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Abstract

Plant organs, such as leaves and flowers, arise through cellular division events that are precisely coordinated between both adjacent, related cells and across distinct cell layers. Receptor-like kinases are cell surface receptors that perceive and relay intercellular information. In Arabidopsis, the receptor-like kinase STRUBBELIG has been shown to mediate inter-cell layer communication during floral development, amongst other functions; little is known, however, concerning its exact signaling mechanism. In order to identify additional molecular components involved in SUB-dependent signaling processes, we used forward genetics and identified recessive mutations in three genes that result in a sub-like phenotype. Plants with a defect in DETORQUEO (DOQ), QUIRKY (QKY), and ZERZAUST (ZET) show corresponding defects in outer integument development, floral organ shape and stem twisting, and also show sub-like cellular defects in the floral meristem and roots. Thus, SUB, DOQ, QKY, and ZET define the STRUBBELIG-LIKE MUTANT (SLM) class of genes. Morphological analysis of single and double mutants indicated that SLM genes have overlapping, but also distinct, functions in plant organogenesis. Systematic comparison of whole-genome transcript profiles defined common and distinct sets of transcriptional targets in slm mutants, thus supporting this notion. Here we describe the molecular nature of QUIRKY: the encoded protein is likely membrane-localized and predicted to require Ca 2+ for activity. Our current hypothesis is that QUIRKY facilitates transport of molecules to the cell boundary and may support a STRUBBELIG-related extracellular signal.