Abstract
Blakeslea trispora has great potential uses in industrial production because of the excellent capability of producing a large quantity of carotenoids. However, the mechanisms of light-induced carotenoid biosynthesis even the structural and regulatory genes in pathways remain unclear. In this paper, we reported the first transcriptome study in B. trispora in which we have carried out global survey of expression changes of genes participated in blue light response. We verified that the yield of β-carotene increased 3-fold when transferred from darkness to blue light for 24 h and the enhancement of transcription levels of carRA and carB presented a positive correlation with the increase in carotenoid production. RNA-seq analysis revealed that 1124 genes were upregulated and 740 genes were downregulated respectively after blue light exposure. Annotation through GO, KEGG, Swissprot, and COG databases showed 11119 unigenes compared well with known gene sequences, 5514 unigenes were classified into Gene Ontology, and 4675 unigenes were involved in distinct pathways. Among the blue light-responsive genes, 4 genes (carG1, carG3, carRA and carB) identified to function in carotenoid metabolic pathways were dominantly upregulated. We also discovered that 142 TF genes belonging to 45 different superfamilies showed significant differential expression (p≤ 0.05), 62 of which were obviously repressed by blue light. The detailed profile of transcription data will not only allow us to conduct further functional genomics study in B. trispora, but also enhance our understanding of potential metabolic pathway and regulatory network involved in light-regulated carotenoid synthesis.
Highlights
Carotenoids, widely known as lycopene, astaxanthin and other terpenoid compounds. represent a group of naturally occurring pigments with red, orange or yellow color
In order to study the effect of blue light on carotenoid synthesis of B. trispora, we examined the vegetative growth on solid media under dark condition and blue light irradiation
Little difference could be seen in mycelial growth, the hypha appears white-yellowish color after 24 hours inoculation due to the production of small amounts of β-carotene in the dark, while it becomes deep yellow with the increasing blue light exposure time because of the rapid accumulation of β-carotene triggered by blue light (Fig. 1a)
Summary
Carotenoids, widely known as lycopene, astaxanthin and other terpenoid compounds. represent a group of naturally occurring pigments with red, orange or yellow color. Represent a group of naturally occurring pigments with red, orange or yellow color They have a broad market demand and are used extensively as natural colorants in food for years. The strain has great potential uses in industrial production because of the excellent capability of producing a large quantity of lycopene during sexual reproduction (Lopez-Nieto et al 2004). It has been confirmed in B. trispora that lycopene cyclase that mediates lycopene cyclization and lycopene dehydrogenase that converts phytoene to lycopene encoded respectively by carRA and carB are the crucial enzymes for carotenoid biosynthesis (Breitenbach et al 2012; Rodriguez-Saiz et al 2004; Schmidt et al 2005). The carotenoid synthesis was significant improved by continuous light exposure in Mucor circinelloides and Phycomyces blakesleeanus (Almeida and Cerda-Olmedo 2008; Quiles-Rosillo et al 2005), indicating that there existed obviously difference in light signal reception and transduction
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