Proteasomes accumulate in the plant apoplast where they participate in microbe-associated molecular pattern (MAMP)-triggered pathogen defense.

Akin to mammalian extracellular fluids, the plant apoplastic fluid (APF) contains a unique collection of proteins, RNAs, and vesicles that drive many physiological processes ranging from cell wall assembly to defense against environmental challenges. Using an improved method to enrich for the Arabidopsis APF, we better define its composition and discover that the APF harbors active proteasomes though microscopic detection, proteasome-specific activity and immunological assays, and mass spectrometry showing selective enrichment of the core protease. Functional analysis of extracellular (ex)-proteasomes reveals that they help promote basal pathogen defense through proteolytic release of microbe-associated molecular patterns (MAMPs) such as flg22 from bacterial flagellin that induce protective reactive-oxygen-species (ROS) bursts.

Global impacts of peroxisome and pexophagy dysfunction revealed through multi-omics analyses of lon2 and atg2 mutants.

Peroxisomes house diverse metabolic pathways that are essential for plant and animal survival, including enzymes that produce or inactivate toxic byproducts. Despite the importance of peroxisomes and their collaborations with other organelles, the mechanisms that trigger or prevent peroxisome turnover and the cellular impacts of impaired peroxisomes are incompletely understood. When Arabidopsis thaliana LON2, a peroxisomal protein with chaperone and protease capacity, is disrupted, metabolic dysfunction and protein instability in peroxisomes ensue.

Signaling by a bacterial phytochrome histidine kinase involves a conformational cascade reorganizing the dimeric photoreceptor.

Phytochromes (Phys) are a divergent cohort of bili-proteins that detect light through reversible interconversion between dark-adapted Pr and photoactivated Pfr states. While our understandings of downstream events are emerging, it remains unclear how Phys translate light into an interpretable conformational signal. Here, we present models of both states for a dimeric Phy with histidine kinase (HK) activity from the proteobacterium Pseudomonas syringae, which were built from high-resolution cryo-EM maps (2.

Crystal structure of the photosensory module from a PAS-less cyanobacterial phytochrome as Pr shows a mix of dark-adapted and photoactivated features.

Phytochromes (Phys) are a diverse collection of photoreceptors that regulate numerous physiological and developmental processes in microorganisms and plants through photointerconversion between red-light-absorbing Pr and far-red light-absorbing Pfr states. Light is detected by an N-terminal photo-sensing module (PSM) sequentially comprised of Period/ARNT/Sim (PAS), cGMP-phosphodiesterase/adenylyl cyclase/FhlA (GAF), and Phy-specific (PHY) domains, with the bilin chromophore covalently-bound within the GAF domain. Phys sense light via the Pr/Pfr ratio measured by the light-induced rotation of the bilin D-pyrrole ring that triggers conformational changes within the PSM, which for microbial Phys reaches into an output region.