Single-cell genetic models to evaluate orphan gene function: The case of QQS regulating carbon and nitrogen allocation.

We demonstrate two synthetic single-cell systems that can be used to better understand how the acquisition of an orphan gene can affect complex phenotypes. The Arabidopsis orphan gene, () has been identified as a regulator of carbon (C) and nitrogen (N) partitioning across multiple plant species. modulates this important biotechnological trait by replacing NF-YB (Nuclear Factor Y, subunit B) in its interaction with NF-YC. In this study, we expand on these prior findings by developing and strains, to refactor the functional interactions between QQS and NF-Y subunits to affect modulations in C and N allocation. Expression of in modulates C (, starch) and N (, protein) allocation by affecting interactions between NF-YC and NF-YB subunits. Studies in revealed similar functional interactions between QQS and the NF-YC homolog (HAP5), modulating C (, glycogen) and N (, protein) allocation. However, in both the NF-YA (HAP2) and NF-YB (HAP3) homologs appear to have redundant functions to enable QQS and HAP5 to affect C and N allocation. The genetically tractable systems that developed herein exhibit the plasticity to modulate highly complex phenotypes.