Acquisition, Replication and Inoculation of Candidatus Liberibacter asiaticus following Various Acquisition Periods on Huanglongbing-Infected Citrus by Nymphs and Adults of the Asian Citrus Psyllid.
Acquisition, Replication and Inoculation of Candidatus Liberibacter asiaticus following Various Acquisition Periods on Huanglongbing-Infected Citrus by Nymphs and Adults of the Asian Citrus Psyllid.
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DOI：
10.1371/journal.pone.0159594
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发表时间：
2016
期刊：
影响因子：
3.7
通讯作者：
Shatters RG Jr
中科院分区：
文献类型：
--
作者：
Ammar el-D;Ramos JE;Hall DG;Dawson WO;Shatters RG Jr
柑桔木虱Diaphorina citri（半翅目：木虱科）是柑桔黄龙病（Citrus huanglongbing，简称黄龙病）的主要传播媒介。Las由D. Citri以持续循环的方式，但这种细菌在其木虱载体中复制的问题尚未解决。因此，我们研究了获得访问期（AAP）的影响，由杜父鱼和成年人。柑桔对Las的获得、增殖和接种/传播的影响。D.将柑橘属害虫或成虫（先前未暴露于LAS）关在LAS感染的柑橘植物上，AAP为1、7或14天。然后每周将这些“Las-exposed”木虱转移到健康的柑橘或橙子茉莉植物上，并在第一次接触患病植物（padp）后1-42天通过定量聚合酶链反应（qPCR）分析取样;所有测试的木虱在padp 7-14天变成成虫。我们的结果表明，在1或7天的AAP后，49-59%的Las-exposed木虱变成Las-infected（qPCR-阳性），而在1-14天的AAP后，只有8-29%的木虱作为成虫被感染。Q-PCR分析还表明，在激光暴露的木虱中，（相对于木虱S20核糖体蛋白基因的）：（1）与成虫相比，以成虫获得Las后，以更快的速度获得Las后，显著增加;（2）木虱在健康植株上的取食时间越长，其取食量越高，在14-28天达到高峰，成虫在21-35天达到高峰，在此之后，Las滴度下降或波动; 3）在感染的植物上，特别是在作为成虫获得的情况下，随着AAP时间的延长而升高。我们的研究结果强烈地表明，Las在D.柑橘，但达到高得多的水平在较短的时间内收购后收购时，收购时比收购时的成年人，成年人可能需要更长的访问受感染的植物相比，收购后的时间为Las在载体中达到更高的水平。然而，在我们的实验条件下，只有D。能够接触到受感染植物的柑橘能够将Las转化为健康的柑橘幼苗或切除的叶子。我们和其他人报道，当木虱在若虫阶段而不是成虫阶段从受感染的植物中获得这种细菌时，Las接种到柑橘中的可能性更高，这在经济上重要的柑橘疾病的流行病学和控制中具有重要意义。
The Asian citrus psyllid, Diaphorina citri (Hemiptera: Liviidae), is the primary vector of Candidatus Liberibacter asiaticus (Las) implicated as causative agent of citrus huanglongbing (citrus greening), currently the most serious citrus disease worldwide. Las is transmitted by D. citri in a persistent-circulative manner, but the question of replication of this bacterium in its psyllid vector has not been resolved. Thus, we studied the effects of the acquisition access period (AAP) by nymphs and adults of D. citri on Las acquisition, multiplication and inoculation/transmission. D. citri nymphs or adults (previously non-exposed to Las) were caged on Las-infected citrus plants for an AAP of 1, 7 or 14 days. These ‘Las-exposed’ psyllids were then transferred weekly to healthy citrus or orange jasmine plants, and sampled via quantitative polymerase chain reaction (qPCR) analysis 1–42 days post-first access to diseased plants (padp); all tested nymphs became adults 7–14 days padp. Our results indicate that following 1 or 7 day AAP as nymphs 49–59% of Las-exposed psyllids became Las-infected (qPCR-positive), whereas only 8–29% of the psyllids were infected following 1–14 day AAP as adults. Q-PCR analysis also indicated that Las titer in the Las-exposed psyllids (relative to that of the psyllid S20 ribosomal protein gene) was: 1) significantly higher, and increasing at a faster rate, following Las acquisition as nymphs compared to that following Las acquisition as adults; 2) higher as post-acquisition time of psyllids on healthy plants increased reaching a peak at 14–28 days padp for nymphs and 21–35 days padp for adults, with Las titer decreasing or fluctuating after that; 3) higher with longer AAP on infected plants, especially with acquisition as adults. Our results strongly suggest that Las multiplies in both nymphs and adults of D. citri but attains much higher levels in a shorter period of time post-acquisition when acquired by nymphs than when acquired by adults, and that adults may require longer access to infected plants compared to nymphs for Las to reach higher levels in the vector. However, under the conditions of our experiments, only D. citri that had access to infected plants as nymphs were able to inoculate Las into healthy citrus seedlings or excised leaves. The higher probability of Las inoculation into citrus by psyllids when they have acquired this bacterium from infected plants during the nymphal rather than the adult stage, as reported by us and others, has significant implications in the epidemiology and control of this economically important citrus disease.