Biology subjects

Ripper, D.

Publications and source records attributed to Ripper, D..

5 recordsLinked to original sources

bioRxiv2024

An AINTEGUMENTA phospho-switch controls bilateral stem cell activity during secondary growth

Plant stem cells have the remarkable ability to give rise to distinct tissues and organs throughout development. Two concentric cylinders of actively dividing stem cells are the main drivers of radial thickening during secondary growth, each producing distinct vascular cell types towards the inside and the outside. While the molecular mechanisms underlying their initiation have been well studied, it remains unclear how these stem cell layers determine which cell type is generated. Here, we demonstrate that the cross-talk between the ERECTA (ER) receptor pathway and auxin signalling controls the amount and choice of output tissue in these two stem cell regions. Mechanistically, we show that the ER pathway phosphorylates the transcription factor AINTEGUMENTA, thereby modulating bilateral stem cell activity and favouring the differentiation of only one type of cell. Our results thus show that the phosphorylation status of ANT regulates root girth and biomass accumulation by influencing bilateral stem cell production. This highlights the critical role of post-translational modifications in plant growth and development. SignificanceThis study uncovers a critical regulatory mechanism governing bilateral stem cell activity during plant radial growth. Stem cells in the cambia proliferate and differentiate into specialized tissues like wood and cork, key sites of biomass accumulation. By exploring the interplay between the ERECTA (ER) receptor and auxin signalling, we reveal how these pathways modulate stem cell differentiation and radial thickening through the phosphorylation of the transcription factor AINTEGUMENTA (ANT). Phosphorylation status of ANT modulates stem cell activity, dictating the production of specific vascular cell types like wood thus controlling root girth. This research underscores the importance of post-translational modifications in plant development and provides a novel regulation underpinning stem cell differentiation, with significant implications for enhancing biomass accumulation as wood.

plant biology↗

bioRxiv2024

MYB68 orchestrates cork differentiation by regulating stem cell proliferation and suberin deposition

Plants have developed specialized barriers to protect and isolate the inner tissues from the environment while maintaining homeostasis. Different barriers are present in various organs and at different growth stages. During secondary growth, the periderm acts as the protective tissue, covering roots, stems, and branches as they become thick. The periderm is a dynamic barrier comprising a stem cell niche known as the cork cambium, which bifacially divides to generate the phelloderm inward and the cork outward. Cork cells have a unique cell wall impregnated with suberin and lignin polymers, essential for the barrier function. Despite its importance, the differentiation process that forms new cork cells from the stem cell is largely unknown. In this work, we identify members of the MYB36-subclade transcription factors as key regulators of cork differentiation. On the one hand, this set of transcription factors promotes suberin deposition by inducing the expression of enzymes involved in all steps of suberin biosynthesis, including the recently discovered suberin-polymerizing enzymes GDS Lipases; on the other hand, it represses cork cambium proliferation. Furthermore, we demonstrated that suberin deposition in the cork is a robust process regulated by a complex network of transcription factors, including other MYB transcription factors that activate suberin deposition in the endodermis. However, only members of the MYB36 subclade can repress cell proliferation in different developmental contexts, highlighting general and specific functions for MYB transcription factors. These findings have broad applicability, as tissue-specific manipulation of MYB activity has the potential for improving traits of biotechnological interest, such as thicker periderms and more suberized cork layers, and for assessing how these traits affect plant performance in response to stresses.

plant biology↗

bioRxiv2022

bHLH heterodimer complex variations shape meristems in Arabidopsis thaliana by affecting target gene specificity

The main regions of cell proliferation in plants are the root and shoot apical meristems during primary growth and the vascular cambia as lateral meristems during secondary thickening. A number of unique regulators have been described in each of these meristems, suggesting that these different meristems might have independently evolved dedicated transcriptional networks to balance cell proliferation. Here, we show that the basic Helix Loop Helix (bHLH) transcription factor complexes formed by TARGET OF MONOPTEROS5 (TMO5), LONESOME HIGHWAY (LHW) and their close homologs are broadly expressed throughout plant development and operate as general regulators of cell proliferation in all meristems. Yet, genetic and expression analyses indicate that these complexes have specific functions in distinct meristems mediated by heterodimer complex variations between members of the TMO5 and LHW subclades. We determine that this is primarily due to their expression domains limiting the possible combinations of heterodimer complexes within a certain meristem, and to a certain extent to the absence of some members in a given meristem. We further demonstrate target gene specificity for heterodimer complexes, suggesting that spatial differences in transcriptional responses through heterodimer diversification allow a common bHLH heterodimer complex module to contribute to the control of cell proliferation in multiple meristems.

developmental biology↗

bioRxiv2021

ABA homeostasis and long-distance translocation is redundantly regulated by ABCG ABA importers

The effects of abscisic acid (ABA) on plant growth, development and response to the environment depend on local ABA concentrations. Here, we exploited a genome-scale amiRNA screen, targeting the Arabidopsis transportome, to show that ABA homeostasis is regulated by two previously unknown ABA transporters. ABCG17 and ABCG18 are localized to the plasma membranes of leaf mesophyll and stem cortex cells to redundantly promote ABA import, leading to conjugated inactive ABA sinks, thus restricting stomatal closure. ABCG17 and ABCG18 double knockdown revealed that the transporters encoded by these genes not only limit stomatal aperture size, conductance and transpiration while increasing water-use efficiency but also control ABA translocation from the shoot to the root to regulate lateral root emergence. The proposed ABCG17- and ABCG18-dependent ABA glucosyl ester shoot sink mechanism is restrained under abiotic stress conditions to further activate the ABA responses.

plant biology↗

bioRxiv2020

AUXIN RESPONSE FACTOR 6 (ARF6) and ARF8 promote Gibberellin-mediated hypocotyl xylem expansion and cambium homeostasis

During secondary growth, the thickening of plant organs, wood (xylem) and bast (phloem) are continuously produced by the vascular cambium. In Arabidopsis hypocotyl and root, we can distinguish two phases of secondary growth based on cell morphology and production rate. The first phase, in which xylem and phloem are equally produced, precedes the xylem expansion phase in which xylem formation is enhanced and xylem fibers differentiate. It is known that Gibberellins (GA) trigger this developmental transition via the degradation of DELLA proteins and that the cambium master regulator BREVIPEDICELLUS/KNAT1 (BP/KNAT1) and the receptor like kinases ERECTA and ERL1 regulate this process downstream of GA. However, our understandings on the regulatory network underlying GA-mediated secondary growth, are still limited. Here, we demonstrate that DELLA-mediated xylem expansion is mainly achieved through RGA and GAI and that RGA and GAI promote cambium senescence. We further show that AUXIN RESPONSE FACTOR (ARF6) and ARF8, which physically interact with DELLAs, specifically repress phloem proliferation and induce cambium senescence during the xylem expansion phase. Moreover, the inactivation of BP in arf6 arf8 background revealed an essential role for ARF6 and ARF8 in cambium establishment and maintenance. Overall, our results shed light on a pivotal hormone cross-talk between GA and auxin in the context of plant secondary growth.

plant biology↗