OBE3 and WUS Interaction in Shoot Meristem Stem Cell Regulation

Abstract

The stem cells in the shoot apical meristem (SAM) are the origin of all above ground tissues in plants. In Arabidopsis thaliana, shoot meristem stem cells are maintained by the homeobox transcription factor gene WUS (WUSCHEL) that is expressed in cells of the organizing center underneath the stem cells. In order to identify factors that operate together with WUS in stem cell maintenance, we performed an EMS mutant screen for modifiers of the hypomorphic wus-6 allele. We isolated the oberon3-2 (obe3-2) mutant that enhances stem cell defects in wus-6, but does not affect the putative null allele wus-1. The OBE3 gene encodes a PHD (Plant Homeo Domain) protein that is thought to function in chromatin regulation. Single mutants of OBE3 or its closest homolog OBE4 do not display any defects, whereas the obe3-2 obe4-2 double mutant displays broad growth defects and developmental arrest of seedlings. Transcript levels of WUS and its target gene in the stem cells, CLAVATA3, are reduced in obe3-2. On the other hand, OBE3 and OBE4 transcripts are both indirectly upregulated by ectopic WUS expression. Our results suggest a positive feedback regulation between WUS and OBE3 that contributes to shoot meristem homeostasis.

OBERON3 and SUPPRESSOR OF MAX2 1-LIKE proteins form a regulatory module specifying phloem identity

“…Judging from the protein domains and sub-nuclear localization, we hypothesize that SMXL3/4/5 and OBE3 form a protein complex that is involved in chromatin remodeling and/or transcriptional regulation of downstream targets. Similar to the previous report on the OBE3-WUS interaction in the SAM (Lin et al 2016), we cannot rule out that other OBE family members apart from OBE3 interact with SMXL3/4/5 in protophloem formation. Although all mutant alleles used in this study were reported to be functional knock-outs because multiple mutants show strong embryonic defects Saiga et al 2012), residual activity of the OBE1, OBE2 or OBE4 genes might be sufficient to support SMXL3/4/5 activity.…”

“…In contrast to SMXL proteins whose activity is spatially highly restricted, OBERONs (OBEs) are a family of four ubiquitously expressed, nuclear-localized proteins essential for tissue specification and meristem maintenance starting from the earliest stages of embryo development (Saiga et al 2008;Thomas et al 2009;Saiga et al 2012;Lin et al 2016). This role is reflected by mutants deficient for either of the two OBE sub-families which are embryo lethal (Saiga et al 2008;Thomas et al 2009;Saiga et al 2012).…”

Global Analysis of WOX Transcription Factor Gene Family in Brassica napus Reveals Their Stress- and Hormone-Responsive Patterns

“…CLE peptides are a well-known group of post-translationally modified signal molecules involved in cell division in SAM, the root apical meristem (RAM) and vascular meristem, which can respond to stress signals [ 10 , 33 , 34 ]. Previous reports have demonstrated that AtWUS, AtWOX4, AtWOX5 and AtWOX14 can regulate cell division in SAM, vascular meristem and RAM [ 10 , 35 ], respectively, while WUS–CLV interactions were shown to establish a feedback loop between stem cells and the underlying regulatory center [ 7 ]. In addition, the results of the present study showed that AtWOXs could interact with some TFs, such as GRAS, SCR and SHR ( Table S7 ).…”

A comprehensive physical interaction map between the Turnip mosaic potyvirus and Arabidopsis thaliana proteomes

“…The interaction between VPg and OBE1 (an evolutionarily conserved hub in the host proteome) is suggestive, as this protein is involved in the establishment and maintenance of the shoot and root apical meristems through the regulation of the expression of the stem cell factor WUSCHEL (WUS). Notice that VPg also interacts with the PDH fingers OBERON 2 (OBE2), an element that functions like OBE1 [71], and OBERON 3 (OBE3), one of the transcriptional activators of WUS and the CLAVATA (CLV) pathway [72]. By looking at the interactors of OBE1 in the network, we found OBE3, STOMATAL CLOSURE-RELATED ACTIN BINDING 1 (SCAB1), which stabilizes actin filaments and controls stomatal movement [73], and various WRKY transcription factors, which activate the expression of defense genes against pathogens [74].…”