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PubMed2024

Dissecting OGT's TPR domain to identify determinants of cellular function.

O-GlcNAc transferase (OGT) is an essential mammalian enzyme that glycosylates myriad intracellular proteins and cleaves the transcriptional coregulator Host Cell Factor 1 to regulate cell cycle processes. Via these catalytic activities as well as noncatalytic protein-protein interactions, OGT maintains cell homeostasis. OGT's tetratricopeptide repeat (TPR) domain is important in substrate recognition, but there is little information on how changing the TPR domain impacts its cellular functions. Here, we investigate how altering OGT's TPR domain impacts cell growth after the endogenous enzyme is deleted. We find that disrupting the TPR residues required for OGT dimerization leads to faster cell growth, whereas truncating the TPR domain slows cell growth. We also find that OGT requires eight of its 13 TPRs to sustain cell viability. OGT-8, like the nonviable shorter OGT variants, is mislocalized and has reduced Ser/Thr glycosylation activity; moreover, its interactions with most of wild-type OGT's binding partners are broadly attenuated. Therefore, although OGT's five N-terminal TPRs are not essential for cell viability, they are required for proper subcellular localization and for mediating many of OGT's protein-protein interactions. Because the viable OGT truncation variant we have identified preserves OGT's essential functions, it may facilitate their identification.

N-Acetylglucosaminyltransferases↗

PubMed2025

Spatio-genetically coordinated TPR domain-containing proteins modulate c-di-GMP signaling in Vibrio vulnificus.

Vibrio species, which include several pathogens, are autochthonous to estuarine and warm coastal marine environments, where biofilm formation bolsters their ecological persistence and transmission. Here, we identify a bicistronic operon, rcbAB, whose products synergistically inhibit motility and promote biofilm maturation post-attachment by modulating intracellular c-di-GMP levels in the human and animal pathogen V. vulnificus. RcbA contains an N-terminal tetratricopeptide repeat (TPR) domain and a structured C-terminal region of unknown function, while RcbB possesses an N-terminal TPR domain and a C-terminal GGDEF domain characteristic of diguanylate cyclases. The TPR domain of RcbB represses its diguanylate cyclase activity, while RcbA's TPR domain and C-terminal region co-operatively de-repress it. Localization of both proteins to the flagellar pole is TPR-dependent but not co-dependent, although RcbA anchors RcbB to the pole in the absence of polar landmarks such as HubP and flagella. The conservation of rcbAB across diverse bacterial taxa substantiates its fundamental importance in bacterial biology. This work demonstrates how spatio-genetically coordinated TPR domain-containing proteins modulate c-di-GMP signaling, contributing to our understanding of biofilm formation in Vibrio species and potentially other bacteria. It also reveals the first evidence of inter-protein interaction via the TPR domains of both partners, challenging the conventional paradigm in which only one bears the domain.

Vibrio vulnificus↗

PubMed2026

Transgenic overexpression of GmAPC7-CT improves seed yield and reduces susceptibility to soybean mosaic virus and Meloidogyne incognita in soybean.

Stable transgenic soybean lines overexpressing the GmAPC7-CT gene have demonstrated increased seed yield and reduced susceptibility to the soybean mosaic virus and Meloidogyne incognita. The Anaphase-Promoting Complex subunit 7 (APC7) is a core structural component of the anaphase-promoting complex or cyclosome (APC/C). The terminal region of this AtAPC7 gene has been shown in Arabidopsis thaliana to accumulate more transcripts than the full-length gene. The AtAPC7-CT gene (terminal region of the AtAPC7) encodes a protein with significant homology to a tobacco viral replication inhibitor (IVR). Its stable overexpression in transgenic A. thaliana lines resulted in notable improvements in biomass, seed yield, earliness of vegetative-reproductive transitions, and reduced susceptibility to viruses. In this study, we generated stable transgenic soybean lines overexpressing the GmAPC7-CT gene (terminal region or 3' portion of Glyma.15G096000, corresponding to the AtAPC7-CT) and evaluated seed yield and susceptibility of these lines to soybean mosaic virus and Meloidogyne incognita. The GmAPC7-CT gene is 624 nucleotides long and encodes a 207-amino acid protein with two tetratricopeptide repeat (TPR) domains. GmAPC7-CT showed 100% amino acid identity with full-length GmAPC7, 81.16% identity with AtAPC7-CT, and 87.94% identity with tobacco IVR. Stable transgenic lines demonstrated significant advancements in plant development and seed yield, with the top three lines producing up to 43% more pods, 44% more seeds, and a 16% increase in seed weight. Furthermore, these soybean lines showed up to a 70% reduction in susceptibility to soybean mosaic virus and M. incognita, reflected by decreased viral RNA load and nematode reproduction factor. Collectively, these results support a conserved role of GmAPC7-CT in soybean and AtAPC7-CT in A. thaliana, acting similarly to the tobacco IVR. Thus, our findings underscore the strong biotechnological potential of the GmAPC7-CT gene to improve key agronomic traits in soybean through genetic engineering approaches, including conventional breeding, transgenesis, and genome editing.

Glycine max↗

PubMed2026

Host genetic regulation of xylem-resident Pseudomonas enhances cucumber growth.

BACKGROUND: Although endophytic microorganisms play a critical role in plant growth and stress resilience, the genetic basis underlying host selection of beneficial microbiota-particularly within the xylem-remains poorly understood. Cucumber (Cucumis sativus), as a crop model with a well-developed system for studying vascular biology, offers a valuable system to investigate the host genetic determinants of xylem microbiome assembly. RESULTS: By conducting population-level microbiome profiling across 109 cucumber accessions, we identified a conserved xylem microbiota dominated by Proteobacteria. Within this community, 20 core amplicon sequence variants (ASVs) were consistently present in xylem sap. Genome-wide association mapping identified a host genetic locus, CsXPR1, which encodes a tetratricopeptide repeat protein that regulates the abundance of the dominant xylem-colonized Pseudomonas ASV_4. Colonization patterns of ASV_4 varied across host genotypes and were correlated with CsXPR1 expression levels, suggesting a precision genetic regulation of bacterial entry into vascular tissues. Pseudomonas fulva strain 220, with 97% 16S rRNA gene identity with ASV_4, could colonize in cucumber xylem by inoculation of either roots or leaves. Genome analysis and plate assays revealed the biosynthesis of indole-3-acetic acid (IAA), solubilization of phosphate, and a range of plant beneficial traits in strain 220. Inoculation with strain 220 significantly enhanced growth in cucumber, but only in CsXPR1 haplotype that exhibited high gene expression and higher recruitment capacity of the strain. These benefits included notable increases in plant height (38%), stem diameter (36%), leaf area (61%), fresh and dry weight (51% and 85%, respectively), and a 4.57-fold increase in 4-methyleneglutamine content within the xylem sap. CONCLUSION: Our findings reveal a complete "gene-to-function" pathway where the host gene CsXPR1 mediates a genotype-dependent growth promotion. It achieves this by regulating the xylem colonization of a beneficial bacterium, Pseudomonas fulva, which in turn enhances plant growth by enriching the xylem sap with the key metabolite 4-methyleneglutamine. Video Abstract.

Cucumis sativus↗