Nuclear import of the transcription factor SHOOT MERISTEMLESS depends on heterodimerization with BLH proteins expressed in discrete sub-domains of the shoot apical meristem of Arabidopsis thaliana

Abstract

The gene SHOOT MERISTEMLESS (STM) is required for the initiation and the maintenance of the shoot apical meristem (SAM) in Arabidopsis and encodes a MEINOX/three amino acid loop extension (TALE)-HD-type transcription factor. Translational fusions with the green fluorescent protein showed that STM is not nuclear by default. In a yeast two-hybrid screen performed with a meristem-enriched cDNA library, three interacting BLH (Bel1-like homeodomain) transcription factors were identified. According to bimolecular fluorescence complementation, STM is targeted into the nuclear compartment through heterodimerization with BLH partner proteins, which are expressed in distinct SAM domains from the center to the periphery. On a functional level, overexpression experiments in transgenic Arabidopsis plants suggest that individual heterodimers provide distinct contributions. These results contribute to our understanding of the STM transcription factor function in the SAM and also shed new light on the evolution of the TALE-HD super gene family in animal and plant lineages.

KNOX genes: versatile regulators of plant development and diversity

“…KNOX proteins interact with another group of TALE proteins, the BEL1-like homeodomain family (BELL or BLH, see Table 2), in a highly connected, complex network that determines not only high-affinity KNOX target selection but also their subcellular localization (Bellaoui et al, 2001;Bhatt et al, 2004;Cole et al, 2006;Hackbusch et al, 2005;Smith et al, 2002). These interactions depend on the KNOX MEINOX domain, and each homeodomain of the two proteins binds to target DNA as a protein heterodimer (Box 3).…”

Transcriptomic Analyses Indicate That Maize Ligule Development Recapitulates Gene Expression Patterns That Occur during Lateral Organ Initiation

“…Given the proposed role of KNOX in leaf proximal-distal patterning, we investigated genes that are DE in our data and are also bound and modulated by KN1 protein (Bolduc et al, 2012b). In Arabidopsis, BEL1-like homeodomain (BELL) proteins form heterodimers with KNOX proteins in combinations that determine target selection and subcellular localization (Bellaoui Smith et al, 2002;Bhatt et al, 2004;Hackbusch et al, 2005;Cole et al, 2006). Our data show that maize bel12 (GRMZM2G154641) is significantly upregulated in the preligule region, whereas bel14 (GRMZM2G125976) is expressed at low levels in the blade, moderate levels in the sheath, and most highly in the ligule region ( Figure 4G; Supplemental Table 4).…”

The AP2 transcription factors DORNRÖSCHEN and DORNRÖSCHEN-LIKE redundantly controlArabidopsisembryo patterning via interaction with PHAVOLUTA

“…For control experiments, GFP fusions were created in the pRT-⍀NotI/AscI vector (Überlacker and Werr, 1996). Transient expression in leek epidermal cells was performed according to Cole et al (Cole et al, 2006). YFP/GFP fluorescence was visualised using a MZFLIII stereomicroscope (Leica) after UV excitation and using a GFP filter.…”