Mechanistic insight into a peptide hormone signaling complex mediating floral organ abscission
Authors: Ulrich Hohmann
Julia Santiago
Mari Wildhagen
Benjamin Brandt
Ludwig A Hothorn
Michael Hothorn
Melinka A Butenko
Journal: eLife (2016)
Discipline: BIOLOGY & BIOCHEMISTRY
Keywords: <i>a. thaliana</i>; biophysics; floral abscission; membrane signaling; peptide hormone
Affiliations: Structural Plant Biology Laboratory, Department of Botany and Plant Biology, University of Geneva, Geneva, Switzerland, Department of Biosciences, Section for Genetic and Evolutionary Biology, University of Oslo, Oslo, Norway, Institute of Biostatistics, Leibniz University, Hannover, Germany

Abstract:  Plants constantly renew during their life cycle and thus require to shed senescent and damaged organs. Floral abscission is controlled by the leucine-rich repeat receptor kinase (LRR-RK) HAESA and the peptide hormone IDA. It is unknown how expression of IDA in the abscission zone leads to HAESA activation. Here we show that IDA is sensed directly by the HAESA ectodomain. Crystal structures of HAESA in complex with IDA reveal a hormone binding pocket that accommodates an active dodecamer peptide. A central hydroxyproline residue anchors IDA to the receptor. The HAESA co-receptor SERK1, a positive regulator of the floral abscission pathway, allows for high-affinity sensing of the peptide hormone by binding to an Arg-His-Asn motif in IDA. This sequence pattern is conserved among diverse plant peptides, suggesting that plant peptide hormone receptors may share a common ligand binding mode and activation mechanism. 

Retracted: No

PubPeer comments:
 Fig3D and Fig5A. Although they are representing the same proteins in both figures, the same blot seems to have been reused to demonstrate two independent experiments. ![file] , 
 Dear u201cParus majoru201d, In figure panels 3D and 5A in the manuscript by Santiago et al. we present SDS-PAGE gels (not western blots), depicting the protein content from peak fractions of analytical size-exclusion chromatography experiments. The experiment in figure 3D compares the elution volumes of a receptor u2013 co-receptor - peptide ligand mixture (HAESA-SERK1-Hyp64P; red line in the top panel and corresponding SDS-PAGE lanes peak 1 and 2 in the lower panel) with the elution volumes of two elution volume markers; the isolated LRR domain of the receptor kinase HAESA (black dotted line in the top panel, and corresponding SDS-PAGE lane in the lower panel, both labeled HAESA) and the isolated LRR domain of the co-receptor SERK1 (light-blue dotted line and corresponding SDS-PAGE lane in the lower panel, both labeled SERK1). In order to enable the reader to compare the findings shown in figures 3D (HAESA-SERK1-Hyp64P) and 5A (IDA K66A R67A; IDA DeltaN69), the same elution volume markers are depicted in figure 5A, as clearly stated in the figure legend: u201c(A) Size exclusion chromatography experiments **similar to Figure 3B,D reveal [...] Note that the HAESA and SERK1 input lanes have already been shown in Figure 3D**u201d ![file] Importantly, the experiments shown in Figure 3B and 5D were performed all together by first author Julia Santiago on April 21, 2015, using the same elution volume markers, size-exclusion chromatography column, FPLC device, chromatography running buffer and connecting tubing, in order to minimize elution volume deviations that may otherwise occur due to changes in ionic strength or column-to-detector dead volume, and to allow for comparison of the different experiments, as stated above. In the initial version of the manuscript, the data were all shown in one figure panel (original submission figure S7). ![file] Based on the reviewer comments after the initial submission, I decided to separate mutational analysis of the central hydroxyproline in the IDA peptide ligand (final figure 3 in the published paper) and the mutational analysis of the C-terminal attachment site of IDA in the HAESA-IDA-SERK1 signaling complex (final figure 5 in the published paper). You can find the un-cropped scanned gel picture below for your convenience. ![file] The omission of gel lanes 3-6 in figure panel 3D is clearly indicated by a vertical line. ![file] The statement above u201cFig3D and Fig5A. Although they are representing the same proteins in both figures, the same blot seems to have been reused to demonstrate two independent experiments.u201d is thus factually incorrect. With kind regards, Michael Hothorn Department of Botany and Plant Biology University of Geneva, Switzerland , 
 #2 Dear author, Thank you very much for the clarification and apologies for missing this in the figure legend. ,