Spatio-temporal imaging of cell fate dynamics in single plant cells using luminescence microscope

Debunking the idea of biological optimisation: quantitative biology to the rescue

The idea that plants would be efficient, frugal or optimised echoes the recurrent semantics of 'blueprint' and 'program' in molecular genetics. However, when analysing plants with quantitative approaches and systems thinking, we instead find that plants are the results of stochastic processes with many inefficiencies, incoherence or delays fuelling their robustness. If one had to highlight the main value of quantitative biology, this could be it: plants are robust systems because they are not efficient. Such systemic insights extend to the way we conduct plant research and opens plant science publication to a much broader framework.

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.

A non-cell-autonomous circadian rhythm of bioluminescence reporter activities in individual duckweed cells

The circadian clock is responsible for the temporal regulation of various physiological processes in plants. Individual cells contain a circadian oscillator consisting of a clock gene circuit that coordinates physiological rhythms within the plant body in an orderly manner. The coordination of time information has been studied from the perspective of cell-cell local coupling and long-distance communication between tissues based on the view that the behavior of circadian oscillators represents physiological rhythms. Here, we report the cellular circadian rhythm of bioluminescence reporters that are not governed by the clock gene circuit in expressing cells. We detected cellular bioluminescence rhythms with different free-running periods in the same cells using a dual-color bioluminescence monitoring system in duckweed (Lemna minor) transfected with Arabidopsis CIRCADIAN CLOCK ASSOCIATED 1::luciferace+ (AtCCA1::LUC+) and Cauliflower mosaic virus 35S::modified click-beetle red-color luciferase (CaMV35S::PtRLUC) reporters. Co-transfection experiments with the two reporters and a clock gene-overexpressing effector revealed that the AtCCA1::LUC+ rhythm, but not the CaMV35S::PtRLUC rhythm, was altered in cells with a dysfunctional clock gene circuit. This indicated that the AtCCA1::LUC+ rhythm is a direct output of the cellular circadian oscillator, whereas the CaMV35S::PtRLUC rhythm is not. After plasmolysis, the CaMV35S::PtRLUC rhythm disappeared, whereas the AtCCA1::LUC+ rhythm persisted. This suggests that the CaMV35S::PtRLUC bioluminescence has a symplast/apoplast-mediated circadian rhythm generated at the organismal level. The CaMV35S::PtRLUC-type bioluminescence rhythm was also observed when other bioluminescence reporters were expressed. These results reveal that the plant circadian system consists of both cell-autonomous and noncell-autonomous rhythms that are unaffected by cellular oscillators.

Molecular Mechanisms Underlying the Establishment and Maintenance of Vascular Stem Cells in Arabidopsis thaliana

The vascular system plays pivotal roles in transporting water and nutrients throughout the plant body. Primary vasculature is established as a continuous strand, which subsequently initiates secondary growth through cell division. Key factors regulating primary and secondary vascular developments have been identified in numerous studies, and the regulatory networks including these factors have been elucidated through omics-based approaches. However, the vascular system is composed of a variety of cells such as xylem and phloem cells, which are commonly generated from vascular stem cells. In addition, the vasculature is located deep inside the plant body, which makes it difficult to investigate the vascular development while distinguishing between vascular stem cells and developing xylem and phloem cells. Recent technical advances in the tissue-clearing method, RNA-seq analysis and tissue culture system overcome these problems by enabling the cell-type-specific analysis during vascular development, especially with a special focus on stem cells. In this review, we summarize the recent findings on the establishment and maintenance of vascular stem cells.