Publications

4807

ABSTRACT Citrus Huanglongbing (HLB), caused by ‘ Candidatus Liberibacter asiaticus’ ( Ca Las), is the most devastating disease affecting the global citrus industry. Here, we reported that the Ca Las effector SDE70 promotes HLB pathogenicity by targeting the citrus ubiquitination pathway. Transgenic expression of SDE70 in Wanjincheng orange ( Citrus sinensis Osbeck) accelerated early Ca Las proliferation, aggravated HLB symptoms, and increased susceptibility to citrus canker induced by Xanthomonas citri subsp. citri ( Xcc ). These results demonstrate that SDE70 functions as a broad‐spectrum suppressor of citrus immunity. Mechanistically, SDE70 physically interacts with CsRUB2, a citrus ubiquitin‐related protein. Furthermore, CsRUB2 overexpression in Wanjincheng oranges reduced resistance to HLB but enhanced resistance to citrus canker. Both SDE70 and CsRUB2 elevated salicylic acid (SA) and hydrogen peroxide (H 2 O 2 ) levels in transgenic plants while lowering methyl salicylate (MeSA) levels. CsRUB2 also decreased jasmonic acid (JA). In contrast to the suppressive effect of SDE70, CsRUB2 enhanced the transcription of citrus immunity genes. Transient expression assays further demonstrated that the SDE70–CsRUB2 interaction dysregulates citrus immunity by perturbing SA, MeSA, JA, and H 2 O 2 signals. These findings provide a theoretical basis for understanding citrus– Ca Las interactions and breeding citrus varieties with broad‐spectrum resistance to both HLB and citrus canker.

Strain IMCC14736, isolated from Korean coastal seawater by dilution-to-extinction culturing, represents a novel member of the OM43 clade within Methylophilaceae. The complete genome consists of a single contig of 1,286,469 bp with a DNA G + C content of 34.3% and encodes 1,358 predicted proteins. Genomic analysis revealed lanthanide-dependent methanol dehydrogenase genes and related C1 metabolism pathways. Based on phylogenetic evidence, the authors propose the name "Candidatus Methylolitoribacter marinus" for this strain.

Persian lime (Citrus latifolia Tan.) is a crop of high economic and social relevance in Mexico due to its nutritional properties, associated health benefits, and particularly the foreign exchange generated through exportation. In recent years, the state of Veracruz has become the leading production region for this species at the national level. However, this crop is susceptible to several vascular diseases that cause significant economic losses in the citrus industry. Among these, Huanglongbing (HLB) is considered the most destructive disease, exerting the greatest impact on Persian lime production. This study involved the collection of Persian lime leaf tissues from different sources: field-grown plants, certified nursery plants, and plants previously sanitized through micrografting and thermotherapy processes. Genomic DNA was extracted from the collected samples. DNA integrity was verified by agarose gel electrophoresis and quantified using a NanoDrop One-C spectrophotometer. Quantitative Real-Time Polymerase PCR (qPCR) was performed using a QuantStudio One thermocycler and SYBR Green Master Mix as the fluorescent detection system. Samples were considered HLB-positive when the cycle threshold (Ct) value was below 35 during the quantification of Candidatus Liberibacter asiaticus. The results support the early, precise, and efficient detection of CLas by qPCR in Persian lime plants, thereby contributing to improved diagnostic and phytosanitary management strategies for this crop.

Abstract Sulfoquinovose, a sulfonated sugar derived from the thylakoid membrane lipid sulfoquinovosyl diacylglycerol, is abundant in photosynthetic organisms and plays a key role in global sulfur cycling. Its degradation in nature is mediated by specialized bacteria, many of which rely on the enzyme sulfoquinovosidase (YihQ) to release sulfoquinovose from sulfoquinovosyl (diacyl)glycerol. Despite its ecological importance, the diversity and functional roles of sulfoquinovose-degrading microorganisms remain poorly characterized in natural environments. Here, we developed a yihQ-targeted amplicon sequencing approach to investigate the richness and distribution of SQ-degrading bacteria across selected environments. We revealed high richness of yihQ-containing microorganisms in the analyzed cow rumen samples, far exceeding that observed in human and mouse gut microbiomes, suggesting an important role of sulfoquinovose metabolism in ruminant digestion. Anoxic microcosm experiments with sulfoquinovose-amended rumen fluid revealed cooperative microbial degradation of sulfoquinovose to sulfide via isethionate cross-feeding. Amplicon sequencing and genome-resolved metagenomics and metatranscriptomics identified yet undescribed and uncultured sulfoquinovose-degrading taxa. Members of Caproiciproducens (Acutalibacteraceae), Candidatus Limivicinus (Oscillospiraceae), and Sphaerochaetaceae transcribed the isethionate-producing sulfo-transketolase pathway, whereas isethionate was likely respired by a Candidatus Mailhella bacterium (Desulfovibrionaceae). This study presents a functional gene-based assay for tracking environmental yihQ richness, highlights sulfoquinovose degradation as a central metabolic process in the cow rumen, describes previously unknown sulfoquinovose-metabolizing bacteria, and advances understanding of sulfur physiology in complex microbial communities.

Abstract Deception Island fumaroles in Antarctica represent rare environments where extreme heat intersects with cryospheric and marine conditions, creating remarkable environmental gradients. From the near-boiling sediments, we reconstructed a high-quality metagenome-assembled genome (MAG) affiliated with the Pyrodictiaceae. Phylogenomic analyses revealed that this genome, proposed to represent Ca. Pyroantarcticum pellizari, forms a distinct lineage separated from known genera in the family. Functional annotation uncovered a versatile metabolic repertoire, including pathways for sulfur and nitrogen cycling, peptide and amino acid transport, and mixotrophic energy conservation. Stress-response systems such as reverse gyrase, thermosome, and small heat-shock proteins were complemented by lineage-specific genes related to membrane stability, metal detoxification, and Pyrodictiaceae-specific cannulae. These adaptations likely support survival under sharp temperature gradients, hydrogen sulfide emissions, and high metal concentrations at the volcanic–cryosphere–marine interface. Our findings expand the phylogenetic and ecological scope of Pyrodictiaceae, highlighting Antarctic marine volcanoes as unique refuges for hyperthermophiles and as valuable models for investigating life’s habitability under extreme temperatures.

Among citrus diseases, Huanglongbing (HLB) is recognized as the most destructive and economically damaging worldwide. It is mainly associated with ‘ Candidatus Liberibacter asiaticus’ ( C Las) being transmitted by Diaphorina citri . There are no curative treatments or commercial citrus varieties resistant to C Las. Wild Aurantioideae species have been widely screened and, recently, Oceanian genotypes graft- and sexually compatible with Citrus were identified as HLB-resistant; however, there is no information regarding their use as interstocks of commercial varieties yet. Under greenhouse conditions, six HLB-resistant genotypes were evaluated as interstocks between ‘Valencia’ sweet orange scion and ‘Rangpur’ lime rootstock, both susceptible to HLB, with ‘Valencia’ interstock as the control. Rootstocks were nucellar seedlings, and the scion was a commercial accession preimmunized with a mild CTV strain. Plants were assessed for C Las infection and titer in leaves, stem bark, and roots up to 12–24 months after graft-inoculation in the scion and compared to non-inoculated controls. Furthermore, molecular, anatomical, and biometric variables were investigated. As expected, the scion variety was colonized by C Las regardless of the genotype evaluated as interstock. Although bacteria were detected in the roots of most C Las-inoculated plants, C Las movement from the scion to the roots was blocked in 42% and 86% of composite plants when using a F1 hybrid of C. australis × C. inodora or an admixture hybrid of C. glauca , C. australis , and C. australasica as interstocks. Overall, C Las titers were similar in infected plant tissues among the evaluated genotypes, but titers were lower in interstock bark tissues compared to scion and rootstock ones. After one-two years of C Las + CTV infection (experiments I and II, respectively), the dry weight of the root system decreased by 50% in infected trees compared to control trees for most genotypes, and C Las + CTV infection was associated with changes in the sieve phloem and gene expression. These findings suggest that, despite CTV infection, interstocks derived from some hybrids of Australian citrus types have the potential to restrict the movement of C Las from the scion into the roots of infected citrus trees. Long-term evaluation of composite plants in field conditions is necessary to assess tree performance and, ultimately, the impact of C Las blockage by interstocking on HLB disease damage.