The Biosynthesis of Non-Endogenous Apocarotenoids in Transgenic Nicotiana glauca

Abstract

Crocins are high-value compounds with industrial and food applications. Saffron is currently the main source of these soluble pigments, but its high market price hinders its use by sectors, such as pharmaceutics. Enzymes involved in the production of these compounds have been identified in saffron, Buddleja, and gardenia. In this study, the enzyme from Buddleja, BdCCD4.1, was constitutively expressed in Nicotiana glauca, a tobacco species with carotenoid-pigmented petals. The transgenic lines produced significant levels of crocins in their leaves and petals. However, the accumulation of crocins was, in general, higher in the leaves than in the petals, reaching almost 302 µg/g DW. The production of crocins was associated with decreased levels of endogenous carotenoids, mainly β-carotene. The stability of crocins in leaf and petal tissues was evaluated after three years of storage, showing an average reduction of 58.06 ± 2.20% in the petals, and 78.37 ± 5.08% in the leaves. This study illustrates the use of BdCCD4.1 as an effective tool for crocin production in N. glauca and how the tissue has an important impact on the stability of produced high-value metabolites during storage.

This work was supported by grants BIO2016-77000-R from the Spanish Ministerio de Ciencia; Innovación y Universidades and SBPLY/17/180501/000234 from the Junta de Comunidades de Castilla-La Mancha (co-financed European Union FEDER funds); the National Natural Science Foundation of China (31870278); and the Spanish Ministry of Economy and Competitiveness (MINECO), Spain (RTI2018–097613-B-I00; PGC2018–097655-B-I00). C.Z. and L.G.G. are participants of the European COST action CA15136 (EUROCAROTEN) and Programa Estatal de Investigación Científica y Técnica de excelencia, Spain (BIO2015–71703-REDT and BIO2017–90877-REDT).