Editorial Overview : Growth and development

Non peer reviewe

A core mechanism for specifying root vascular patterning can replicate the anatomical variation seen in diverse plant species

Pattern formation is typically controlled through the interaction between molecular signals within a given tissue. During early embryonic development, roots of the model plant Arabidopsis thatiana have a radially symmetric pattern, but a heterogeneous input of the hormone auxin from the two cotyledons forces the vascular cylinder to develop a diarch pattern with two xylem poles. Molecular analyses and mathematical approaches have uncovered the regulatory circuit that propagates this initial auxin signal into a stable cellular pattern. The diarch pattern seen in Arabidopsis is relatively uncommon among flowering plants, with most species having between three and eight xylem poles. Here, we have used multiscale mathematical modelling to demonstrate that this regulatory module does not require a heterogeneous auxin input to specify the vascular pattern. Instead, the pattern can emerge dynamically, with its final form dependent upon spatial constraints and growth. The predictions of our simulations compare to experimental observations of xylem pole number across a range of species, as well as in transgenic systems in Arabidopsis in which we manipulate the size of the vascular cylinder. By considering the spatial constraints, our model is able to explain much of the diversity seen in different flowering plant species.Peer reviewe

Ectopic callose deposition into woody biomass modulates the nano-architecture of macrofibrils

Plant biomass plays an increasingly important role in the circular bioeconomy, replacing non-renewable fossil resources. Genetic engineering of this lignocellulosic biomass could benefit biorefinery transformation chains by lowering economic and technological barriers to industrial processing. However, previous efforts have mostly targeted the major constituents of woody biomass: cellulose, hemicellulose and lignin. Here we report the engineering of wood structure through the introduction of callose, a polysaccharide novel to most secondary cell walls. Our multiscale analysis of genetically engineered poplar trees shows that callose deposition modulates cell wall porosity, water and lignin contents and increases the lignin-cellulose distance, ultimately resulting in substantially decreased biomass recalcitrance. We provide a model of the wood cell wall nano-architecture engineered to accommodate the hydrated callose inclusions. Ectopic polymer introduction into biomass manifests in new physico-chemical properties and offers new avenues when considering lignocellulose engineering.Bourdon et al. demonstrate the possibility to ectopically synthesize callose, a polymer restricted to primary cell walls, into Arabidopsis and aspen secondary cell walls to manipulate their ultrastructure and ultimately reduce their recalcitrance

From procambium patterning to cambium activation and maintenance in the Arabidopsis root

In addition to primary growth, which elongates the plant body, many plant species also undergo secondary growth to thicken their body. During primary vascular development, a subset of the vascular cells, called procambium and pericycle, remain undifferentiated to later gain vascular cambium and cork cambium identity, respectively. These two cambia are the lateral meristems providing secondary growth. The vascular cambium produces secondary xylem and phloem, which give plants mechanical support and transport capacity. Cork cambium produces a protective layer called cork. In this review, we focus on recent advances in understanding the formation of procambium and its gradual maturation to active cambium in the Arabidopsis thaliana root.Peer reviewe

Phloem-transported cytokinin regulates polar auxin transport and maintains vascular pattern in the root meristem

Cytokinin phytohormones regulate a variety of developmental processes in the root such as meristem size, vascular pattern, and root architecture [1, 2 and 3]. Long-distance transport of cytokinin is supported by the discovery of cytokinins in xylem and phloem sap [4] and by grafting experiments between wild-type and cytokinin biosynthesis mutants [5]. Acropetal transport of cytokinin (toward the shoot apex) has also been implicated in the control of shoot branching [6]. However, neither the mode of transport nor a developmental role has been shown for basipetal transport of cytokinin (toward the root apex). In this paper, we combine the use of a new technology that blocks symplastic connections in the phloem with a novel approach to visualize radiolabeled hormones in planta to examine the basipetal transport of cytokinin. We show that this occurs through symplastic connections in the phloem. The reduction of cytokinin levels in the phloem leads to a destabilization of the root vascular pattern in a manner similar to mutants affected in auxin transport or cytokinin signaling [7]. Together, our results demonstrate a role for long-distance basipetal transport of cytokinin in controlling polar auxin transport and maintaining the vascular pattern in the root meristem

A PLETHORA-auxin transcription module controls cell division plane rotation through MAP65 and CLASP [Retracted article. See vol. 155, pg. 1189, 2013]

Our paper reported that Arabidopsis PLETHORA transcription factors regulate cell division planes by transcriptional activation of MAP65, which interacts with the CLASP protein to guide microtubule orientation. We recently identified mistakes affecting Figures 4N, S4B, and S6E in which original data were processed inappropriately such that the panels do not accurately report the original data. At least in one case, the original data did not support the figure’s conclusion. We believe that the most responsible course of action is to retract the paper. We sincerely apologize to the scientific community for any inconvenience that this might cause

Research data supporting “Ectopic callose deposition into woody biomass modulates the nano-architecture of macrofibrils”

The repository is divided in distinct folders which contain the raw data necessary to produce each figure of the “Ectopic callose deposition into woody biomass modulates the nano-architecture of macrofibrils” manuscript. As such, each folder is named after the figure it is referring to, and often contains several subfolders distinguishing the different data sets necessary to produce each figure. Each subfolder name ends up with the initials of the main co-author(s) originating the data they contain. See the 'Repository_readme' file for a detailed description of this dataseto The UK High-Field Solid-State NMR Facility used in this research was funded by EPSRC and BBSRC (EP/T015063/1) as well as the University of Warwick including via part funding through Birmingham Science City Advanced Materials Projects 1 and 2 supported by Advantage West Midlands (AWM) and the European Regional Development Fund (ERDF). We thank the Cambridge Advanced Imaging Center (CAIC) for providing access to their TEM resources and for technical assistance in imaging. The lignin analysis was supported by the Soluserre funding (Région Pays de la Loire, France). The authors acknowledge the funding received from the New Zealand Ministry of Business, Innovation, and Employment (MBIE) Strategic Science Investment Fund (Contract No. C0X41703, High-Value Biorefineries Portfolio) for supporting this work. FV acknowledges support from the Swedish Research Council (grants 621-2014-5295 and 2020-04720) and from the Knut and Alice Wallenberg Foundation (through the Wallenberg Wood Science Centre). Work in the YBA lab is supported by the Leverhulme Trust (Grant RPG-2016-136) which funded S.A. and C.P. and the UKRI Future Leader Fellowship program (MR/T04263X/1). Work in the JJL lab is supported by a grant from the National Science Centre Poland awarded to JJL as part of the SONATINA 3 programme (project number 2019/32/C/NZ3/00392) and a grant from National Science Centre Poland awarded as part of SONATA 17 programme (project number 2021/43/D/NZ9/01978). MB was supported by the ERC Proof of Concept APPLICAL (2020-2022) and the HiLife Proof of Concept APPLICAL (2020-2021) grants. L.K. received funding from the SNSF (P2LAP3_178062) and a Marie Curie IEF (No. 795250). Work in the YH lab was supported by the Finnish CoE in Molecular Biology of Primary Producers (Academy of Finland CoE programme 2014–2019) decision n°. 271832, the Gatsby Foundation (GAT3395/PR3), the University of Helsinki (award 799992091) and the ERC Advanced Investigator Grant SYMDEV (No. 323052)

Genome sequencing and population genomic analyses provide insights into the adaptive landscape of silver birch

Silver birch (Betula pendula) is a pioneer boreal tree that can be induced to flower within 1 year. Its rapid life cycle, small (440-Mb) genome, and advanced germplasm resources make birch an attractive model for forest biotechnology. We assembled and chromosomally anchored the nuclear genome of an inbred B. pendula individual. Gene duplicates from the paleohexaploid event were enriched for transcriptional regulation, whereas tandem duplicates were overrepresented by environmental responses. Population resequencing of 80 individuals showed effective population size crashes at major points of climatic upheaval. Selective sweeps were enriched among polyploid duplicates encoding key developmental and physiological triggering functions, suggesting that local adaptation has tuned the timing of and cross-talk between fundamental plant processes. Variation around the tightly-linked light response genes PHYC and FRS10 correlated with latitude and longitude and temperature, and with precipitation for PHYC. Similar associations characterized the growth-promoting cytokinin response regulator ARR1, and the wood development genes KAK and MED5A