Understanding the convergent evolution of a complex metabolic trait, the Betalains, through comparative genomics and co-expression networks
Plant Genetics and Genomics
Final Report Abstract
Betalain and anthocyanin pigmentation are mutually exclusive in the Caryophyllales. The mechanism of this exclusion eluded researchers for the past 50 years. It is currently assumed that the betalain biosynthesis evolved four times independently and that the anthocyanin biosynthesis was inactivated in these betalain-pigmented lineages. One of these betalain origins shows two betalain biosynthesis genes in close proximity in the genome. The objective of this project was to investigate the evolution of the betalain biosynthesis with focus on the assembly of a metabolic gene cluster. This objective was partly achieved by confirming an independent assembly of a betalain biosynthesis gene cluster in two independent betalain-pigmented lineages. These two lineages acquired betalain biosynthesis through convergent evolution. The presence of biosynthetic gene clusters in both lineages supports the hypothesis that biosynthetic genes clusters might play a role in the evolution of betalain biosynthesis. However, it remains an open question if the betalain biosynthesis genes are clustered in all independent origins of the betalain biosynthesis and to what extend different species of these two origins show clustering. Co-expression analyses were successfully applied for the identification of potential regulators of the betalain biosynthesis. Anthocyanin-related transcription factors showed a strong co-expression with betalain biosynthesis genes suggesting a co-option of the anthocyanin regulators for the regulation of the betalain biosynthesis. A potential block of the anthocyanin biosynthesis in betalain-pigmented species was identified. This has the potential to explain the absence of anthocyanins from betalain - pigmented species i.e. it could explain the mutual exclusion of both pigments.
Publications
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The report of anthocyanins in the betalain-pigmented genus Hylocereus is not well evidenced and is not a strong basis to refute the mutual exclusion paradigm. BMC Plant Biology, 21(1).
Pucker, Boas; Singh, Hidam Bishworjit; Kumari, Monika; Khan, Mohammad Imtiyaj & Brockington, Samuel F.
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The evidence for anthocyanins in the betalain-pigmented genus Hylocereus is weak. BMC Genomics, 23(1).
Pucker, Boas & Brockington, Samuel F.
