Biology subjects

Dunger, G.

Publications and source records attributed to Dunger, G..

3 recordsLinked to original sources

bioRxiv2026

Cryo-EM structure analysis of phage {Phi}Xacm4-11 that infects the phytopathogen Xanthomonas citri

Very few bacteriophages that infect Xanthomonas species have been characterized genetically and only one 3D structure, the capsid of a siphovirus that infects the phytopathogen Xanthomonas citri, has been determined at high resolution. This study presents the annotated DNA sequence and detailed structural analysis of {Phi}Xacm4-11, a podovirus that infects Xanthomonas citri, shedding light on its unique architecture and functional attributes, providing insights into the molecular mechanisms underlying host recognition and infection. Annotation of the genome revealed conserved features among related phages, but also distinct genetic elements that may contribute to {Phi}Xacm4-11s specificity toward X. citri. Genes associated with host recognition and infection were identified, including the genes potentially coding for the receptor-binding proteins (RBPs) at the tail fibre tip, offering insights into their role in bacterial attachment. Using high-resolution cryo-electron microscopy, we resolved the architecture of the mature, pre-released virion, revealing a T7-like head-tail assembly with a well-defined portal-tail complex embedded at a unique fivefold vertex. Our findings provide a detailed view of the structural and functional components of {Phi}Xacm4-11, furthering our understanding of its molecular interactions with X. citri and its potential application in phage therapy against phytopathogens. SIGNIFICANCE STATEMENTBacteriophages are increasingly recognized as powerful tools to control bacterial pathogens in medicine and agriculture, yet the structural basis of host recognition and genome delivery remains poorly understood for most phages. Here, we present a comprehensive structural and functional analysis of {Phi}Xacm4-11, a podovirus that infects the plant pathogen Xanthomonas citri. By combining genome annotation, proteomics, and high-resolution cryo-electron microscopy, we reveal the complete architecture of the mature virion and its specialized portal-tail machinery. Our results show how this short-tailed phage deploys an internal injection device to penetrate the bacterial cell envelope and highlight structural features linked to type IV pilus-dependent infection. These findings provide insights into phage entry mechanisms and establish {Phi}Xacm4-11 as a model for engineering biocontrol strategies.

biochemistry↗

bioRxiv2025

Maize mutant hybrids with improved drought tolerance and increased yield in a field experimental setting

Previous studies determined that maize mutants in miR394-regulated genes, ZmLCR1 and ZmLCR2, are more tolerant than wild-type seedlings to prolonged periods of drought. In order to evaluate the effect of these mutations in a genetic background more similar to that of maize commercialization, in this work we evaluate growth of double mutant hybrid plants in W22/B73 genetic background and also evaluated plant fitness, flowering and yield in experimental plots under two watering regimes, and compared the nutritional content of wild-type and mutant hybrids. Our results show that mutant hybrid seedlings exhibit improved physiology under normal watering conditions as well as in drought conditions, exhibiting an increase in epicuticular wax content, unaltered membrane damage in drought and lower ROS production, supporting higher survival after severe drought for double mutant hybrid seedlings. We also established that the hybrid mutants grown in typical agricultural conditions do not show differences in flowering time or in physiological and nutritional aspects, but they present a higher yield in comparison to wild-type W22/B73 hybrids, as determined by higher ear weight and number of kernels per ear in mutant hybrids, when grown in field rainfed conditions. HighlightsO_LIDouble mutants in miR394-regulated genes, ZmLCR1 and ZmLCR2, show enhanced drought tolerance in hybrid maize seedlings, with improved physiological traits under both normal and stress conditions. C_LIO_LIMutant hybrids exhibit increased epicuticular wax accumulation and reduced ROS production, supporting greater survival during prolonged drought stress. C_LIO_LIField-grown mutant hybrids in a W22/B73 background maintain normal flowering time and nutritional composition, indicating no agronomic penalties from the mutations. C_LIO_LIYield is significantly higher in mutant hybrids compared to wild-type controls, as shown by increased ear weight and kernel number under rainfed field conditions. C_LIO_LIThese findings highlight ZmLCR1 and ZmLCR2 as valuable targets for breeding drought-tolerant, high-yielding maize cultivars suited to production environments. C_LI

plant biology↗

bioRxiv2023

The protective function of an immunity protein against the cis-toxic effects of a Xanthomonas Type IV Secretion System Effector

Many bacterial species use specialized secretion systems to translocate proteinaceous toxic effectors into target bacterial cells. In most cases, effectors are encoded in bicistronic operons with their cognate immunity proteins. The current model is that immunity proteins could, in principle, provide protection in two different ways: i) by avoiding self-intoxication (suicide or cis-intoxication) or ii) by inhibiting intoxication due to "friendly-fire" translocation from neighboring sister cells (fratricide or trans-intoxication). Here, we set out to distinguish between these two protection mechanisms in the case of the bactericidal Xanthomonas citri Type IV Secretion System (X-T4SS), where killing is due to the action of a cocktail of secreted effectors (X-Tfes) that are inhibited by their cognate immunity proteins (X-Tfis). We use a set of X. citri mutants lacking multiple X-Tfe/X-Tfi pairs to show that X-Tfis are not absolutely required to protect against trans-intoxication. Our investigation then focused on the in vivo function of the lysozyme-like effector X-TfeXAC2609 and its cognate immunity protein X-TfiXAC2610. We observe the accumulation of damage in the X. citri cell envelope and inhibition of biofilm formation due to the action of X-TfeXAC2609 in the absence of X-TfiXAC2610. We show that X-TfeXAC2609 toxicity is independent of an active X-T4SS and that X-TfiXAC2610 protects the cell colony against X-TfeXAC2609-induced cis-intoxication via autolysis. In vitro assays employing X-TfiXAC2610 mutants were used to test and validate an AlphaFold2-derived model of the X-TfeXAC2609-X-TfiXAC2610 complex which presents topological similarities with the distantly related Tse1/Tsi1 complex from P. aeruginosa and the the i-type lysozyme from Meretrix lusoria (MI-iLys) in complex with PliI-Ah from Aeromonas hydrophila. While immunity proteins in other systems have been shown to protect against attacks by sister cells (trans-intoxication), this is the first description of an antibacterial secretion system in which the immunity proteins are dedicated to protecting cells against cis-intoxication.

biochemistry↗