A Transportome amiRNA Forward Genetic Screen Identifies the Auxin Transport Activity of ABCB6 and ABCB20 and Exposes Phenotypic Plasticity in Arabidopsis

Yuqin Zhang ¹ Victoria Naser ¹ Moutasem Omary ¹ Odelia Pisanty ¹ Nikolai Wulff ² Laurence Charrier ³ Iris Tal ¹ Felix Hauser ⁴ Pengchao Hao ³ Hillel Fromm ¹ Julian Schroeder ⁴ Markus Geisler ³ Hussam Hassan Nour-Eldin ² Eilon Shani ¹

¹School of Plant Sciences and Food Security, Tel Aviv University, Israel
²Department of Plant and Environmental Sciences, Faculty of Science, University of Copenhagen, Denmark
³Department of Biology, University of Fribourg, Switzerland
⁴Division of Biological Sciences, Cell and Developmental Biology Section, University of California, San Diego, USA

Transport of signaling molecules is of major importance for regulating plant growth, development, and response to the environment. A prime example is the spatial distribution of auxin, which is regulated via transporters to govern developmental patterning. A critical limitation in our ability to identify novel transporters by forward genetic screens is their functional redundancy within the large plant transporter gene families. Here, we overcome part of this functional redundancy via a transportome, multi-targeted forward-genetic screen using artificial microRNAs (amiRNAs). We generated a library of 3000 T₂ amiRNA lines expressing 1777 amiRNAs targeting subclades in transporter families and identified, genotyped and quantitatively phenotyped, 80 lines showing novel reproducible shoot growth phenotypes. Within this population we discovered and characterized a strong redundant role for the unstudied ABCB6 and ABCB20 genes in auxin transport and signaling. The unique multi-targeted lines generated here could serve as a novel genetic resource that is expected to reveal additional novel transporters.