Vereecke Danny, Zhang Yucheng, Francis Isolde M, Lambert Paul Q, Venneman Jolien, Stamler Rio A, Kilcrease James, Randall Jennifer J
Entomology, Plant Pathology, and Weed Science, New Mexico State University, Las Cruces, NM, United States.
Department of Plant Pathology, University of Florida, Gainesville, FL, United States.
Front Microbiol. 2020 Jan 30;11:14. doi: 10.3389/fmicb.2020.00014. eCollection 2020.
Pistachio Bushy Top Syndrome (PBTS) is a recently emerged disease that has strongly impacted the pistachio industry in California, Arizona, and New Mexico. The disease is caused by two bacteria, designated PBTS1 that is related to and PBTS2 that belongs to the species . Here, we assessed the pathogenic character of the causative agents and examined their chromosomal sequences to predict the presence of particular functions that might contribute to the observed co-occurrence and their effect on plant hosts. In diverse assays, we confirmed the pathogenicity of the strains on "UCB-1" pistachio rootstock and showed that they can also impact the development of tobacco species, but concurrently inconsistencies in the ability to induce symptoms were revealed. We additionally evidence that genes are present only in a subpopulation of pure PBTS1 and PBTS2 cultures after growth on synthetic media, that these genes are easily lost upon cultivation in rich media, and that they are enriched for in an environment. Analysis of the chromosomal sequences indicated that PBTS1 and PBTS2 might have complementary activities that would support niche partitioning. Growth experiments showed that the nutrient utilization pattern of both PBTS bacteria was not identical, thus avoiding co-inhabitant competition. PBTS2 appeared to have the potential to positively affect the habitat fitness of PBTS1 by improving its resistance against increased concentrations of copper and penicillins. Finally, mining the chromosomes of PBTS1 and PBTS2 suggested that the bacteria could produce cytokinins, auxins, and plant growth-stimulating volatiles and that PBTS2 might interfere with ethylene levels, in support of their impact on plant development. Subsequent experimentation supported these predictions. Altogether, our data provide an explanation for the observed pathogenic behavior and unveil part of the strategies used by PBTS1 and PBTS2 to interact with plants.
阿月浑子丛顶综合征（PBTS）是一种最近出现的疾病，对加利福尼亚州、亚利桑那州和新墨西哥州的阿月浑子产业造成了严重影响。该疾病由两种细菌引起，分别命名为与 相关的PBTS1和属于 物种的PBTS2。在此，我们评估了病原体的致病特性，并检查了它们的染色体序列，以预测可能有助于观察到的共存现象的特定功能及其对植物宿主的影响。在各种试验中，我们证实了这些菌株对“UCB - 1”阿月浑子砧木的致病性，并表明它们也会影响烟草品种的发育，但同时也发现了诱导症状能力的不一致性。我们还证明，在合成培养基上生长后， 基因仅存在于纯PBTS1和PBTS2培养物的一个亚群中，这些基因在丰富培养基中培养时很容易丢失，并且在 环境中会富集。染色体序列分析表明，PBTS1和PBTS2可能具有互补活性，这将支持生态位划分。生长实验表明，两种PBTS细菌的养分利用模式并不相同，从而避免了共同栖息者之间的竞争。PBTS2似乎有可能通过提高PBTS1对铜和青霉素浓度增加的抗性来积极影响其栖息地适应性。最后，对PBTS1和PBTS2染色体的挖掘表明，这些细菌可以产生细胞分裂素、生长素和刺激植物生长的挥发物，并且PBTS2可能会干扰乙烯水平，以支持它们对植物发育的影响。随后的实验支持了这些预测。总之，我们的数据为观察到的数据提供了解释，并揭示了PBTS1和PBTS2与植物相互作用所使用的部分策略。
