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Author(s): Shuai Huang [sup.1] [sup.2] [sup.3] [sup.4] , Shiwei Zhu [sup.1] [sup.2] [sup.3] [sup.4] , Pradeep Kumar [sup.1] [sup.2] [sup.3] [sup.4] , John D. MacMicking [sup.1] [sup.2] [sup.3] [sup.4] Author [...], Liquid-liquid phase separation (LLPS) has emerged as a central paradigm for understanding how membraneless organelles compartmentalize diverse cellular activities in eukaryotes.sup.1-3. Here we identify a superfamily of plant guanylate-binding protein (GBP)-like GTPases (GBPLs) that assemble LLPS-driven condensates within the nucleus to protect against infection and autoimmunity. In Arabidopsis thaliana, two members of this family--GBPL1 and GBPL3--undergo phase-transition behaviour to control transcriptional responses as part of an allosteric switch that is triggered by exposure to biotic stress. GBPL1, a pseudo-GTPase, sequesters catalytically active GBPL3 under basal conditions but is displaced by GBPL3 LLPS when it enters the nucleus following immune cues to drive the formation of unique membraneless organelles termed GBPL defence-activated condensates (GDACs) that we visualized by in situ cryo-electron tomography. Within these mesoscale GDAC structures, native GBPL3 directly bound defence-gene promoters and recruited specific transcriptional coactivators of the Mediator complex and RNA polymerase II machinery to massively reprogram host gene expression for disease resistance. Together, our study identifies a GBPL circuit that reinforces the biological importance of phase-separated condensates, in this case, as indispensable players in plant defence. A family of plant guanylate-binding protein-like GTPases controls phase separation and assembly of condensates, thereby forming a circuit that regulates transcriptional responses to biotic stress.

Author(s): Xiaowei Han [sup.1] , Florian Altegoer [sup.2] , Wieland Steinchen [sup.2] , Lynn Binnebesel [sup.2] , Jan Schuhmacher [sup.2] [sup.6] , Timo Glatter [sup.3] , Pietro I. Giammarinaro [sup.2] [...], Fungi-induced plant diseases affect global food security and plant ecology. The biotrophic fungus Ustilago maydis causes smut disease in maize (Zea mays) plants by secreting numerous virulence effectors that reprogram plant metabolism and immune responses.sup.1,2. The secreted fungal chorismate mutase Cmu1 presumably affects biosynthesis of the plant immune signal salicylic acid by channelling chorismate into the phenylpropanoid pathway.sup.3. Here we show that one of the 20 maize-encoded kiwellins (ZmKWL1) specifically blocks the catalytic activity of Cmu1. ZmKWL1 hinders substrate access to the active site of Cmu1 through intimate interactions involving structural features that are specific to fungal Cmu1 orthologues. Phylogenetic analysis suggests that plant kiwellins have a versatile scaffold that can specifically counteract pathogen effectors such as Cmu1. We reveal the biological activity of a member of the kiwellin family, a widely conserved group of proteins that have previously been recognized only as important human allergens.A kiwellin protein in maize is found to inhibit the activity of the secreted enzyme chorismate mutase from a maize-infecting pathogenic fungus, suggesting a role for kiwellins in plant immunity.

Soybean (Glycine max (L.) Merr.) is an important crop that provides a sustainable source of protein and oil worldwide. Soybean cyst nematode (Heterodera glycines Ichinohe) is a microscopic roundworm that [...]

Author(s): Zhenyu Cheng [1, 2]; Jian-Feng Li [1, 2]; Yajie Niu [1, 2]; Xue-Cheng Zhang [1, 2]; Owen Z. Woody [3]; Yan Xiong [1, 2]; Slavica Djonovi[c acute] [1, 2]; [...]