It is reported that NtProRP1, an extracellular protein, localizes to the cell wall immediately after fertilization in Nicotiana tabacum, uncovering a new mechanism for NtProRP1 in regulating early embryogenesis and delivering a unique transcriptomic resource that advances understanding of extracellular signaling in plant embryogenesis.
Abstract
The plant extracellular space, including the cell wall, is a dynamic signaling compartment outside the plasma membrane that plays crucial roles in cell-cell communication and developmental coordination. Although early embryogenesis is known to be orchestrated by both intracellular and extracellular cues, the molecular mechanisms underlying extracellular regulation remain largely unexplored. Here, we report that NtProRP1, an extracellular protein, localizes to the cell wall immediately after fertilization in Nicotiana tabacum. Targeted knockout of NtProRP1 using the CRISPR-Cas9 system resulted in arrested embryos with irregular cell shapes and aberrant division patterns in aborted seeds. Furthermore, we performed high-resolution transcriptome profiling on a limited number of isolated two-celled proembryos from wild-type (WT) and Ntprorp1 plants, enabling the detection of early transcriptional changes with minimal interference from surrounding tissues. Genes involved in the synthesis and modification of cell wall components, including cellulose, hemicellulose, and pectin, were coordinately upregulated at the onset of embryogenesis in the Ntprorp1 mutant. Further analysis suggests a possible role for NtProRP1 in cell wall formation via the cell wall integrity (CWI) maintenance mechanism, potentially through the involvement of components such as receptor-like kinases (RLKs), mitogen-activated protein kinases (MAPKs), Ca2+ flux, and multiple phytohormones. Together, these results uncover a new mechanism for NtProRP1 in regulating early embryogenesis and deliver a unique transcriptomic resource that advances understanding of extracellular signaling in plant embryogenesis.
The cell wall integrity (CWI) pathway is triggered by plasma membrane-localized receptors in plant cells and serves to orchestrate responses to cell wall damage by initiating compensatory changes under stressful environments. The essential role of CWI maintenance as part of plants' interactions with pests or pathogens and during growth is well known. Nevertheless, CWI pathways remain to be fully characterized. Here, we show that altered Integrin-Linked Kinase 1 (ILK1) expression causes widespread defects in the transcriptional program activated by the bacterial elicitor flg22, primarily in genes associated with cell wall integrity and immunity. These transcriptional deficiencies are recapitulated in mutant lines with altered ILK4 or ILK5 expression. Analysis of molecular and cellular defenses in ilk mutants revealed reduced callose accumulation in leaves treated with bacterial (elf18) and plant (pep1) elicitors and increased pathogen susceptibility. Histochemical analysis of cell-wall-associated staining across diverse cells and organs of ilk mutants revealed modified lignin-associated patterns in the root xylem and altered calcofluor staining patterns in the seed coat. All ilk mutants exhibited altered root morphology due to mechano-touch and high-NaCl stress. Based on these results, we propose that ILKs contribute to pathways connecting elicitor-triggered immune signaling with cell-wall-associated stress responses and that ILK-related defense functions may extend to the cotton root-nematode interaction, while the mechanism remains to be elucidated.
Gizem Dimlioglu, N. Nejat, Emily G Cooley et al.· Plant Science· 0 citations
Programmed cell death (PCD) is a fundamental and tightly regulated process that shapes plant development and ensures adaptive responses to environmental stimuli. This review provides an integrative overview of developmental PCD (dPCD) across vegetative and generative stages, from reproductive development and embryogenesis to vascular differentiation, aerenchyma formation, organ shaping, senescence, and abscission. We summarize current knowledge of the molecular, cellular, and physiological mechanisms governing dPCD, highlighting the coordinated roles of transcription factors, caspase-like proteases, reactive oxygen species, calcium signalling or phytohormones. The review further integrates insights from systematic embryology to illustrate how dPCD contributes to the diversity and stability of developmental patterns. Recent advances in omics technologies, single-cell analyses, live-cell imaging, and genome-editing tools are accelerating the identification of novel regulatory pathways and highlighting previously unrecognized layers of PCD control. Understanding developmental PCD is therefore essential not only for revealing the fundamental principles that govern plant growth and tissue patterning but also for enabling targeted manipulation of cell death pathways, with direct implications for crop improvement, stress resilience, and sustainable agriculture.
Jacek Łuc, M. Kwiatkowska, A. Słomka et al.· Journal of Experimental Bota...· 0 citations
The shoot apical meristem (SAM) serves as the cellular source of aboveground plant development and is precisely regulated by a complex interplay of genetic, hormonal, and environmental factors. Central to this regulation is the CLAVATA3 (CLV3)–WUSCHEL (WUS) negative feedback loop, which maintains SAM homeostasis by balancing stem cell proliferation and differentiation. Among the diverse regulatory mechanisms, reversible protein phosphorylation, which is mediated by protein kinases and phosphatases, has emerged as a key posttranslational modification that integrates internal and external signals to modulate SAM activity. This review summarizes recent advances in understanding the roles of kinases and phosphatases in SAM maintenance, with a particular focus on phosphorylation-mediated control of the CLV3–WUS pathway and associated signaling networks. By synthesizing these molecular insights, we aim to provide a comprehensive reference for deciphering the regulatory mechanisms underlying SAM homeostasis. A deeper understanding of SAM regulation not only advances fundamental knowledge of plant developmental biology but also holds significant potential for improving crop architecture and agricultural productivity.
The plant cytoskeleton undergoes extensive remodelling during the formation of Meloidogyne incognita-induced giant cells and plays a crucial role in their ontogenesis. Fimbrins (FIMs) are a conserved family of actin-bundling proteins that regulate cytoskeletal architecture and dynamics during diverse cellular processes. However, their functional contribution to giant cell development remains unknown. Here, we show that all five Arabidopsis thaliana FIM genes (FIM1-FIM5) are expressed in M. incognita-induced galls, with expression levels declining as giant cells mature. Loss of function of FIM2 or FIM3, as well as FIM2 overexpression, altered actin organisation and giant cell morphology, resulting in reduced cytoplasmic density and cell wall stubs. These defects were associated with changes in cell wall composition and vacuolar organisation. FIM2 overexpression increased the accumulation of low-methyl-esterified homogalacturonan in giant cell walls, whereas fim2 and fim3 mutants showed reduced accumulation, consistent with altered cell wall thickness. Increased vacuolar sizes in INT1-eGFP Arabidopsis galls following latrunculin B treatment further indicates that actin organisation is required to maintain vacuolar architecture in giant cells. Moreover, fim2, fim3 and FIM2OE lines showed enhanced resistance to M. incognita, with reduced gall formation and egg mass production. Together, our findings identify FIM2 and FIM3 as critical regulators of actin organisation, cell wall remodelling and vacuolar architecture during gall development, highlighting the importance of a balanced cytoskeleton dynamics for successful nematode parasitism.
D. H. Pinheiro, Hannie van der Honing, La Hoang Anh et al.· Plant, Cell and Environment· 0 citations
While cell identities are established early during embryogenesis, these cells remain immature until germination, and the mechanisms enforcing this developmental pause are poorly understood. Embryonic stomatal cells provide a model to study this pause as the stomatal transcription factor FAMA, normally sufficient for Guard Cell maturation in seedlings, can not drive maturation in the Arabidopsis embryo. Here we show that FAMA’s ability to drive maturation depends on leaf polarity and adaxial stomatal cells can progress further in their lineage. We next find that ERECTA-family receptor signaling, which controls stomatal patterning, also suppresses embryonic stomatal maturation. In er erl1 erl2 mutants, cell pairs at the cotyledon tip acquire characteristics of maturing guard cells: cell wall reinforcement, pore-associated thickening, and expression of late lineage markers as identified by whole embryo transcriptomics. This precocious maturation however remains incomplete: many GC markers remain absent, and cells lack an open pore and mature vacuoles. Genetic analysis shows that partial maturation requires but is not limited by low levels of FAMA. Restriction of maturation to the cotyledon tip correlates with locally elevated ERECTA-family receptor abundance, while high auxin appears dispensable for this. Finally, we show that EPFL-ER signaling mediates leaf tip Guard Cell size postembryonically as well. Altogether, we identify ERECTA signaling as a local brake on embryonic stomatal cell maturation, discovering another way to push precocious stomatal cell maturation that results in a complex, partially mature cell state that provide insights into the limitations on cell embryonic cell maturation.
Yadhusankar Sasidharan, Vijay Suryavanshi, Pablo González-Suárez et al.· bioRxiv· 0 citations
CLAVATA3 (CLV3) has long been thought to be a negative regulator in control of WUSCHEL (WUS) expression domain, whereas cytokinin signaling increases WUS expression at the transcriptional level. Whether these two important pathways on WUS regulation are coordinated in stem cell niche is unknown. Here, we show that CLV signaling has a dual-directional effect on WUS by limiting its expression domain but maintaining its expression level. CLV1 phosphorylates the transcription factor BRASSINAZOLE RESISTANT 1 (BZR1) to release the inhibitory effect of BZR1 on cytokinin biosynthesis, which relays the CLV signal to maintain WUS expression levels in individual cells. Upon heat stress, decreased CLV signaling enhances the stability of BZR1 in the nucleus to repress cytokinin biosynthesis and WUS content to protect stem cells from heat shock. Our results revealed a positive feedback loop between CLV3 and WUS that is mediated by multiple hormone interactions, which are critical for plants to adapt to harsh environments.
Mengchu Xu, Haijun Wu, Chengwu Liu et al.· Molecular Plant· 0 citations