Publications

4467

Abstract Background ‘ Candidatus Liberibacter solanacearum’ (Lso) is a phloem-limited bacterial pathogen causing significant diseases in solanaceous crops. In the United States, haplotypes A and B are transmitted by the potato psyllid Bactericera cockerelli . We previously identified differences in their acquisition and transmission between adults and nymphs. The present study characterized the dynamics of LsoA and LsoB acquisition and transmission by nymphs and examined the transcriptional responses of the nymphal gut upon their acquisition. Methods and results Nymphs were exposed to LsoA- or LsoB-infected plants for 1, 3, 5, or 7 days to measure the bacterial accumulation and for 8 days to assess the transmission efficiency following sequential inoculation of tomato plants. Quantitative PCR showed that LsoB accumulated to higher levels than LsoA after 3 days of acquisition. Following the sequential inoculation, LsoB was transmitted earlier than LsoA indicating a shorter latency period. RNA-seq analysis of the guts following a 1- and 5-day acquisition access periods revealed a greater transcriptional regulation at 5 days than at 1 day. Furthermore, the responses were haplotype-specific: LsoA primarily affected genes involved in protein translation, ER stress, and cell cycle regulation, whereas LsoB regulated genes involved in autophagy, apoptosis, and immune pathways. Conclusions This study revealed haplotype-specific gene regulation potentially leading to LsoB being transmitted more efficiently by psyllid nymphs.

Abstract ‘Candidatus Mycoplasma haemolamae’ (CMhl) is a hemotropic bacterium infecting South American Camelids (SAC), whose epidemiology and clinical significance are still not fully elucidated. This study investigated CMhl by qPCR in blood samples of alpacas ( Vicugna pacos ) and llamas ( Lama glama ) in Italy in 2021–2024, characterizing CMhl haplotypes based on partial 16 S rRNA sequences and defining haematological findings in a subset of CMhl-infected animals. Statistical analysis was performed to detect potential risk factors associated with CMhl positivity. Out of 206 animals (200 alpacas and 6 llamas), CMhl was detected by qPCR in 88 (42.7%) animals. CMhl haplotype #1 and #2 were detected in 42.2% and 0.5% of the animals, respectively. Binary logistic regression analysis showed that higher CMhl positivity was significantly associated with larger herd size ( P  = 0.011), Northern Italy area of origin ( P  = 0.031) and warmer seasons ( P  = 0.003). The detection of two CMhl haplotypes confirms the high diffusion of CMhl in SAC farmed in Italy. Results confirm that CMhl usually causes subclinical infections, suggesting that antimicrobial treatment is likely not necessary based on qPCR positivity alone. Results focusing on the association of CMhl positivity with warm temperatures and large herd size suggest the need of further studies on the genetic features, epidemiology and immune response in CMhl-positive SAC from Italy, with emphasis on understanding potential vector transmission.

ABSTRACT Cable bacteria conduct long-distance electron transport in sediments but are not yet isolated in pure culture. We report the metagenome-assembled genome of Candidatus Electrothrix sp. NPCB-01 from Newport Bay, California. This 3.46-Mb genome encodes sulfur oxidation, nitrogen and carbon metabolism, and nickel homeostasis genes, expanding resources for these electroactive microbes.

Welsh onion (Allium fistulosum) is an important aromatic vegetable crop, particularly in Asia (Kim et al. 2023). In November 2025, two-month-old Welsh onion plants showing leaf proliferation, little leaf, and yellowing symptoms were found at low frequency (< 1%) in Fangyuan Township, Changhua County, Taiwan. The plot was around 880 m 2 in size and about 7,200 clumps were grown. Five symptomatic and three symptomless plants were sampled (bagged separately). The plants’ basal leaf tissues were subjected to DNA extraction and PCR analysis. DNA was extracted using a Synergy 2.0 Plant DNA Extraction Kit (OPS Diagnostics) using filter tips, and the DNA samples’ quality was verified by successful amplification of a plant 26S rDNA fragment (0.7 kb) using primer pair 28KJ/28C (Cullings 1992). Nested polymerase chain reaction (PCR) assays using phytoplasma 16S rDNA-specific primers were conducted. The nested primer pairs used were P1/P7 and fU5/rU3 (Lorenz et al. 1995), respectively. DNA of periwinkle infected with periwinkle leaf yellowing phytoplasma served as a positive control and no-template controls (nuclease-free water) were included in both PCR rounds. In both tests, only DNA from the five symptomatic plants produced the expected amplicons (1.8 kb and 881 bp for the outer and inner assays). The products from the first and second rounds of PCR were sequenced and assembled. Sequencing chromatograms of the PCR products had single, well-resolved peaks across all positions in all the samples, indicating that only one strain was present. Near-full-length (1,466 bp) 16S rDNA sequences of all five samples were identical to that of a reference ‘Candidatus Phytoplasma australasiaticum’-related strain, NCHU2014 (accession no. CP040925, bp 537,765 to 539,230; 16SrII-A; Rodrigues Jardim et al. 2023), and a representative sequence has been deposited in GenBank (accession no. PX696818). A 1,248 bp fragment (accession no. PX696818, bp 84 to 1,331) of the detected 16S rDNA sequence was excised for analysis using the web tool iPhyClassifier (https://plantpathology.ba.ars.usda.gov/cgi-bin/resource/iphyclassifier.cgi), and the virtual RFLP patterns obtained were identical to the reference pattern of 16SrII-A (accession no. L33765; similarity coefficient 1.00). Additional PCR tests targeting the protein translocase gene secY and the elongation factor Tu gene (tuf) of 16SrII phytoplasmas were respectively conducted with the infected samples using primer pairs SecYF1(II)/SecYR1(II) and TUF-II-F1/TUF-II-R1 (Al-Subhi et al. 2017; Lee et al. 2010). The secY (accession no. PX737873; 1,263 bp) and tuf (accession no. PX737874; 1,183 bp) sequences were again found identical to those of the reference strain NCHU2014 (16SrII-A phytoplasma; accession no. CP040925, bp 192,846 to 194,108 and bp 139,150 to 140,332). In Taiwan, 16SrII phytoplasma has been reported affecting various plants, such as seseme and purple coneflower (Rodrigues Jardim et al. 2023; Tseng et al. 2014). In A. fistulosum, however, phytoplasma infection has only been associated with group 16SrI (Cho et al. 2019). The present study is the first report of a 16SrII-A phytoplasma affecting Welsh onion and the findings expand the understanding of the width of the subgroup’s host range in the island. Since Welsh onion is an important culinary crop, and the disease significantly affects its morphology and commercial value, ongoing surveillance of its spread in other regions is warranted.