Biomedical subjects

Renze Heidstra

Publications and source records attributed to Renze Heidstra.

11 recordsLinked to original sources

PubMed2006

Vectorial information for Arabidopsis planar polarity is mediated by combined AUX1, EIN2, and GNOM activity.

Cell polarity is commonly coordinated within the plane of a single tissue layer (planar polarity), and hair positioning has been exploited as a simple marker for planar polarization of animal epithelia . The root epidermis of the plant Arabidopsis similarly reveals planar polarity of hair localization close to root tip-oriented (basal) ends of hair-forming cells . Hair position is directed toward a concentration maximum of the hormone auxin in the root tip , but mechanisms driving this plant-specific planar polarity remain elusive. Here, we report that combinatorial action of the auxin influx carrier AUX1, ETHYLENE-INSENSITIVE2 (EIN2) , and GNOM genes mediates the vector for coordinate hair positioning. In aux1;ein2;gnom eb triple mutant roots, hairs display axial (apical or basal) instead of coordinate polar (basal) position, and recruitment of Rho-of-Plant (ROP) GTPases to the hair initiation site reveals the same polar-to-axial switch. The auxin concentration gradient is virtually abolished in aux1;ein2;gnom eb roots, where locally applied auxin can coordinate hair positioning. Moreover, auxin overproduction in sectors of wild-type roots enhances planar ROP and hair polarity over long and short distances. Hence, auxin may provide vectorial information for planar polarity that requires combinatorial AUX1, EIN2, and GNOM activity upstream of ROP positioning.

Arabidopsis↗

PubMed2006

Non-cell-autonomous rescue of anaphase-promoting complex function revealed by mosaic analysis of HOBBIT, an Arabidopsis CDC27 homolog.

The Arabidopsis HOBBIT (HBT) gene encodes a homolog of the CDC27 anaphase-promoting complex/cyclosome subunit and is essential for postembryonic development. We induced loss-of-function clones by Cre/lox-mediated recombination of a single complementing HBT transgene in a background homozygous for the strong mutant allele hbt(2311). Defects in cell division and cell expansion are the primary consequences of ubiquitous postembryonic HBT excision. In roots, both cell division and cell expansion are rapidly affected. In contrast, in leaf primordia, cell division and cell expansion halt after a lag phase, which results in different severities of defects in the proximodistal and mediolateral axes. Surprisingly, small clones reveal non-cell-autonomous rescue of hbt mutant cells, indicating a previously unrecognized compensation mechanism for reduced activity of an anaphase-promoting complex/cyclosome component critical for cell cycle progression.

Anaphase-Promoting Complex-Cyclosome↗

PubMed2006

A molecular framework for plant regeneration.

Plants and some animals have a profound capacity to regenerate organs from adult tissues. Molecular mechanisms for regeneration have, however, been largely unexplored. Here we investigate a local regeneration response in Arabidopsis roots. Laser-induced wounding disrupts the flow of auxin-a cell-fate-instructive plant hormone-in root tips, and we demonstrate that resulting cell-fate changes require the PLETHORA, SHORTROOT, and SCARECROW transcription factors. These transcription factors regulate the expression and polar position of PIN auxin efflux-facilitating membrane proteins to reconstitute auxin transport in renewed root tips. Thus, a regeneration mechanism using embryonic root stem-cell patterning factors first responds to and subsequently stabilizes a new hormone distribution.

Arabidopsis↗

PubMed2005

The RETINOBLASTOMA-RELATED gene regulates stem cell maintenance in Arabidopsis roots.

The maintenance of stem cells in defined locations is crucial for all multicellular organisms. Although intrinsic factors and signals for stem cell fate have been identified in several species, it has remained unclear how these connect to the ability to reenter the cell cycle that is one of the defining properties of stem cells. We show that local reduction of expression of the RETINOBLASTOMA-RELATED (RBR) gene in Arabidopsis roots increases the amount of stem cells without affecting cell cycle duration in mitotically active cells. Conversely, induced RBR overexpression dissipates stem cells prior to arresting other mitotic cells. Overexpression of D cyclins, KIP-related proteins, and E2F factors also affects root stem cell pool size, and genetic interactions suggest that these factors function in a canonical RBR pathway to regulate somatic stem cells. Expression analysis and genetic interactions position RBR-mediated regulation of the stem cell state downstream of the patterning gene SCARECROW.

Arabidopsis↗

PubMed2005

The 14-amino acid CLV3, CLE19, and CLE40 peptides trigger consumption of the root meristem in Arabidopsis through a CLAVATA2-dependent pathway.

CLAVATA3 (CLV3), CLV3/ESR19 (CLE19), and CLE40 belong to a family of 26 genes in Arabidopsis thaliana that encode putative peptide ligands with unknown identity. It has been shown previously that ectopic expression of any of these three genes leads to a consumption of the root meristem. Here, we show that in vitro application of synthetic 14-amino acid peptides, CLV3p, CLE19p, and CLE40p, corresponding to the conserved CLE motif, mimics the overexpression phenotype. The same result was observed when CLE19 protein was applied externally. Interestingly, clv2 failed to respond to the peptide treatment, suggesting that CLV2 is involved in the CLE peptide signaling. Crossing of the CLE19 overexpression line with clv mutants confirms the involvement of CLV2. Analyses using tissue-specific marker lines revealed that the peptide treatments led to a premature differentiation of the ground tissue daughter cells and misspecification of cell identity in the pericycle and endodermis layers. We propose that these 14-amino acid peptides represent the major active domain of the corresponding CLE proteins, which interact with or saturate an unknown cell identity-maintaining CLV2 receptor complex in roots, leading to consumption of the root meristem.

Amino Acid Sequence↗

PubMed2005

The PIN auxin efflux facilitator network controls growth and patterning in Arabidopsis roots.

Local accumulation of the plant growth regulator auxin mediates pattern formation in Arabidopsis roots and influences outgrowth and development of lateral root- and shoot-derived primordia. However, it has remained unclear how auxin can simultaneously regulate patterning and organ outgrowth and how its distribution is stabilized in a primordium-specific manner. Here we show that five PIN genes collectively control auxin distribution to regulate cell division and cell expansion in the primary root. Furthermore, the joint action of these genes has an important role in pattern formation by focusing the auxin maximum and restricting the expression domain of PLETHORA (PLT) genes, major determinants for root stem cell specification. In turn, PLT genes are required for PIN gene transcription to stabilize the auxin maximum at the distal root tip. Our data reveal an interaction network of auxin transport facilitators and root fate determinants that control patterning and growth of the root primordium.

Arabidopsis↗

PubMed2004

The PLETHORA genes mediate patterning of the Arabidopsis root stem cell niche.

A small organizing center, the quiescent center (QC), maintains stem cells in the Arabidopsis root and defines the stem cell niche. The phytohormone auxin influences the position of this niche by an unknown mechanism. Here, we identify the PLETHORA1 (PLT1) and PLT2 genes encoding AP2 class putative transcription factors, which are essential for QC specification and stem cell activity. The PLT genes are transcribed in response to auxin accumulation and are dependent on auxin response transcription factors. Distal PLT transcript accumulation creates an overlap with the radial expression domains of SHORT-ROOT and SCARECROW, providing positional information for the stem cell niche. Furthermore, the PLT genes are activated in the basal embryo region that gives rise to hypocotyl, root, and root stem cells and, when ectopically expressed, transform apical regions to these identities. Thus, the PLT genes are key effectors for establishment of the stem cell niche during embryonic pattern formation.

Arabidopsis↗

PubMed2004

Mosaic analyses using marked activation and deletion clones dissect Arabidopsis SCARECROW action in asymmetric cell division.

In the Arabidopsis root meristem, ground tissue stem cell daughters perform an asymmetric division to form endodermis and cortex. The putative transcription factors SCARECROW (SCR) and SHORTROOT (SHR) regulate this radial patterning event, and the mixed cell fate in scr mutants suggests an atypical role of the SCR gene in asymmetric cell division. Here we use a newly developed site-specific gene activation/deletion system in which induced clones are positively marked with green fluorescent protein (GFP). Using this system, we show that SCR acts cell-autonomously to control asymmetric cell division within the ground tissue. We provide evidence that SCR gene expression is under autoregulatory control, that SCR limits SHR movement, and that transient SCR action is sufficient to separate endodermis and cortex fates by asymmetric cell division.

Arabidopsis↗

PubMed2004

Root genomics: towards digital in situ hybridization.

Separation of cell types and developmental stages in the Arabidopsis root and subsequent expression profiling have yielded a valuable dataset that can be used to select candidate genes for detailed study and to start probing the complexities of gene regulation in plant development.

Computers↗

PubMed2003

Root-specific CLE19 overexpression and the sol1/2 suppressors implicate a CLV-like pathway in the control of Arabidopsis root meristem maintenance.

In the Arabidopsis shoot apical meristem, an organizing center signals in a non-cell-autonomous manner to specify the overlying stem cells. Stem cells express the small, secreted protein CLAVATA3 (CLV3; ) that activates the CLV1-CLV2 receptor complex, which negatively controls the size of the organizing center. Consistently, CLV3 overexpression restricts shoot meristem size. The root meristem also contains a stem cell organizer, and here we show that localized overexpression in roots of CLE19, encoding a CLV3 homolog, restricts the size of the root meristem. This suggests that CLE19 acts by overactivating an endogenous CLV-like pathway involved in root meristem maintenance. Surprisingly, CLE19 restricts meristem size without directly interfering with organizer and stem cell specification. We isolated mutations in two loci, SOL1 and SOL2, which suppress the CLE19 overexpression phenotype. sol2 plants display floral phenotypes reminiscent of clv weak alleles; these phenotypes suggest that components of a CLV pathway are shared in roots and shoots. SOL1 encodes a putative Zn(2+)-carboxypeptidase, which may be involved in ligand processing.

Amino Acid Sequence↗

PubMed2003

SCARECROW is involved in positioning the stem cell niche in the Arabidopsis root meristem.

Stem cells self-renew and produce daughter cells that differentiate. How stem cells are specified and maintained is a central question in developmental biology. Plant stem cells occupy a small region or niche in larger zones of mitotic activity called meristems. Here we provide molecular evidence that in the Arabidopsis root meristem, the stem cell population depends on a central group of cells, the quiescent center (QC), which positions the stem cell niche. We show that the putative transcription factor SCARECROW (SCR), first identified by its role in radial patterning, is required cell-autonomously for distal specification of the QC, which in turn regulates stem cell fate of immediately surrounding cells.

Arabidopsis↗