| Increasing evidence from animal and yeast systems demonstrates the importance of long coiled-coil proteins in a variety of cellular processes. Yet, functional knowledge about long coiled-coil proteins in plants is sparse. In this study I present the functional characterization of a family of two plant-specific long coiled-coil proteins, PAMP INDUCED COILED-COIL (PICC) and PICC-LIKE (PICL) in Arabidopsis. I employed an in-depth multi-dimensional approach using cell and molecular biology, biochemistry, reverse genetics, and in silico analyses to gain insight into their function. PICC and PICL are anchored to the membranes of the endoplasmic reticulum by a C-terminal transmembrane domain and a short tail domain, via a tail-anchoring mechanism. PICC expression is induced by bacterial pathogen associated molecular patterns (PAMPs) and loss of function mutants of PICC are compromised in PAMP triggered immunity (PTI), which is the primary layer of defense against pathogens in plants. PICL is neither induced by PAMPs nor involved in PTI, suggesting functional diversification of these paralogous genes. However, PICC and PICL appear to play a role in post-germination growth response to the plant abiotic stress hormone abscissic acid (ABA). Next, using yeast two-hybrid and membrane yeast two-hybrid library screens, I identified a TETRATRICOPEPTIDE PROTEIN (TP) and GLUTAMYL t-RNA SYNTHETASE (GluRS) as putative interacting partners for PICC and PICL, respectively. They can now form the nodes for expanding the PICC and PICL interaction networks. The data presented here provide the first evidence for the involvement of a plant long coiled-coil protein in a plant defense response. Orthologs of PICC and PICL are present in agronomically important crops such as rice and sorghum and can thus be explored towards the goal of developing disease resistant crops. |
