2/2 @hotvegetables.bsky.social now solved this mystery, showing that this locus is responsible for natural variation in root architecture in response to commensal Pseudomonas — likely due to local adaptation
www.biorxiv.org/content/10.1...

Plants often struggle to obtain sufficient iron from the soil. Plant metabolites, in concert with root microbes, can enhance iron availability. Here, a root fungal endophyte improves Arabidopsis iron nutrition in synergy with plant-derived coumarins.

Thank you!!