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Through a combination of experimental and computational approaches, the interplay between the plant hormone auxin and the auxin-induced PLETHORA transcription factors is shown to control zonation and gravity-prompted growth movements in plants.

In the version of this article initially published, there was a mistake in the calculation of the nucleotide mutation rate per site per generation: 1 × 10⁻⁹ mutations per site per generation was used, whereas 9.5 × 10⁻⁹ was correct. This error affects the interpretation of population-size changes over time and their possible correspondence with known geological events, as shown in the original Fig. 4 and supporting discussion in the text, as well as details in the Supplementary Note. Neither the data themselves nor any other results are affected. Figure 4 has been revised accordingly. Images of the original and corrected figure panels are shown in the correction notice.

The prolonged cold of winter is required for the flowering of many plants. Now the identification of a previously unknown long-term cold-sensing mechanism helps to reveal how plants are able to time their flowering correctly.

A study using Arabidopsis shows that plants can monitor the integrity of their outer barriers by sensing gas diffusion, enabling them to initiate wound repair to prevent water loss and pathogen entry.

Water-conducting tissues inside plant roots are surrounded by impermeable cells. This protective barrier is punctured by ‘passage cells’, which are thought to regulate nutrient uptake. How these cells form has now been revealed.

A combination of lineage tracing and single-cell RNA sequencing reveals how xylem and phloem parenchyma cells in the secondary tissue of Arabidopsis root mature gradually. Upon root barrier injury, this maturation involves a change in cell identity from phloem parenchyma to barrier cell types.

Victor Albert, Petri Auvinen, Ykä Helariutta, Jaakko Kangasjärvi and colleagues report the reference genome of the silver birch (Betula pendula) and resequencing of 150 birch individuals. They infer past population size crashes consistent with historical periods of climatic change and identify candidate targets of more recent positive selection.

The polar transport of the plant hormone auxin is dependent on the localization of its efflux carriers called PINs, but the mechanism mediating polarity of PIN proteins within cells remains unclear. This study suggests a two-step mechanism generating PIN polarity. PINs are first targeted to the plasma membrane in a non-polar manner, and polarity is established in subsequent step involving internalization and recycling. Interference with endocytosis results in the loss of PIN polarity leading to a perturbation in auxin gradients.

In many plants, only the outermost cells are specified into the epidermis, with underlying mechanisms unknown. Here, the authors show that a key epidermis identity gene is activated in surface cells, via positional cues involving mechanical signals.

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.

Auxin is a key regulator in vascular cambium development. This study shows that gibberellins promote polar auxin transport along the root, which leads to broadening of high auxin signalling domain in cambium, and thus, to increased xylem formation.

Genes encoding the class A auxin-response factor group of plant transcriptional activators reside in constitutively open chromatin, enabling their continual regulation by transcriptional repressors to modulate auxin signalling throughout development.

This study developed a user-friendly genome editing system that can efficiently conditionally knock out target genes in a temporally inducible and cell-type-specific manner.

Recent studies inArabidopsis thalianahave identified interconnected signalling networks that regulate plant vascular development. These findings have increased our understanding of vascular development from early cell specification during embryogenesis to the latest stages of differentiation of the phloem and xylem.

Radial growth in the roots of Arabidopsis, which is mediated by gene expression activated by the mobile PEAR1 and PEAR2 transcription factors, is initiated around protophloem-sieve-element cell files of procambial tissue.

In the roots of Arabidopsis thaliana, cells with xylem identity and high levels of auxin signalling function as organizer cells that direct neighbouring vascular cambial cells to act as stem cells.

The vascular cambium contains meristem cells that produce secondary xylem and phloem in the stems and roots of many plants. Its activity largely determines wood formation. Now, a genome-wide transcript profiling of Arabidopsis thaliana root cambium is presented to unlock the complex network that regulates cambium development and activity.