XCP1 cleaves Pathogenesis-related protein 1 into CAPE9 for systemic immunity in Arabidopsis.

Proteolytic activation of cytokines regulates immunity in diverse organisms. In animals, cysteine-dependent aspartate-specific proteases (caspases) play central roles in cytokine maturation. Although the proteolytic production of peptide cytokines is also essential for plant immunity, evidence for cysteine-dependent aspartate-specific proteases in regulating plant immunity is still limited. In this study, we found that the C-terminal proteolytic processing of a caspase-like substrate motif "CNYD" within Pathogenesis-related protein 1 (PR1) generates an immunomodulatory cytokine (CAPE9) in Arabidopsis. Salicylic acid enhances CNYD-targeted protease activity and the proteolytic release of CAPE9 from PR1 in Arabidopsis. This process involves a protease exhibiting caspase-like enzyme activity, identified as Xylem cysteine peptidase 1 (XCP1). XCP1 exhibits a calcium-modulated pH-activity profile and a comparable activity to human caspases. XCP1 is required to induce systemic immunity triggered by pathogen-associated molecular patterns. This work reveals XCP1 as a key protease for plant immunity, which produces the cytokine CAPE9 from the canonical salicylic acid signaling marker PR1 to activate systemic immunity.

Effect of 1,3-Propane Sultone on the Formation of Solid Electrolyte Interphase at Li-Ion Battery Anode Surface: A First-Principles Study.

Density functional theory is applied to investigate the reductive reactions of reductive-type additive, 1,3-propane sultone (PS), on the formation of solid electrolyte interphase (SEI) near the lithium-ion battery anode surface. Different from the studies that mostly focus on the reduction dissociation of a specific molecule, we adopt an iterative method that systematically considered most possible reactants from the environment in every round of the reaction. The thermodynamically favorable reaction in each round was chosen. Its products then proceed to the following step. At least four iterations of reactions were calculated. The favorable products in each round were then analyzed to understand the trend of the series reactions. With the iterative method, the compounds in every reaction round can be inspected in detail. The method not only predicted the compounds that are consistent with those observed in the experiments but also provide insights into how PS forms an effective SEI. In the solvent state, the most stable reduction states of PS and electrolyte ethylene carbonate (EC) are confirmed as the initial reactants further interact with the environment supplies. First, with the addition of PS, the reduction of PS is prior to EC, which would suppress the reduction of EC and decrease the generation of ethene gas. Second, the compounds from the initial reaction round of PS are lithiated ones and show higher reduction ability than that of EC, while the latter show lower reduction ability than that of the EC, which terminated the reactions. This would be the critical properties for reductive-type additive to form an effective SEI film.