TheArabidopsis OBERON1andOBERON2genes encode plant homeodomain finger proteins and are required for apical meristem maintenance

Abstract

Maintenance of the stem cell population located at the apical meristems is essential for repetitive organ initiation during the development of higher plants. Here, we have characterized the roles of OBERON1 (OBE1) and its paralog OBERON2 (OBE2), which encode plant homeodomain finger proteins, in the maintenance and/or establishment of the meristems in Arabidopsis. Although the obe1 and obe2 single mutants were indistinguishable from wild-type plants, the obe1 obe2 double mutant displayed premature termination of the shoot meristem, suggesting that OBE1 and OBE2 function redundantly. Further analyses revealed that OBE1 and OBE2 allow the plant cells to acquire meristematic activity via the WUSCHEL-CLAVATA pathway, which is required for the maintenance of the stem cell population, and they function parallel to the SHOOT MERISTEMLESS gene, which is required for preventing cell differentiation in the shoot meristem. In addition, obe1 obe2 mutants failed to establish the root apical meristem, lacking both the initial cells and the quiescent center. In situ hybridization revealed that expression of PLETHORA and SCARECROW, which are required for stem cell specification and maintenance in the root meristem, was lost from obe1 obe2 mutant embryos. Taken together, these data suggest that the OBE1 and OBE2 genes are functionally redundant and crucial for the maintenance and/or establishment of both the shoot and root meristems.

Characterization of EMU, the Arabidopsis homolog of the yeast THO complex member HPR1

“…1F,G). Such defects in cell division were not observed in wild-type embryos and were previously described in other genetic backgrounds that alter the cotyledon number (Saiga et al 2008;Ploense et al 2009). Furthermore, the leaves of emu plants exhibited a more serrated margin than wild-type plants during later developmental stages (Fig.…”

Auxin Control of Embryo Patterning

“…Correct control of MP-dependent root initiation may also involve chromatin regulation, as mutations in the plant homeodomain finger (PHD) proteins OBERON (OBE) 1 and 2 affect root meristem initiation (Saiga et al 2008;Thomas et al 2009). obe1 obe2 double mutants show aberrant hypophysis division and are rootless (Fig.…”

Control of embryonic meristem initiation in Arabidopsis by PHD-finger protein complexes

“…The tta1-1 (SALK_042597), tta2-1 (SALK_082338) and tta2-2 (SALK_016218) mutants were obtained from the Arabidopsis Biological Resource Center (ABRC). obe1 and obe2 mutants, OBE1p::OBE1-GFP, TMO5p::3ϫnGFP and TMO7p::3ϫnGFP transgenic lines have been described previously (Saiga et al, 2008;Schlereth et al, 2010). Plants were grown on MS agar plates containing 1% sucrose or on rock-wool bricks surrounded by vermiculite under long-day conditions (16 hours light/8 hours dark) at 22°C.…”

“…OBERON1 (OBE1) and OBE2 genes encode plant homeodomain (PHD)-finger proteins and these genes act redundantly in MP-dependent embryonic root initiation (Saiga et al, 2008;Thomas et al, 2009). The PHD-finger domain is found in a wide variety of proteins involved in the regulation of chromatin structure (Taverna et al, 2007).…”

“…Interestingly, although PLT1, PLT2, SCR and WOX5 are not expressed in obe1 obe2 double-mutant embryos, MP is normally expressed. As expression of PLT1, PLT2 and WOX5 depends on MP (Aida et al, 2004;Sarker et al, 2007), one possibility is that OBE1 and OBE2 act to control embryonic root meristem formation downstream or at the level of MP (Saiga et al, 2008). However, the function of OBE proteins in the MP pathway is not known.…”