Isoform-resolved genome annotation enables mapping of tissue-specific betalain regulation in amaranth
Authors
Tom S. Winkler∗ , Susanne K. Vollmer∗† , Nadine Dyballa-Rukes‡ , Sabine Metzger‡ and Markus G Stetter∗,1
∗ Institute for Plant Sciences and Cluster of Excellence on Plant Sciences (CEPLAS), University of Cologne, Cologne, Germany, † Heinrich Heine University,
Duesseldorf, Germany, ‡ MS platform, Institute for Plant Sciences and Cluster of Excellence on Plant Sciences (CEPLAS), University of Cologne, Cologne,
Germany
Study description
- Betalains are coloring pigments produced in some families of the order Caryophyllales, where they replace anthocyanins as coloring pigments. While the betalain pathway itself is well studied, the tissue-specific regulation of the pathway remains mostly unknown.
- We enhance the high-quality Amaranthus hypochondriacus reference genome and produce a substantially more complete genome annotation, incorporating isoform details. We annotate betalain and anthocyanin pathway genes along with their regulators in amaranth and map the genetic control and tissue-specific regulation of the betalain pathway.
- Our improved genome annotation allowed us to identify causal mutations that lead to a knock-out of red betacyanins in natural accessions of amaranth. We reveal the tissue-specific regulation of flower color via a previously uncharacterized MYB transcription factor, AhMYB2. Downregulation of AhMYB2 in the flower leads to reduced expression of key betalain enzyme genes and loss of red flower color.
- Our improved amaranth reference genome represents the most complete genome of amaranth to date and is a valuable resource for betalain and amaranth research. High similarity of the flower betalain regulator AhMYB2 to anthocyanin regulators and a partially conserved interaction motif support the co-option of anthocyanin regulators for the betalain pathway as a possible reason for the mutual exclusiveness of the two pigments.
Citation
Winkler, T. S., Vollmer, S. K., Dyballa‐Rukes, N., Metzger, S., & Stetter, M. G. (2024). Isoform‐resolved genome annotation enables mapping of tissue‐specific betalain regulation in amaranth. New Phytologist.