Biology subjects

Orosa-Puente, B.

Publications and source records attributed to Orosa-Puente, B..

5 recordsLinked to original sources

bioRxiv2026

HECT-type ligases facilitate autoubiquitination and degradation of other ubiquitin ligases to activate plant immunity

The ubiquitin-proteasome system (UPS) serves as the primary proteolytic machinery in eukaryotes, governing intracellular protein turnover to maintain proteome homeostasis. In plants, the HECT-type UPL3/4 ubiquitin ligases play vital roles in developmental and immune signaling. After ubiquitination by pathway-specific E3 ligases, substrates are physically relayed to proteasome-associated UPL3/4 ligases for further modification, which is necessary for their proteasome-mediated degradation. In this study, we investigated if the cellular influence of UPL3/4 extends beyond their direct role in substrate degradation. We discovered that UPL3/4 govern the ubiquitination not only of a broad array of immune-related substrates, but also of many UPS components, including E3 ligases. UPL3 physically interacts with PUB22, a pathway-specific U-box E3 ligase that negatively regulates immunity. PUB22 is controlled by a phospho-switch that converts it from an instable autoubiquitinated state to a stable phosphorylated E3 ligase that marks substrates for degradation. Remarkably, UPL3 only interacted with unphosphorylated PUB22 and facilitated its autoubiquitination-mediated degradation, thereby promoting the accumulation of PUB22 substrates. Moreover, the compromised immune phenotypes of upl3 upl4 mutant plants were largely dependent on PUB22 and its close paralogues. Thus, UPL3/4 control the stability of immune-related substrates not only through direct ubiquitination, but also indirectly by promoting autoubiquitination of PUB22 ligase and its paralogues. Controlling the stability of autoubiquitinating E3 ligases may be a universal mechanism whereby HECT-type ligases and the proteasomes they associated with, orchestrate cellular proteostasis in eukaryotes. Significance StatementThe ubiquitin-proteasome system (UPS) governs intracellular protein turnover to maintain proteome homeostasis in eukaryotes. Proteasome-associate HECT-type ubiquitin ligases play an important role in processing and degrading substrates delivered to the proteasome by pathway-specific E3 ligases. Here, we discover that in plants, HECT-type ligases not only promote the degradation of substrates, they also modify the E3 ligases that target these substrates to the proteasome. Specifically, HECT-type ligases facilitated or expanded the autoubiquitination of immune-suppressive E3 ligases, resulting in their proteasome-mediated degradation and onset of immunity. Our discoveries suggest that during plant immunity, HECT-type ligases and the proteasomes they associate with, control cellular proteostasis by governing the stabilities of both E3 ligases and their substrates.

plant biology↗

bioRxiv2026

Ubiquitin recognition integrates plant immune signaling by cell-surface and intracellular receptors

Plant immunity is activated by cell-surface and intracellular receptors that detect pathogen-derived molecules. Mutual potentiation between these two receptor types is essential for robust disease resistance, but the mechanisms underpinning integrated dual receptor immunity remain unknown. Here, we found that activation of the intracellular receptor, ZAR1, induces its site-specific modification by non-proteolytic ubiquitin chains. ZAR1-anchored ubiquitin chains promote oligomerization of ZAR1 into a calcium-permeable resistosome pore and are recognized by RH3, a ubiquitin-binding DEAD-box RNA helicase. Remarkably, RH3 recruits both ZAR1 resistosomes and cell-surface receptor components into a dual receptor complex, thereby enhancing calcium-dependent mRNA translation of core defense proteins and establishing robust immunity. These findings identify ubiquitin recognition as the missing link in mutual potentiation of plant immunity by cell-surface and intracellular receptors.

plant biology↗

bioRxiv2025

Light induces Phytochrome B SUMOylation to recruit the immune regulator NPR1 in nuclear condensates to control immunity in plants

It has long been observed that light perception by phytochromes control plant immunity, however, the underpinning molecular mechanism is less well understood. We demonstrate that light mediated SUMO conjugation to Phytochrome B (PhyB) is critical for increasing cellular salicylic-acid (SA) levels to orchestrate systemic acquired resistance (SAR) upon avirulent bacterial infection. SUMOylation is critical for PhyB nuclear condensate formation during light activated immunity. Light induced PhyB SUMOylation recruits NPR1, through its SUMO interacting motif to nuclear condensates to elevate SA levels for immune responses. In the dark during SAR, elevated SA levels substitute for light to maintain PhyB SUMOylation and immune-related photobody formation by stimulating the degradation of PhyB targeting deSUMOylase, OTS1. SUMOylated PhyB-NPR1 immune photobodies associate with TGA transcription factor associated chromatin to trigger immune gene expression. We unravel a mechanism where SUMOylation can enable light to recruit NPR1 to PhyB nuclear condensates to form immune photobodies to regulate plant immunity. HighlightsO_LILight-dependent immunity in plants relies on the SUMO mediated interaction between the photoreceptor PhyB and the Salicylic Acid (SA) receptor NPR1. C_LIO_LILight induced PhyB SUMOylation recruits NPR1 to nuclear condensates which we identify as immune photobodies that elevate SA levels for immune responses. C_LIO_LIIn darkness, SA can replace light in enabling PhyB-NPR1 immune photobody formation by regulating SUMOylation revealing a SA mediated mechanism for controlling PhyB liquid-liquid phase separation. C_LIO_LISUMO-modified PhyB-NPR1 immune photobodies regulate transcriptional activity of immune associated chromatin to shape defence responses in plants. C_LI

plant biology↗

bioRxiv2024

Differential Ubiquitination of Host Proteins in Response to IPNV and ISAV viruses in Atlantic salmon

Viral diseases remain a major barrier to the sustainable production of farmed fish, primarily attributable to the absence of effective prevention and treatment options. Understanding host-pathogen interactions can guide the development of vaccines, antiviral therapies, or gene editing strategies. Ubiquitination is a key cell signalling molecule, known to regulate many aspects of immune functions but currently understudied in fish. This study leverages ubiquitin-enriched mass spectroscopy complemented with RNA sequencing to characterize the role of ubiquitination in response to infection. A challenge experiment was conducted by infecting Atlantic salmon head kidney (SHK-1) cells with Infectious salmon anaemia virus (ISAV) and Infectious pancreatic necrosis virus (IPNV). At 24- and 48 hours post-infection dramatic changes were observed in the global ubiquitination state of host proteins. Many post-translational modifying proteins increased in abundance upon ISAV infection, whilst IPNV infection resulted in a reduction in abundance of many of these proteins. Transcriptomics showed a delay in the activation of the antiviral response to ISAV infection, with major upregulation of genes associated with immune pathways only at 48h. On the contrary, IPNV infection resulted in upregulation of classic innate immune response genes at both timepoints. Clear activation of Rig-like receptor pathways is demonstrated in both infections, in addition to upregulation of both conserved and novel antiviral TRIM E3 ubiquitin ligate genes. Network analysis identified clusters of immune genes and putatively regulatory proteins showing differential ubiquitination upon viral infection. This study highlights the importance of post-translational control of the host innate immune response to viruses in Atlantic salmon. Clear differences in ubiquitination between two viruses indicate either virus-specific post-translational regulation or viral antagonism of the immune response. Additionally, the ubiquitination of various proteins was linked to the regulation of innate immune pathways, suggesting a direct role of ubiquitination in the regulation of antiviral responses. AUTHOR SUMMARYUbiquitination is a main cellular regulatory mechanism in all animal species, controlling the activity of many proteins within the cell. The role of ubiquitination in the regulation of immunity is well-established, and several direct interactions with viruses have been described, either as part of a strategy of the host to fight the infection or as a viral mechanism to evade the host immune response. In aquaculture, viral diseases currently represent the most important threat to the sustainability of the industry. However, very little is known about the interplay between ubiquitination and viral pathogens in fish species. In our study, we have assessed the ubiquitination response of Atlantic salmon to two production-relevant viruses, Infectious salmon anaemia virus (ISAV) and Infectious pancreatic necrosis virus (IPNV). We found remarkable differences in the ubiquitination profiles between the two infections, suggesting a key role of ubiquitination on the early immune response. We also discovered an association between the ubiquitination of certain regulatory proteins and the activation of antiviral pathways. This information could help develop new strategies to tackle viral diseases in aquaculture, such as the development of more effective vaccines or antiviral therapies, or inform gene editing efforts to generate disease resistant fish.

molecular biology↗

bioRxiv2021

Proteasome-associated ubiquitin ligase relays target plant hormone-specific transcriptional activators

The ubiquitin-proteasome system is vital to hormone-mediated developmental and stress responses in plants. Ubiquitin ligases target hormone-specific transcriptional activators (TAs) for degradation, but how TAs are processed by proteasomes remains unknown. We report that in Arabidopsis the salicylic acid-and ethylene-responsive TAs, NPR1 and EIN3, are relayed from pathway-specific ubiquitin ligases to proteasome-associated HECT-type UPL3/4 ligases. Activity and stability of NPR1 was regulated by sequential action of three ubiquitin ligases, including UPL3/4, while proteasome processing of EIN3 required physical handover between ethylene-responsive SCFEBF2 and UPL3/4 ligases. Consequently, UPL3/4 controlled extensive hormone-induced developmental and stress-responsive transcriptional programmes. Thus, our findings identify unknown ubiquitin ligase relays that terminate with proteasome-associated HECT-type ligases, which may be a universal mechanism for processive degradation of proteasome-targeted TAs and other substrates. One-Sentence SummaryTranscriptional activators are targeted by proteasomal ubiquitin ligase relays that control their activity and stability.

plant biology↗