Biology subjects

Uestuen, S.

Publications and source records attributed to Uestuen, S..

4 recordsLinked to original sources

bioRxiv2026

Gene repertoire expansion and cis-regulatory diversification shaped 26S proteasome evolution within a proteostasis-centered network

The 26S proteasome is essential for proteostasis and constitutes one of the most conserved molecular machineries in eukaryotes. Its homeostasis is maintained by a mechanistically conserved feedback loop involving kingdom-specific components. Yet, how the proteasome subunits and associated regulatory feedback loop have evolved to accommodate ever-changing cellular context is poorly understood. Here, we combine gene duplicate analysis, cis-regulatory element identification, functional validation, and protein network inference to investigate the evolution of plant 26S proteasome. Proteasome gene repertoires expanded largely independently across plant lineages, with paralogs showing shifts in post-translational modification sites and pronounced transcriptional divergence in response to environmental cues. Comparative analysis of 26S proteasome gene promoters revealed extensive diversification of proteasome-associated cis-elements across plants, with repeated enrichment of related motifs. These observations led to the identification of telomere repeat-binding proteins (TRBs) as novel transcriptional regulators of proteasome genes in A. thaliana, through association with the previously characterized PRCE motif. Finally, evolutionary rate covariation analysis identified a conserved proteasome-associated network connected through proteasome-associated cis-elements and unifying cellular proteostasis. Together, our results indicate that plant 26S proteasome is controlled by a regulatory architecture that combines conserved cis-regulatory mechanisms, lineage-specific innovation, and stress-responsive paralog specialization at the center of the proteostasis network; offering a new perspective on the evolution of one of the most essential molecular complexes.

plant biology↗

bioRxiv2024

XopM, a FFAT motif containing type-III effector protein from Xanthomonas, suppresses PTI responses at the plant plasma membrane

Many Gram-negative pathogenic bacteria use type-III effector proteins (T3Es) as essential virulence factors to suppress host immunity and to cause disease. However, in many cases the molecular function of T3Es remains unknown. The plant pathogen Xanthomonas campestris pv. vesicatoria (Xcv) is the causal agent of bacterial spot disease on tomato and pepper plants and is known to translocate around 30 T3Es into its host cell, which collectively suppress plant defense and promote infection. XopM is an Xcv core T3E with unknown function that has no similarity to any other known protein. We found that XopM interacts with vesicle-associated membrane protein (VAMP)-associated proteins (VAPs) in an isoform specific manner. The endoplasmic reticulum (ER) integral membrane protein VAP is a common component of membrane contact sites involved in both tethering and lipid transfer by binding directly to proteins containing a FFAT [two phenylalanines (FF) in an acidic tract (AT)] motif. Sequence analyses revealed that XopM displays two FFAT motifs that cooperatively mediated the interaction of XopM with VAP. When expressed in plants, XopM supports growth of a non-pathogenic bacterial strain and dampens the production of reactive oxygen species, indicating its ability to suppress plant immunity. Further analyses revealed that the interaction with VAP and the ability to suppress PTI are structurally and functionally separable. Although XopM requires localization to the host membrane system for full PTI suppression activity. We discuss a working model in which XopM uses FFAT-motifs to target the membrane in order to interfere with early PTI responses.

plant biology↗

bioRxiv2021

Proteasome homeostasis is essential for a robust cauliflower mosaic virus infection

The ubiquitin-proteasome system (UPS) is essential for the maintenance and shifts in protein homeostasis, and thereby forms a founding pillar in virtually all cellular processes including plant immunity and viral infections. According to its importance in fine-tuning the complex plant immune response, proteasomal defects result in divergent outcomes including both resistance and susceptibility phenotypes in response to viruses. The final outcome will largely depend on the specific virus and its specific co-adaptation with the UPS as well as the immune system. Here, we show that cauliflower mosaic virus (CaMV) relies on the proteasome for robust infection. The proteasome system is induced during infection via SA and supports systemic accumulation of the virus as well as plant growth performance during infection. This establishes the UPS as a win-win pathway for the plant and the virus, and together with our demonstration of a proteasome-suppressing viral effector, the intimacy between the proteasome and CaMV is fortified.

plant biology↗

bioRxiv2021

Self-ubiquitination of a pathogen type-III effector traps and blocks the autophagy machinery to promote disease

Beyond its role in cellular homeostasis, autophagy plays anti- and pro-microbial roles in host-microbe interactions, both in animals and plants. One prominent role of anti-microbial autophagy is to degrade intracellular pathogens or microbial molecules, in a process termed xenophagy. Consequently, microbes evolved mechanisms to hijack or modulate autophagy to escape elimination. Although well-described in animals, the extent to which xenophagy contributes to plant-bacteria interactions remains unknown. Here, we provide evidence that Xanthomonas campestris pv. vesicatoria (Xcv) suppresses host autophagy by utilizing type-III effector XopL. XopL interacts with and degrades the autophagy component SH3P2 via its E3 ligase activity to promote infection. Intriguingly, XopL is targeted for degradation by defense-related selective autophagy mediated by NBR1/Joka2, revealing a complex antagonistic interplay between XopL and the host autophagy machinery. Our results implicate plant antimicrobial autophagy in depletion of a bacterial virulence factor and unravels an unprecedented pathogen strategy to counteract defense-related autophagy.

plant biology↗