ano de defesa: 2019
• Autor(a) principal: Faria, Daniele Vidal
• Tipo de documento: Tese
• Tipo de acesso: Acesso aberto
• Idioma: eng
• Instituição de defesa: Universidade Federal de Viçosa; Botânica
• Palavras-chave em Português: Bixa orellana; Bixina - Análise; 5-azacitidina; Irradiação; Luz; Fisiologia Vegetal
• Link de acesso: https://locus.ufv.br//handle/123456789/29315

Annatto (Bixa orellana L.) is an important functional food and the unique exploited source for the production of natural dye bixin and norbixin, widely used in the food, pharmaceutical, cosmetic textile and othes industries. The bixin are produced in all plant tissues and accumulated in secretory structures, enabling use the in vitro tissue culture for micropropagation and study of the bixin pathway in the other tissues. However, its biosynthesis pathway and regulation are still not well understood. The genes carotene cleavage dioxygenase (CCD4), aldehyde dehydrogenase (ALDH) and SABATH family methyltransferase (SABATH) are involved with the bixin biosynthesis, since they are overexpressed in immature seeds and are related to carotenoids and apocarotenoids accumulation. Treatments with demethylating agents, such as 5-azacytidine (5-AZA) were previously related to an increased production of secondary compounds and used to study secondary metabolism pathways in plants. The light are characterized by irradiance, wavelength or quality and direction, all these factor can influence in development, growth and in several physiological processes such as in the production of plant secondary metabolites in vitro. Aiming to study the influence of DNA demethylating compound on the bixin pathway in B. orellana cv. Piave Vermelha leaves, we evaluated for the first time the effect of 5-AZA in the global methylation, the expression of some bixin pathway candidate genes, as well as the bixin content, chlorophylls and total carotenoids in the leaves of B. orellana in vitro grown plants. The temporary exposure of shoots apexes cultured in vitro to the demethylating compound 5-AZA did not affect the genome global methylation, chlorophylls and total carotenoid content in leaves of B. orellana. However, plants submitted to 5-AZA showed downregulation of SABBATH family genes and increased the bixin content in the leaves, suggesting that this methyltransferase inhibitor can direct regulate the biosynthesis pathway and the production of bixin in B. orellana. In addition, aiming to study the influence of different light conditions in the in vitro culture of B. orellana, we analysed for the first time the effect of irradiance and light quality on shoot apexes cultured in vitro. The number of leaves per plant, stomatal density, leaf area and leaf expansion, chlorophylls, total carotenoids, malondialdehyde (MDA) and bixin content were analysed in the leaves of B. orellana ‘Piave Vermelha’ and ‘UESB74’ cultured in vitro. The fist produces 1.6-fold more bixin in leaves than the latter and visibly higher bixin content in the seeds. The stomata cells in the leaves of both cultivars were in paracytic arrangement, whit peltate trichomes predominant along the adaxial and abaxial surfaces of the leaf. For in vitro culture of ‘Piave Vermelha’ the blue/red LED light was the best, on the other hand for ‘UESB74’, the culture in fluorescent light is indicared, if the use fluorescent light is chosen for both varieties, are indicated the irradiance of 50 μmol m -2 s -1 is the must recommented. This work opens perspectives about the regulation of the pathway and the heterogeneity of the biosynthesis pathway of bixin.