Publications

4512

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 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.

ABSTRACT We report the draft metagenome-assembled genome (MAG) of “ Candidatus Phytoplasma australasiaticum” strain TBB-AP, obtained from a symptomatic tomato plant collected in Andhra Pradesh, India. This assembly provides a genomic resource for functional and evolutionary studies of phytoplasmas associated with tomato big bud disease.

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.