The maize aquaporin ZmPIP1;6 enhances stomatal opening and CO2- and ABA-induced stomatal closure.

The plasma membrane aquaporin ZmPIP1;6 is expressed in maize stomatal complexes, with higher expression during the day than at night. To elucidate the role of ZmPIP1;6 in gas exchange and stomatal movement, it was expressed in maize (inbred line B104) under the control of p35S promoter (OE) or its native promoter fused with mYFP cDNA (mYFP-ZmPIP1;6). In stomatal complexes of the leaf mature zone, mYFP-ZmPIP1;6 showed higher expression in subsidiary cells than in guard cells, with light and dark treatments influencing its subcellular localization.

Division Zone Activity Determines the Potential of Drought-Stressed Maize Leaves to Resume Growth after Rehydration.

Drought is one of the most devastating causes of yield losses in crops like maize, and the anticipated increases in severity and duration of drought spells due to climate change pose an imminent threat to agricultural productivity. To understand the drought response, phenotypic and molecular studies are typically performed at a given time point after drought onset, representing a steady-state adaptation response. Because growth is a dynamic process, we monitored the drought response with high temporal resolution and examined cellular and transcriptomic changes after rehydration at 4 and 6 days after leaf four appearance.

ETHYLENE RESPONSE FACTOR6, A Central Regulator of Plant Growth in Response to Stress.

ETHYLENE RESPONSE FACTOR6 (ERF6) has emerged as a central player in stress-induced plant growth inhibition. It orchestrates complex pathways that enable plants to acclimate and thrive in challenging environments. In response to various abiotic and biotic stresses, ERF6 is promptly activated through both ethylene-dependent and -independent pathways, and contributes to enhanced stress tolerance mechanisms by activating a broad spectrum of genes at various developmental stages.

Maize mutant screens: from classical methods to new CRISPR-based approaches.

Mutations play a pivotal role in shaping the trajectory and outcomes of a species evolution and domestication. Maize (Zea mays) has been a major staple crop and model for genetic research for more than 100 yr. With the arrival of site-directed mutagenesis and genome editing (GE) driven by the Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR), maize mutational research is once again in the spotlight.

C-TERMINAL DOMAIN PHOSPHATASE-LIKE 3 contributes to GA-mediated growth and flowering by interaction with DELLA proteins.

Gibberellic acid (GA) plays a central role in many plant developmental processes and is crucial for crop improvement. DELLA proteins, the core suppressors in the GA signaling pathway, are degraded by GA via the 26S proteasomal pathway to release the GA response. However, little is known about the phosphorylation-mediated regulation of DELLA proteins.

Corrigendum: Proximal hyperspectral imaging detects diurnal and drought-induced changes in maize physiology.

[This corrects the article DOI: 10.3389/fpls.2021.

Chromatin attachment to the nuclear matrix represses hypocotyl elongation in Arabidopsis thaliana.

The nuclear matrix is a nuclear compartment that has diverse functions in chromatin regulation and transcription. However, how this structure influences epigenetic modifications and gene expression in plants is largely unknown. In this study, we show that a nuclear matrix binding protein, AHL22, together with the two transcriptional repressors FRS7 and FRS12, regulates hypocotyl elongation by suppressing the expression of a group of genes known as SMALL AUXIN UP RNAs (SAURs) in Arabidopsis thaliana.

Leaf growth - complex regulation of a seemingly simple process.

Understanding the underlying mechanisms of plant development is crucial to successfully steer or manipulate plant growth in a targeted manner. Leaves, the primary sites of photosynthesis, are vital organs for many plant species, and leaf growth is controlled by a tight temporal and spatial regulatory network. In this review, we focus on the genetic networks governing leaf cell proliferation, one major contributor to final leaf size.

Monitoring of drought stress and transpiration rate using proximal thermal and hyperspectral imaging in an indoor automated plant phenotyping platform.

Background: Thermography is a popular tool to assess plant water-use behavior, as plant temperature is influenced by transpiration rate, and is commonly used in field experiments to detect plant water deficit. Its application in indoor automated phenotyping platforms is still limited and mainly focuses on differences in plant temperature between genotypes or treatments, instead of estimating stomatal conductance or transpiration rate. In this study, the transferability of commonly used thermography analysis protocols from the field to greenhouse phenotyping platforms was evaluated.

EU legal proposal for genome-edited crops hints at a science-based approach.

The European Commission (EC) recently published a legislative proposal that hints at a science-based approach to the regulation of genome-editing applications in crops in the EU. This would be in line with legislation in an increasing number of countries worldwide, but further science-based advice on implementation will be essential.

SIAMESE-RELATED1 imposes differentiation of stomatal lineage ground cells into pavement cells.

The leaf epidermis represents a multifunctional tissue consisting of trichomes, pavement cells and stomata, the specialized cellular pores of the leaf. Pavement cells and stomata both originate from regulated divisions of stomatal lineage ground cells (SLGCs), but whereas the ontogeny of the stomata is well characterized, the genetic pathways activating pavement cell differentiation remain relatively unexplored. Here, we reveal that the cell cycle inhibitor SIAMESE-RELATED1 (SMR1) is essential for timely differentiation of SLGCs into pavement cells by terminating SLGC self-renewal potency, which depends on CYCLIN A proteins and CYCLIN-DEPENDENT KINASE B1.

Combining multiplex gene editing and doubled haploid technology in maize.

A major advantage of using CRISPR/Cas9 for gene editing is multiplexing, that is, the simultaneous targeting of many genes. However, primary transformants typically contain hetero-allelic mutations or are genetic mosaic, while genetically stable lines that are homozygous are desired for functional analysis. Currently, a dedicated and labor-intensive effort is required to obtain such higher-order mutants through several generations of genetic crosses and genotyping.

PhenoWell®-A novel screening system for soil-grown plants.

As agricultural production is reaching its limits regarding outputs and land use, the need to further improve crop yield is greater than ever. The limited translatability from in vitro lab results into more natural growth conditions in soil remains problematic. Although considerable progress has been made in developing soil-growth assays to tackle this bottleneck, the majority of these assays use pots or whole trays, making them not only space- and resource-intensive, but also hampering the individual treatment of plants.

Predicting yield of individual field-grown rapeseed plants from rosette-stage leaf gene expression.

In the plant sciences, results of laboratory studies often do not translate well to the field. To help close this lab-field gap, we developed a strategy for studying the wiring of plant traits directly in the field, based on molecular profiling and phenotyping of individual plants. Here, we use this single-plant omics strategy on winter-type Brassica napus (rapeseed).

Non-specific effects of the CINNAMATE-4-HYDROXYLASE inhibitor piperonylic acid.

Chemical inhibitors are often implemented for the functional characterization of genes to overcome the limitations associated with genetic approaches. Although it is well established that the specificity of the compound is key to success of a pharmacological approach, off-target effects are often overlooked or simply neglected in a complex biological setting. Here we illustrate the cause and implications of such secondary effects by focusing on piperonylic acid (PA), an inhibitor of CINNAMATE-4-HYDROXYLASE (C4H) that is frequently used to investigate the involvement of lignin during plant growth and development.

Improving crop yield potential: Underlying biological processes and future prospects.

The growing world population and global increases in the standard of living both result in an increasing demand for food, feed and other plant-derived products. In the coming years, plant-based research will be among the major drivers ensuring food security and the expansion of the bio-based economy. Crop productivity is determined by several factors, including the available physical and agricultural resources, crop management, and the resource use efficiency, quality and intrinsic yield potential of the chosen crop.

Opposing effects of - and -cinnamic acid during rice coleoptile elongation.

The phenylpropanoid cinnamic acid (CA) is a plant metabolite that can occur under a - or -form. In contrast to the proven bioactivity of the -form (-CA), the activity of -CA (-CA) is still a matter of debate. We tested both compounds using a submerged rice coleoptile assay and demonstrated that they have opposite effects on cell elongation.

IMPLANT: a new technique for transgene copy number estimation in plants using a single end-point PCR reaction.

Background: Copy number determination is one of the first steps in the characterization of transgenic plant lines. The classical approach to this, Southern blotting, is time-consuming, expensive and requires massive amounts of high-quality genomic DNA. Other PCR-based techniques are either inaccurate, laborious, or expensive.

BREEDIT: a multiplex genome editing strategy to improve complex quantitative traits in maize.

Ensuring food security for an ever-growing global population while adapting to climate change is the main challenge for agriculture in the 21st century. Although new technologies are being applied to tackle this problem, we are approaching a plateau in crop improvement using conventional breeding. Recent advances in CRISPR/Cas9-mediated gene engineering have paved the way to accelerate plant breeding to meet this increasing demand.

Identification of growth regulators using cross-species network analysis in plants.

With the need to increase plant productivity, one of the challenges plant scientists are facing is to identify genes that play a role in beneficial plant traits. Moreover, even when such genes are found, it is generally not trivial to transfer this knowledge about gene function across species to identify functional orthologs. Here, we focused on the leaf to study plant growth.

The translatability of genetic networks from model to crop species: lessons from the past and perspectives for the future.

Comparative analyses of growth-regulatory mechanisms between Arabidopsis and maize revealed that even when the gene space is conserved, the translation of knowledge from model species to crops is not trivial. Based on these insights, we formulate future opportunities to improve the interpretation of curiosity-driven research towards crop improvement.

Modulation of the DA1 pathway in maize shows that translatability of information from Arabidopsis to crops is complex.

Modern agriculture is struggling to meet the increasing food, silage and raw material demands due to the rapid growth of population and climate change. In Arabidopsis, DA1 and DAR1 are proteases that negatively regulate cell proliferation and control organ size. DA1 and DAR1 are activated by ubiquitination catalyzed by the E3 ligase BIG BROTHER (BB).

Interactive database of genome editing applications in crops and future policy making in the European Union.

European R&D in plant breeding is lagging behind, bound by strict genetically modified organism (GMO) regulations, applied to all crop varieties obtained with genome editing techniques. We developed an online database of worldwide genome editing applications in crops to support conclusions and to facilitate science-based policy making for this plant breeding innovation.

Optimized Transformation and Gene Editing of the B104 Public Maize Inbred by Improved Tissue Culture and Use of Morphogenic Regulators.

Plant transformation is a bottleneck for the application of gene editing in plants. In (maize), a breakthrough was made using co-transformation of the morphogenic transcription factors BABY BOOM (BBM) and WUSCHEL (WUS) to induce somatic embryogenesis. Together with adapted tissue culture media, this was shown to increase transformation efficiency significantly.

The heat is on: a simple method to increase genome editing efficiency in plants.

Background: Precision genome mutagenesis using CRISPR/Cas has become the standard method to generate mutant plant lines. Several improvements have been made to increase mutagenesis efficiency, either through vector optimisation or the application of heat stress.

Results: Here, we present a simplified heat stress assay that can be completed in six days using commonly-available laboratory equipment.