Biology subjects

Bar-Zvi, D.

Publications and source records attributed to Bar-Zvi, D..

8 recordsLinked to original sources

bioRxiv2025

Ubiquitin ligase PUB41 modulates root hair development in Arabidopsis via interaction with the auxin polar transporter PIN2

Root hairs are short-lived, elongated tubular extensions of epidermal cells, that increase the surface area improving absorption of water and nutrients. Root hair development is affected by developmental, environmental, and hormonal cues, primarily Auxin. Auxin is synthesized in shoot and root apical transporters. Here, we report that mutants of the Arabidopsis PLANT U-BOX41 (AtPUB41) gene encoding a ubiquitin ligase (E3) develop fewer and shorter root hairs than wild-type (WT) plants. pub41 mutants are not impaired in sensing and responding to exogenous auxin, suggesting that the root hair phenotype may result from a change in auxin levels and/or distribution. Indeed, Auxin enhances the steady-state levels of PUB41 transcript and protein in the roots. A catalytically inactive decoy protein lacking the U-box, PUB41({Delta}U), complements the sparse root hair phenotype of pub41 mutants to the same extent as full-length PUB41. Plants expressing PUB41({Delta}U) are hyperresponsive to auxin-induced root hair development and PUB41({Delta}U) accumulates in the root elongation and differentiation zones, preferentially in trichoblast cells and their root hairs. Furthermore, in these cells, PUB41-eGFP and PUB41({Delta}U)-eGFP are primarily located on the anticlinal faces, as is the auxin PIN2 exporter. We show colocalization of PUB41({Delta}U)-eGFP and PIN2-mCherry, and binding in vitro of PUB41 to the cytoplasmic hydrophilic loop of PIN2. Moreover, PUB41({Delta}U) protein stabilizes PIN2 and enhances its abundance in the roots. Our results indicate that PUB41 modulates root hair development via interaction with PIN2. Significance StatementRoot hairs are extensions of the root epidermal cells, which are crucial for the uptake of water and nutrients from the soil. Root hair development is highly regulated and affected by developmental, environmental, and hormonal cues. In this study, we demonstrate that the auxin-induced ubiquitin ligase, PLANT U-BOX 41 (PUB41), regulates root-hair development by interacting with the auxin polar transporter PIN2 responsible for determining auxin levels.

plant biology↗

bioRxiv2024

Arabidopsis ubiquitin ligase PUB41 is a positive regulator of the ABA response

Seed germination is a highly controlled developmental process. Prevention of early germination is essential to avoid germination at a time that is not likely to allow the completion of the plant life cycle before entering unfavorable seasons. The plant hormone ABA is the key regulator of seed dormancy and inhibition of germination. ABA is also involved in the plant response to drought. Here we report on the involvement of AtPUB41, a U-BOX E3 ubiquitin ligase from Arabidopsis thaliana, in regulating ABA signaling, seed dormancy, germination, and drought resilience. AtPUB41 is expressed in most plant vegetative and reproductive tissues. AtPUB41 protein is localized in the cytosol and nucleus. pub41 T-DNA insertion mutants display reduced seed dormancy, and their germination is less inhibited by exogenous ABA than seeds of wild-type plants. pub41 mutant plants are also hypersensitive to drought. ABA induces AtPUB41 promoter activity and steady-state mRNA levels in the roots. Our data suggest that AtPUB41 is a positive regulator of ABA signaling. Main ConclusionArabidopsis ubiquitin ligase PUB41 is induced by ABA and acts as a positive regulator of ABA signaling by modulating seed dormancy, germination, and drought resilience.

plant biology↗

bioRxiv2023

Nucleus-Independent Transgenerational Small RNA Inheritance in C. elegans

Studies using C. elegans nematodes demonstrated that, against the dogma, animals can transmit epigenetic information transgenerationally. While it is now clear that in these worms ancestral RNA interference (RNAi) responses continue to regulate gene expression for many generations, it is still debated whether the primary agent that perpetuates heritable silencing is RNA or chromatin, and whether the information is communicated to the next generation inside or outside of the nucleus. Here we take advantage of the tractability of gene-specific double stranded RNA-induced heritable silencing to answer these questions. We demonstrate that RNAi can be inherited independently of any changes to the chromatin or any other nuclear factors via mothers that are genetically engineered to transmit only their ooplasm but not the oocytes nuclei to the next generation. Nucleus-independent RNA inheritance depends on ZNFX-1, an RNA-binding germ granule resident protein. We find that upon manipulation of normal germ granules functions (in pptr-1 mutants) nucleus-independent RNA inheritance becomes stronger, and can occur even in znfx-1 mutants. Utilizing RNA sequencing, chimeric worms, and sequence polymorphism between different C. elegans isolates, we identify endogenous small RNAs which, similarly to exogenous siRNAs, are inherited in a nucleus-independent manner. From an historical perspective, nucleus-independent inheritance of small RNAs might be regarded as partial vindication of discredited cytoplasmic inheritance theories from the 19th century, such as Darwins "pangenesis" theory.

genetics↗

bioRxiv2022

The ABA INSENSITIVE (ABI) 4 transcription factor is stabilized by stress, ABA and phosphorylation

The Arabidopsis transcription factor ABSCISIC ACID INSENSITIVE 4 (ABI4) is a key player in the plant hormone abscisic acid (ABA) signaling pathway. ABI4 is also involved in seed development and germination, the response to abiotic stresses such as drought and salinity, control of lipid reserve mobilization in the embryo, lateral root formation, and redox control. Expression of the ABI4 gene is tightly regulated and basal expression is low. Maximal transcript levels occur during seed maturation and in the early stages of seed germination and are markedly reduced in other developmental stages. ABI4 is an unstable lowly expressed protein, resulting from tight post-transcriptional regulation. Here, we studied factors affecting the stability of the ABI4 protein using transgenic Arabidopsis plants expressing 35S::HA-FLAG-ABI4-eGFP. Despite the expression of eGFP-tagged ABI4 being driven by the highly active 35S CaMV promoter the steady-state levels of ABI4 were extremely low in the roots of seedling grown in optimal conditions. These levels were markedly enhanced upon exposure of the seedlings to abiotic stress and ABA. ABI4 is degraded rapidly by the 26S proteasome and we report on the role of phosphorylation of ABI4-serine 114 in regulating ABI4 stability. Our results indicate that ABI4 is tightly regulated both post-transcriptionally and post-translationally. Moreover, abiotic factors and plant hormones have similar effects on ABI4 transcripts and ABI4 protein levels. This double-check mechanism for controlling ABI4 reflects on its central role in plant development and cellular metabolism. SIGNIFICANCE STATEMENTWe show that stabilization of the ABI4 transcription factor by stress and hormones is mediated by phosphorylation of Serine 114 by MAP kinases. Transcription of ABI4 is also modulated by MAP kinases, suggesting that the same signals affect both transcript and protein levels, resulting in tight modulation of ABI4 activity.

plant biology↗

bioRxiv2021

The Activity of the Stress Modulated Arabidopsis Ubiquitin Ligases PUB46 and PUB48 is Partially Redundant

The Arabidopsis ubiquitin ligases PUB46, PUB47 and PUB48 are encoded by paralogus genes; pub46 and pub48 mutants display increased drought sensitivity compared to wild type (WT). Although the phenotype displayed in the single gene mutants, suggest that each has specific biological activity, PUB46 and PUB48 activity may be also redundant. To test functional redundancy between two gene products requires a double mutant. Unfortunately, the close proximity of the PUB46 and PUB48 gene loci precludes obtaining a double mutant by crossing the available single mutants. We thus applied microRNA technology to reduce the activity of all three gene products of the PUB46-48 subfamily by constructing an artificial microRNA (aMIR) targeted to this subfamily. Expressing aMIR46-48 in WT plants resulted in increased drought-sensitivity, a phenotype resembling that of the single pub46 and pub48 mutants, and enhanced sensitivity to methyl viologen, similar to that observed for the pub46 mutant. Furthermore, the WT plants expressing aMIR46-48 also revealed reduced inhibition by ABA at seed germination, a phenotype not evident in the single mutants. Expressing aMIR46-48 in pub46 and pub48 mutants further enhanced the drought sensitivity of each parental single mutant and of WT expressing aMIR46-48. Thus, whereas the gene-specific activity of the PUB46 and PUB48 E3s is partially redundant in that absence of either E3 leads to drought sensitivity, our ability to eliminate the activity of both PUB46 and PUB48 in the same plant reveals additional gene specific facets of their activity in the reaction to abiotic stress.

plant biology↗

bioRxiv2020

Phosphorylation of Serine114 of the transcription factor ABSCISIC ACID INSENSITIVE 4 is essential for activity

The transcription factor ABA-INSENSITIVE(ABI)4 has diverse roles in regulating plant growth, including inhibiting germination and reserve mobilization in response to ABA and high salinity, inhibiting seedling growth in response to high sugars, inhibiting lateral root growth, and repressing light-induced gene expression. ABI4 activity is regulated at multiple levels, including gene expression, protein stability, and activation by phosphorylation. Although ABI4 can be phosphorylated at multiple residues by MAPKs, we found that S114 is the preferred site of MPK3. To examine the possible biological role of S114 phosphorylation, we transformed abi4-1 mutant plants with ABI4pro::ABI4 constructs encoding wild type (114S), phosphorylation-null (S114A) or phosphomimetic (S114E) forms of ABI4. Phosphorylation of S114 is necessary for the response to ABA, glucose, salt stress, and lateral root development, where the abi4 phenotype could be complemented by expressing ABI4(114S) or ABI4(S114E) but not ABI4(S114A). Comparison of root transcriptomes in ABA-treated roots of abi4-1 mutant plants transformed with constructs encoding the different phosphorylation-forms of S114 of ABI4 revealed that 85% of the ABI4-regulated genes whose expression pattern could be restored by expressing ABI4(114S) are down-regulated by ABI4. Over half of the ABI4-modulated genes were independent of the phosphorylation state of ABI4; these are enriched for stress responses. Phosphorylation of S114 was required for regulation of 35% of repressed genes, but only 17% of induced genes. The genes whose repression requires the phosphorylation of S114 are mainly involved in embryo and seedling development, growth and differentiation, and regulation of gene expression. HighlightsO_LITranscription factor ABI4 is a substrate of MAP kinases. C_LIO_LIMPK3 preferentially phosphorylates Serine 114 of ABI4. C_LIO_LIPhosphorylated Serine 114 of ABI4 is required for the complementation of abi4 mutants. C_LIO_LIPhosphorylated ABI4 acts primarily as a repressor. C_LI

plant biology↗

bioRxiv2018

Overexpression of Arabidopsis ubiquitin ligase AtPUB46 enhances tolerance to drought and oxidative stress

The U-Box E3 ubiquitin ligase, AtPUB46, functions in the drought response: T-DNA insertion mutants of this single paralogous gene are hypersensitive to water- and oxidative stress (Adler et al. BMC Plant Biology 17:8, 2017). Here we analyze the phenotype of AtPUB46 overexpressing (OE) plants. AtPUB46-OE show increased tolerance to water stress and have smaller leaf blades and reduced stomatal pore area and stomatal index compared with wild type (WT). Despite this, the rate of water loss from detached rosettes is similar in AtPUB46-OE and WT plants. Germination of AtPUB46-OE seeds was less sensitive to salt than WT whereas seedling greening was more sensitive. We observed a complex response to oxidative stress applied by different agents: AtPUB46-OE plants were hypersensitive to H2O2 but hyposensitive to methyl viologen. AtPUB46-GFP fusion protein is cytoplasmic, however, in response to H2O2 a considerable proportion translocates to the nucleus. We conclude that the differential stress phenotype of the AtPUB46-OE does not result from its smaller leaf size but from a change in the activity of a stress pathway(s) regulated by a degradation substrate of the AtPUB46 E3 and also from a reduction in stomatal pore size and index.\n\nAccession NumbersSequence data for this article can be found in: The Arabidopsis Information Resource database (http://www.arabidopsis.org) under accession numbers At5G18320 (PUB46).

plant biology↗

bioRxiv2017

Large-scale rewiring in a yeast hybrid

The merging of genomes in inter-specific hybrids can result in novel phenotypes, including increased growth rate and biomass yield, a phenomenon known as heterosis. We describe a budding yeast hybrid that grows faster than its parents under different environments. Phenotypically, the hybrid progresses more rapidly through cell cycle checkpoints, relieves the repression of respiration in fast growing conditions, does not slow down its growth when presented with ethanol stress, and shows increasing signs of DNA damage. A systematic genetic screen identified hundreds of alleles affecting hybrid growth whose identity vastly differed between the hybrid and its parent and between growth conditions. This large-scale rewiring of allele effects suggests that despite showing clear heterosis, the hybrid is perturbed in multiple regulatory processes. We discuss the possibility that incompatibilities contribute to hybrid vigor by perturbing safeguard mechanisms that limit growth in the parental background.

systems biology↗