What a tangled web it weaves: auxin coordination of stem cell maintenance and flower production.

Robust agricultural yields require consistent flower production throughout fluctuating environmental conditions. Floral primordia are produced in the inflorescence meristem, which contains a pool of continuously dividing stem cells. Daughter cells of these divisions either retain stem cell identity or are pushed to the SAM periphery, where they become competent to develop into floral primordia after receiving the appropriate signal.

A network of CLAVATA receptors buffers auxin-dependent meristem maintenance.

Plant body plans are elaborated in response to both environmental and endogenous cues. How these inputs intersect to promote growth and development remains poorly understood. During reproductive development, central zone stem cell proliferation in inflorescence meristems is negatively regulated by the CLAVATA3 (CLV3) peptide signalling pathway.

RGI-GOLVEN signaling promotes cell surface immune receptor abundance to regulate plant immunity.

Plant immune responses must be tightly controlled for proper allocation of resources for growth and development. In plants, endogenous signaling peptides regulate developmental and growth-related processes. Recent research indicates that some of these peptides also have regulatory functions in the control of plant immune responses.

WOX going on: CLE peptides in plant development.

The development of plant tissues requires cell-cell communication facilitated by chemical and peptide hormones, including small signaling peptides in the CLAVATA3/EMBRYO-SURROUNDING REGION (CLE) family. The paradigmatic CLE signaling peptide CLAVATA3 regulates the size of the shoot apical meristem and the expression of the stem cell-promoting WUSCHEL transcription factor through an unknown mechanism. This review discusses recent advances in CLE signaling, showing that CLE pathways are conserved in bryophytes, that CLE peptides in Arabidopsis thaliana regulate stem cell identity and cell division in root tissues, and connections to auxin biosynthesis in regulating flower and leaf development.

BAM1/2 receptor kinase signaling drives CLE peptide-mediated formative cell divisions in roots.

Cell division is often regulated by extracellular signaling networks to ensure correct patterning during development. In , the SHORT-ROOT (SHR)/SCARECROW (SCR) transcription factor dimer activates ; () to drive formative divisions during root ground tissue development. Here, we show plasma-membrane-localized BARELY ANY MERISTEM1/2 (BAM1/2) family receptor kinases are required for -dependent formative divisions and expression, but not -dependent ground tissue specification.

Auxin-Regulated Reversible Inhibition of TMK1 Signaling by MAKR2 Modulates the Dynamics of Root Gravitropism.

Plants are able to orient their growth according to gravity, which ultimately controls both shoot and root architecture. Gravitropism is a dynamic process whereby gravistimulation induces the asymmetric distribution of the plant hormone auxin, leading to asymmetric growth, organ bending, and subsequent reset of auxin distribution back to the original pre-gravistimulation situation. Differential auxin accumulation during the gravitropic response depends on the activity of polarly localized PIN-FORMED (PIN) auxin-efflux carriers.

CLAVATA Signaling Ensures Reproductive Development in Plants across Thermal Environments.

The ability to thrive in diverse environments requires that species maintain development and reproduction despite dynamic conditions. Many developmental processes are stabilized through robust signaling pathways that cooperatively ensure proper development. During reproduction, plants like Arabidopsis thaliana continuously generate flowers on growing indeterminate inflorescences.

The HK5 and HK6 cytokinin receptors mediate diverse developmental pathways in rice.

The phytohormone cytokinin regulates diverse aspects of plant growth and development. Our understanding of the metabolism and perception of cytokinin has made great strides in recent years, mostly from studies of the model dicot Here, we employed a CRISPR/Cas9-based approach to disrupt a subset of cytokinin histidine kinase (HK) receptors in rice () in order to explore the role of cytokinin in a monocot species. In and single mutants, the root growth, leaf width, inflorescence architecture and/or floral development were affected.

GOLVEN peptide signalling through RGI receptors and MPK6 restricts asymmetric cell division during lateral root initiation.

During lateral root initiation, lateral root founder cells undergo asymmetric cell divisions that generate daughter cells with different sizes and fates, a prerequisite for correct primordium organogenesis. An excess of the GLV6/RGF8 peptide disrupts these initial asymmetric cell divisions, resulting in more symmetric divisions and the failure to achieve lateral root organogenesis. Here, we show that loss-of-function GLV6 and its homologue GLV10 increase asymmetric cell divisions during lateral root initiation, and we identified three members of the RGF1 INSENSITIVE/RGF1 receptor subfamily as likely GLV receptors in this process.

A PXY-Mediated Transcriptional Network Integrates Signaling Mechanisms to Control Vascular Development in Arabidopsis.

The cambium and procambium generate the majority of biomass in vascular plants. These meristems constitute a bifacial stem cell population from which xylem and phloem are specified on opposing sides by positional signals. The PHLOEM INTERCALATED WITH XYLEM (PXY) receptor kinase promotes vascular cell division and organization.

Using indCAPS to Detect CRISPR/Cas9 Induced Mutations.

Cleaved amplified polymorphic sequences (CAPS) assays are useful tools for detecting small mutations such as single nucleotide polymorphisms (SNPs) or insertion/deletions (indels) present in an amplified DNA fragment. A mutation that disrupts or creates a restriction site will prevent cleavage by a restriction enzyme, allowing discrimination of wild-type and mutant alleles. In cases where no convenient restriction site is present, a derived Cleaved Amplified Polymorphic Sequence (dCAPS) assay can be used, where mismatches in the primer are used to create a diagnostic restriction site.

Type-B response regulators of rice play key roles in growth, development and cytokinin signaling.

Cytokinins are plant hormones with crucial roles in growth and development. Although cytokinin signaling is well characterized in the model dicot , we are only beginning to understand its role in monocots, such as rice () and other cereals of agronomic importance. Here, we used primarily a CRISPR/Cas9 gene-editing approach to characterize the roles of a key family of transcription factors, the type-B response regulators (RRs), in cytokinin signaling in rice.

Evolution of buffering in a genetic circuit controlling plant stem cell proliferation.

Precise control of plant stem cell proliferation is necessary for the continuous and reproducible development of plant organs. The peptide ligand CLAVATA3 (CLV3) and its receptor protein kinase CLAVATA1 (CLV1) maintain stem cell homeostasis within a deeply conserved negative feedback circuit. In Arabidopsis, CLV1 paralogs also contribute to homeostasis, by compensating for the loss of CLV1 through transcriptional upregulation.

Modulation of Asymmetric Division Diversity through Cytokinin and SPEECHLESS Regulatory Interactions in the Arabidopsis Stomatal Lineage.

Coordinated growth of organs requires communication among cells within and between tissues. In plants, leaf growth is largely dictated by the epidermis; here, asymmetric and self-renewing divisions of the stomatal lineage create two essential cell types-pavement cells and guard cells-in proportions reflecting inputs from local, systemic, and environmental cues. The transcription factor SPEECHLESS (SPCH) is the prime regulator of divisions, but whether and how it is influenced by external cues to provide flexible development is enigmatic.

CLAVATA Was a Genetic Novelty for the Morphological Innovation of 3D Growth in Land Plants.

How genes shape diverse plant and animal body forms is a key question in biology. Unlike animal cells, plant cells are confined by rigid cell walls, and cell division plane orientation and growth rather than cell movement determine overall body form. The emergence of plants on land coincided with a new capacity to rotate stem cell divisions through multiple planes, and this enabled three-dimensional (3D) forms to arise from ancestral forms constrained to 2D growth.

Cutting Edge Genetics: CRISPR/Cas9 Editing of Plant Genomes.

The clustered regularly interspaced short palindromic repeat (CRISPR)/CRISPR-associated nuclease 9 (Cas9) system is a genome editing technology transforming the field of plant biology by virtue of the system's efficiency and specificity. The system has quickly evolved for many diverse applications including multiplex gene mutation, gene replacement and transcriptional control. As CRISPR/Cas9 is increasingly applied to plants, it is becoming clear that each component of the system can be modified to improve editing results.

CRISPR/Cas9-mediated resistance to cauliflower mosaic virus.

Viral diseases are a leading cause of worldwide yield losses in crop production. Breeding of resistance genes ( gene) into elite crop cultivars has been the standard and most cost-effective practice. However, gene-mediated resistance is limited by the available genes within genetic resources and in many cases, by strain specificity.

Somatic hybridization provides segregating populations for the identification of causative mutations in sterile mutants of the moss Physcomitrella patens.

Forward genetics is now straightforward in the moss Physcomitrella patens, and large mutant populations can be screened relatively easily. However, perturbation of development before the formation of gametes currently leaves no route to gene discovery. Somatic hybridization has previously been used to rescue sterile mutants and to assign P.

indCAPS: A tool for designing screening primers for CRISPR/Cas9 mutagenesis events.

Genetic manipulation of organisms using CRISPR/Cas9 technology generally produces small insertions/deletions (indels) that can be difficult to detect. Here, we describe a technique to easily and rapidly identify such indels. Sequence-identified mutations that alter a restriction enzyme recognition site can be readily distinguished from wild-type alleles using a cleaved amplified polymorphic sequence (CAPS) technique.

Gateway-Compatible CRISPR-Cas9 Vectors and a Rapid Detection by High-Resolution Melting Curve Analysis.

CRISPR-Cas9 system rapidly became an indispensable tool in plant biology to perform targeted mutagenesis. A CRISPR-Cas9-mediated double strand break followed by non-homologous end joining (NHEJ) repair most frequently results in a single base pair deletion or insertions (indels), which is hard to detect using methods based on enzymes that detect heteroduplex DNA. In addition, somatic tissues of the T1 generation inevitably contain a mosaic population, in which the portion of cells carrying the mutation can be too small to be detected by the enzyme-based methods.