Biology subjects

Grey, H.

Publications and source records attributed to Grey, H..

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

Mobile immune signals potentiate salicylic acid-mediated plant immunity via WRKY38/62 transcription factors

Systemic acquired resistance (SAR) is a broad-spectrum plant immune response that provides protection against various pathogens. Activation of SAR requires mobile immune signals as well as the indispensable immune hormone salicylic acid (SA). Nonetheless, it remains unknown how mobile signals integrate with the SA signal to produce functional SAR responses. Here, we demonstrate that the mobile signals, azelaic acid (AzA) and N-hydroxy-pipecolic acid (NHP), respectively dampened and potentiated SA-induced transcriptional reprogramming of thousands of genes. Indeed, NHP enhanced stability of the SA receptor protein NPR1, and unlike AzA, it dramatically increased the effectiveness of SA-induced immunity against bacterial infection by 10-fold. Analysis of NHP-primed, SA-responsive gene promoters indicated that WRKY transcription factors play an important role in integrating these two immune signals. While responsiveness to SA remained largely unaffected by mutation of WRKY38 and WRKY62, it abolished NHP-mediated potentiation of SA-induced gene expression and immunity. Collectively, our findings reveal mobile signals potentiate SA-mediated plant immunity via WRKY38/62 transcription factors. TeaserActivation of broad-spectrum immunity in plants requires mutual potentiation between multiple distinct immune signals.

plant 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↗

bioRxiv2019

Investigating mechanisms of polarized light sensitivity in the small white butterfly Pieris rapae

There is an ever increasing number of arthropod taxa shown to have polarization sensitivity throughout their compound eyes. However, the mechanisms underlying arthropod perception of polarized reflections from objects such as plants are not well understood. The small white butterfly, Pieris rapae, has been demonstrated to exploit foliar polarized reflections, specifically the degree of linear polarization (DoLP), to recognize host plants. The well-described visual system of P. rapae includes several photoreceptor types (red, green, blue) that are sensitive to polarized light. Yet, the mechanism underlying the behavioral responses of P. rapae to stimuli with different DoLPs remains unknown. To investigate potential mechanisms, we designed several two-choice behavioral bioassays, displaying plant images on paired LCD monitors which allowed for independent control of polarization, color and intensity. We found that shifts in image intensity had a similar effect on P. rapae preferences for stimuli dissimilar in DoLP and dissimilar in color, suggesting DoLP differences are perceived as color. When a DoLP choice was offered between plant images manipulated in a manner to minimizing the response of blue, red, or blue and red photoreceptors, P. rapae shifted its preference for DoLP, suggesting a role for red, green and blue polarization-sensitive photoreceptors. Modeling of P. rapae photoreceptor responses to test stimuli suggests that differential DoLP is not perceived solely as a color difference. Our combined results suggest that P. rapae females process and interpret polarization reflections in a way different from that described for other polarization-sensitive taxa.

animal behavior and cognition↗