A seed resource for screening functionally redundant genes and isolation of new mutants impaired in CO2 and ABA responses

The identification of homologous genes with functional overlap in forward genetic screens is severely limited. Here we report the generation of over 14,000 amiRNA-expressing plants that enable screens of the functionally redundant gene space in Arabidopsis . A protocol is developed here for isolating robust and reproducible amiRNA-mutants. Examples of validation approaches and essential controls are presented for two new amiRNA mutants that exhibit genetically redundant phenotypes and circumvent double mutant lethality. In a forward genetic screen for abscisic acid (ABA)-mediated inhibition of seed germination, amiRNAs that target combinations of known redundant ABA receptor and SnRK2 kinase genes were rapidly isolated, providing a strong proof of principle for this approach. A new ABA insensitive amiRNA line is isolated, which targets three genes encoding avirulence-induced gene2-like ( AIG2 ) genes. A thermal imaging screen for plants with impaired stomatal opening in response to low CO 2 exposure led here to isolation of a new amiRNA targeting two essential proteasomal subunits, PAB1 and PAB2. The seed library of 14,000 T2 amiRNA lines generated here provides a new platform for forward genetic screens and is being made available to the Arabidopsis Biological Resource Center (ABRC) and optimized procedures for amiRNA screening and controls are described.