Biology subjects

Domonkos, I.

Publications and source records attributed to Domonkos, I..

4 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↗

bioRxiv2024

Lipid polymorphism of the marginal region of plant thylakoid membranes

Thylakoid membranes (TMs) of oxygenic photosynthetic organisms are flat membrane vesicles, which form highly organized, interconnected membrane networks. In vascular plants, they are differentiated into stacked and unstacked regions, the grana and stroma lamellae, respectively; they are densely packed with protein complexes performing the light reactions of photosynthesis and generating a proton motive force (pmf). The maintenance of pmf and its utilizations for ATP synthesis require sealing the TMs at their highly curved regions (CRs). These regions are devoid of chlorophyll-containing proteins but contain the curvature inducing CURVATURE THYLAKOID1 (CURT1) proteins, and are enriched in lipids. Because of the highly curved nature of this region, at the margins of grana and stroma TMs, the molecular organization of lipid molecules is likely to possess distinct features compared to those in the major TM domains. To clarify this question, we isolated CR fractions from Spinacia oleracea and, using BN-PAGE and western blot analysis, verified that they are enriched in CURT1 proteins and in lipids. The lipid phase behavior of these fractions was fingerprinted with 31P-NMR spectroscopy, which revealed that the bulk lipid molecules assume a non-bilayer, isotropic lipid phase. This finding underpins the importance of the main, non-bilayer lipid species, monogalactosyldiacylglycerol, of TMs in their self-assembly and functional activity.

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↗

bioRxiv2021

Trimeric Photosystem I facilitates energy transfer from phycobilisomes in Synechocystis PCC 6803

In cyanobacteria, phycobilisomes serve as peripheral light-harvesting complexes of the two photosystems, extending their antenna size and the wavelength range of photons available for photosynthesis. The abundance of phycobilisomes, the number of phycobiliproteins they contain, and their light-harvesting function are dynamically adjusted in response to the physiological conditions. Phycobilisomes are also thought to be involved in state transitions that maintain the excitation balance between the two photosystems. Unlike its eukaryotic counterpart, PSI is trimeric in many cyanobacterial species and the physiological significance of this is not well understood. Here we compared the composition and light-harvesting function of phycobilisomes in cells of Synechocystis sp. PCC 6803, which has primarily trimeric PSI, and the{Delta} psaL mutant unable to form trimers. We also investigated a mutant additionally lacking the PsaJ and PsaF subunits of PSI. Both strains with monomeric PSI accumulated significantly more allophycocyanin per chlorophyll, indicating higher abundance of phycobilisomes. On the other hand, a higher phycocyanin:allophycocyanin ratio in WT suggests larger phycobilisomes or the presence of APC-less phycobilisomes (CpcL-type), that are not assembled in cells with monomeric PSI. Steady-state and time-resolved fluorescence spectroscopy at room temperature and 77 K revealed that PSII receives more energy from the phycobilisomes at the expense of PSI in cells with monomeric PSI, regardless of the presence of PsaF. Taken together, these results show that the oligomeric state of PSI has an impact on the excitation energy flow in Synechocystis. One-sentence summaryCyanobacterial mutants with monomeric PSI show changes in the composition and abundance of phycobilisomes and in the excitation energy transfer to PSII and PSI.

biophysics↗