Abstract
Receptor endocytosis is important for signal activation, transduction, and deactivation. However, how a receptor interprets conflicting signals to adjust cellular output is not clearly understood. Using genetic, cell biological, and pharmacological approaches, we report here that ERECTA-LIKE1 (ERL1), the major receptor restricting plant stomatal differentiation, undergoes dynamic subcellular behaviors in response to different EPIDERMAL PATTERNING FACTOR (EPF) peptides. Activation of ERL1 by EPF1 induces rapid ERL1 internalization via multivesicular bodies/late endosomes to vacuolar degradation, whereas ERL1 constitutively internalizes in the absence of EPF1. The co-receptor, TOO MANY MOUTHS is essential for ERL1 internalization induced by EPF1 but not by EPFL6. The peptide antagonist, Stomagen, triggers retention of ERL1 in the endoplasmic reticulum, likely coupled with reduced endocytosis. In contrast, the dominant-negative ERL1 remained dysfunctional in ligand-induced subcellular trafficking. Our study elucidates that multiple related yet unique peptides specify cell fate by deploying the differential subcellular dynamics of a single receptor.
Highlights
39 40 Receptor-mediated endocytosis is an integral part of cellular signaling, as it mediates signal attenuation and provides spatial and temporal dimensions to signaling events
Our study shows that EPF1 and EPFL6, the ligands activating the 91 inhibitory stomatal signaling, trigger ERL1 endocytosis into multivesicular bodies (MVB)
Our study reveals a mechanism by which plant cells interpret multiple signals through the subcellular localization and trafficking route of a single receptor. 100 101 Results 102 103 ERL1 is internalized through multivesicular bodies to vacuolar pathway in stomatal meristemoids To understand how stomatal cell fate decisions are made at the level of receptor subcellular dynamics, we first examined the localization of ERL1 (Figure 1)
Summary
39 40 Receptor-mediated endocytosis is an integral part of cellular signaling, as it mediates signal attenuation and provides spatial and temporal dimensions to signaling events. Endocytosis of receptor tyrosine kinases can attenuate the signal outputs, by removing the active receptor pools from the plasma membrane, or it can specify signals at defined sites of action, such as signaling through endosomes (Sigismund et al, 2012). In Arabidopsis, bacterial flagellin peptide flg induces the heterodimer formation consisting of the LRR-RLKs FLAGELLIN SENSING2 (FLS2) and BRI153 ASSOCIATED RECEPTOR KINASE (BAK1)/SOMATIC EMBRYOGENESIS RECEPTOR LIKE KINASE 3 (Chinchilla et al, 2007). This triggers the endocytosis and degradation of the complex to generate transient cellular immune signaling and to prevent continuous signaling to the same stimulus (Robatzek et al, 2006; Beck et al, 2012). It remains a key question as to where within the cell these LRR-RLKs transduce signals and how different 65 activation states of LRR-RLKs influence their subcellular localization
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