Biology subjects

Feher, A.

Publications and source records attributed to Feher, A..

5 recordsLinked to original sources

bioRxiv2026

Arabidopsis RETINOBLASTOMA-RELATED controls cell size during plant development in a dose-dependent manner

The RETINOBLASTOMA-RELATED (RBR) protein in plants functions as a cell-cycle inhibitor, regulating cell numbers in developing organs and establishing cellular quiescence during growth. Although the role of RBR counterparts in animals also involves regulating cell size, this potential function remains unexplored in plants. We investigated transgenic Arabidopsis plants with altered RBR levels and observed corresponding changes in cell size from embryogenesis through organ development. In addition, stomatal meristemoid cells with reduced RBR levels divided beyond the size threshold, whereas elevated RBR levels increased their size. RBR stimulated terminal differentiation in the stomatal lineage by inducing MUTE and CYCLIN D5;1 expression, whereas reduced RBR levels maintained asymmetric divisions through high SPEECHLESS and CYCLIN D3;1 expression. Interestingly, the cell proliferation-dependent phosphorylation of RBR at the conserved 911Ser site positively correlated with RBR protein levels in the transgenic lines and aligned with the effect of RBR on cell size. This study discusses the potential link between RBRs control of cell proliferation and cell size, providing new insights into the coordinated regulation of plant development.

plant biology↗

bioRxiv2026

Complex regulation of RETINOBLASTOMA-RELATED's interactions with E2Fs via phosphorylation

Arabidopsis RETINOBLASTOMA-RELATED (RBR) regulates cell proliferation by interacting with E2F transcription factors and DIMERIZATION PARTNER, RB-LIKE, E2F AND MULTI-VULVAL CLASS B COMPLEX (DREAM) components. Although CDK-CYCD phosphorylation is believed to affect RBRs E2F-binding capacity, the precise phosphorylation events inhibiting RBRs cell cycle function remain unclear. This study found RBR phosphorylated at 13 of 16 CDK sites in Arabidopsis, with many phosphorylated forms still binding E2Fs. In contrast, multi-phosphorylated RBR forms with phosphorylated 911S site in Arabidopsis thaliana and corresponding sites in Medicago truncatula or Brassica napus do not co-purify with E2Fs and DREAM components but interact with RNA-binding proteins involved in post-transcriptional regulation through ribosomal biogenesis and protein translation. The 911S phosphorylation is high in proliferating cells and rapidly diminishes under DNA damage conditions, indicating its role in switching from proliferation to quiescence under stress. However, molecular modelling implies that this site is not accessible for phosphorylation if RBR is in complex with E2Fs. These findings suggest that different phosphorylation events inhibit RBRs capacity to form complexes with E2Fs and to release E2Fs from RBR inhibition. We posit that multi-site phosphorylation coupled to 911S impedes free RBRs binding to E2Fs and DREAM components, but this is not the initial inhibitory phosphorylation contributing to the disruption of RBR-E2F-DP complexes. Rather, it facilitates RBR interaction with proteins involved in post-transcriptional cell cycle regulation.

plant biology↗

bioRxiv2024

Retinoblastoma-related (RBR) has both canonical and non-canonical regulatory functions during thermo-morphogenic responses in Arabidopsis seedlings

Warm temperatures accelerate plant growth, but the underlying molecular mechanism is not fully understood. Here, we show that increasing the temperature from 22{degrees}C to 28{degrees}C rapidly activates proliferation in the apical shoot and root meristems of wild-type Arabidopsis seedlings. We found that one of the central regulators of cell proliferation, the cell cycle inhibitor RETINOBLASTOMA-RELATED (RBR), is suppressed by warm temperatures. RBR became hyper-phosphorylated at a conserved CYCLIN-DEPENDENT KINASE (CDK) site in young seedlings growing at 28{degrees}C, in parallel with the stimulation of the expressions of the regulatory CYCLIN D/A subunits of CDK(s). Interestingly, while under warm temperatures ectopic RBR slowed down the acceleration of cell proliferation, it triggered elongation growth of post-mitotic cells in the hypocotyl. In agreement, the central regulatory genes of thermomorphogenic response, including PIF4 and PIF7, as well as their downstream auxin biosynthetic YUCCA genes (YUC1-2 and YUC8-9) were all up-regulated in the ectopic RBR expressing line but down-regulated in a mutant line with reduced RBR level. We suggest that RBR has both canonical and non-canonical functions under warm temperatures to control proliferative and elongation growth, respectively.

plant biology↗

bioRxiv2020

Posttranslational modification of the RHO of plants protein RACB by phosphorylation and cross-kingdom conserved ubiquitination

Small RHO-type G-proteins act as signaling hubs and master regulators of polarity in eukaryotic cells. Their activity is tightly controlled, as defective RHO signaling leads to aberrant growth and developmental defects. Two major processes regulate G-protein activity: canonical shuttling between different nucleotide bound states and posttranslational modification (PTM), of which the latter can support or suppress RHO signaling, depending on the individual PTM. In plants, regulation of Rho of plants (ROPs) signaling activity has been shown to act through nucleotide exchange and GTP hydrolysis, as well as through lipid modification, but there is little data available on phosphorylation or ubiquitination of ROPs. Hence, we applied proteomic analyses to identify PTMs of the barley ROP RACB. We observed in vitro phosphorylation by barley ROP binding kinase 1 and in vivo ubiquitination of RACB. Comparative analyses of the newly identified RACB phosphosites and human RHO protein phosphosites revealed conservation of modified amino acid residues, but no overlap of actual phosphorylation patterns. However, the identified RACB ubiquitination site is conserved in all ROPs from Hordeum vulgare, Arabidopsis thaliana and Oryza sativa and in mammalian Rac1 and Rac3. Point mutation of this ubiquitination site leads to stabilization of RACB. Hence, this highly conserved lysine residue may regulate protein stability across different kingdoms.

plant biology↗

bioRxiv2019

Two Receptor-Like Kinases Required For Arabidopsis Endodermal Root Organisation Shape The Rhizosphere Microbiome

The Casparian Strip (CS) constitutes a physical diffusion barrier to water and nutrients in plant roots, and is formed by the polar deposition of lignin polymer in the endodermis. This precise pattern of lignin deposition is thought to be mediated by the scaffolding activity of membrane-bound Casparian Strip domain proteins (CASPs). However, we show that endodermis-specific receptor-like kinase 1 (ERK1) and ROP Binding Kinase1 (RBK1) are also involved in this intricate process, with the former playing an essential role both in the localization of CASP1 and in lignin deposition. We further characterised ERK1 and determined its subcellular localisation in the cytoplasm and nucleus of the endodermis, as well as provide evidence for its involvement in a signalling pathway together with the circadian clock regulator, Time for Coffee (TIC). We also show that disruption to CS organisation and increased suberisation in the endodermis due to loss of function of either ERK1 or TIC collectively leads to an altered root microbiome composition. Thus, our work reveals additional players in the complex cascade of signalling events operating in the root endodermis to establish both the CS diffusion barrier and the microbial composition of the rhizosphere.

plant biology↗