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Summary: 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. [ABSTRACT FROM AUTHOR]

Over the last two decades, the diagnosis and treatment of breast cancer patients have considerably improved. However, brain metastases remain a major clinical challenge and a leading cause of mortality. Thus, a better understanding of the pathways involved in the metastatic cascade is essential. To this end, we have investigated the reciprocal effects of astrocytes and breast cancer cells, employing traditional 2-dimensional cell culture and our unique 3-dimensional multicellular tumoroid models. Our findings revealed that astrocytes enhance the proliferation, migration, and invasion of breast cancer cells, suggesting a supportive role for astrocytes in breast cancer outgrowth to the brain. Elucidating the key players in astrocyte-breast cancer cells crosstalk, we found that CCL2 is highly expressed in breast cancer brain metastases tissue sections from both patients and mice. Our in vitro and in vivo models further confirmed that CCL2 has a functional role in brain metastasis. Given their aggressive nature, we sought additional immune checkpoints for rationale combination therapy. Among the promising candidates were the adhesion molecule P-selectin, which we have recently shown to play a key role in the crosstalk with microglia cells, and the co-inhibitory receptor PD-1, the main target of currently approved immunotherapies. Finally, combining CCL2 inhibition with immunomodulators targeting either PD-1/PD-L1 or P-selectin/P-Selectin Ligand-1 axes in our human 3-dimensional tumoroid models and in vivo presented more favorable outcomes than each monotherapy. Taken together, we propose that CCL2-CCR2/CCR4 is a key pathway promoting breast cancer brain metastases and a promising target for an immunotherapeutic combination approach., (© The Author(s) 2024. Published by Oxford University Press on behalf of the Guarantors of Brain.)