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Abstract

Tissue morphogenesis in plants requires the coordination of cellular behavior within and across clonally distinct histogenic layers. In Arabidopsis, the leucine-rich repeat receptor-like kinase STRUBBELIG (SUB) is required for inter-cell-layer communication during floral and ovule development. SUB is an atypical receptor-like kinase that when mutated, shows defects in floral organ, stem and silique shape, ovule integument morphogenesis and root hair patterning. SUB affects tissue morphogenesis in a non cell-autonomous manner thus influencing the behavior of neighboring cells. QUIRKY (QKY), ZERZAUST (ZET) and ANGUSTIFOLIA (AN) belong to STRUBBELIG-LIKE MUTANT (SLM) class of genes, proposed to contribute to SUB-dependent signal transduction. In the present work, molecular characterization of QKY was undertaken with the main focus on its role in SUB mediated signaling. Mapping and molecular identification of QKY revealed that it encodes a novel multiple C2 domain-containing transmembrane protein (MCTP). Biochemical studies imply that QKY binds to phospholipids in a Ca+2 dependent manner. Protein localization experiments indicate that QKY is specifically associated with plasmodesmata (PD). Immunogold electron microscopy results confirm the PD localization of QKY and also reveal the previously unknown PD localization of SUB. SUB and QKY do not appear to be involved in non-selective movement GFP-sized proteins. Yeast-two-hybrid data indicate that SUB and QKY can interact directly. Thus, the data imply that SUB signaling mediates tissue morphogenesis by influencing selective transport of molecules through PD.