Metarhizium brunneum Blastospore Pathogenesis in Aedes aegypti Larvae: Attack on Several Fronts Accelerates Mortality.
Metarhizium brunneum Blastospore Pathogenesis in Aedes aegypti Larvae: Attack on Several Fronts Accelerates Mortality.
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DOI：
10.1371/journal.ppat.1005715
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发表时间：
2016-07
期刊：
影响因子：
6.7
通讯作者：
Butt TM
中科院分区：
文献类型：
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作者：
Alkhaibari AM;Carolino AT;Yavasoglu SI;Maffeis T;Mattoso TC;Bull JC;Samuels RI;Butt TM
埃及伊蚊是多种疾病(如黄热病、登革热、基孔肯雅热和寨卡病毒)的媒介，影响着世界一半以上的人口。金龟子绿僵菌和球孢白僵菌等昆虫病原真菌对蚊子幼虫有很好的杀灭作用，但其致病机理目前尚不清楚。最近有研究表明，绿僵菌分生孢子可引起Ae的应激死亡。埃及伊蚊幼虫，一种与通常在陆地宿主中看到的不同的致病模式。当在液体介质中培养时，芽孢子构成了这种真菌产生的另一种接种形式，尽管芽孢子通常被认为比分生孢子更具毒性，但没有证据来解释为什么。本研究采用生化、分子和显微镜等多种方法，对绿僵菌ARSEF4556芽孢子的侵染过程进行了研究。看起来，与分生孢子不同，芽孢子很容易附着和穿透蚊子幼虫的角质层。芽孢子很容易被幼虫摄取，但与分生孢子不同的是，它能通过肠道感染昆虫，并迅速侵入血腔。在幼虫入侵之前，致病相关基因在胚芽孢子中表达上调，这表明该真菌正在检测寄主来源的线索。同样，免疫和防御基因在感染前在宿主中上调，这表明蚊子也能够检测到病原体衍生的线索。亲水性芽孢子产生丰富的粘液，这可能有助于与宿主的黏附，但似乎不依赖于PR1的产生，PR1是一种降解枯草杆菌蛋白酶的角质层，因为蛋白酶抑制剂不会显著改变芽孢子的毒力。胚芽孢子有多种进入途径(角质层和肠道)，这一事实可以解释为什么这种形式的接种剂会杀死Ae。埃及伊蚊幼虫在相对较短的时间内(12-24小时)，显著快于幼虫接触分生孢子。这项研究表明，选择合适的接种剂形式对于有效控制像Ae这样的病媒很重要。埃及伊蚊。蚊子传播一系列对人类健康有深远影响的疾病。埃及伊蚊传播登革热，这是出现速度最快的疾病之一，最近又传播了寨卡病毒，过去两年里，寨卡病毒与巴西数千例出生缺陷有关。昆虫病原真菌如绿僵菌对蚊虫成虫和幼虫有很好的杀灭作用。它们表现出很强的可塑性，在固体基质上产生气生分生孢子，在液体培养基中产生胚芽孢子。我们不仅证明了芽孢子比分生孢子更具毒性，而且提出了解释为什么它们更具侵袭性的证据。芽孢子的致病方式与分生孢子的致病方式有几个方面的不同。首先，胚芽孢子似乎更依赖于机械力的进入，而不是分泌角质层降解酶，如PR1。芽孢子产生丰富的粘液，确保许多孢子附着在角质层上。它们也很容易被摄取，并能够迅速穿透肠壁并在血腔内定植。多个入口点和对角质层和肠道的严重破坏会导致幼虫迅速死亡。分生孢子既不附着在角质层上，也不在肠道内萌发，但会导致PR1胁迫诱导的死亡，这需要稍长的时间。因此，Blastopore在控制Ae方面具有更大的潜力。埃及伊蚊幼虫在灭蚊计划中的应用
Aedes aegypti is the vector of a wide range of diseases (e.g. yellow fever, dengue, Chikungunya and Zika) which impact on over half the world’s population. Entomopathogenic fungi such as Metarhizium anisopliae and Beauveria bassiana have been found to be highly efficacious in killing mosquito larvae but only now are the underlying mechanisms for pathogenesis being elucidated. Recently it was shown that conidia of M. anisopliae caused stress induced mortality in Ae. aegypti larvae, a different mode of pathogenicity to that normally seen in terrestrial hosts. Blastospores constitute a different form of inoculum produced by this fungus when cultured in liquid media and although blastospores are generally considered to be more virulent than conidia no evidence has been presented to explain why. In our study, using a range of biochemical, molecular and microscopy methods, the infection process of Metarhizium brunneum (formerly M. anisopliae) ARSEF 4556 blastospores was investigated. It appears that the blastospores, unlike conidia, readily adhere to and penetrate mosquito larval cuticle. The blastospores are readily ingested by the larvae but unlike the conidia are able infect the insect through the gut and rapidly invade the haemocoel. The fact that pathogenicity related genes were upregulated in blastospores exposed to larvae prior to invasion, suggests the fungus was detecting host derived cues. Similarly, immune and defence genes were upregulated in the host prior to infection suggesting mosquitoes were also able to detect pathogen-derived cues. The hydrophilic blastospores produce copious mucilage, which probably facilitates adhesion to the host but do not appear to depend on production of Pr1, a cuticle degrading subtilisin protease, for penetration since protease inhibitors did not significantly alter blastospore virulence. The fact the blastospores have multiple routes of entry (cuticle and gut) may explain why this form of the inoculum killed Ae. aegypti larvae in a relatively short time (12-24hrs), significantly quicker than when larvae were exposed to conidia. This study shows that selecting the appropriate form of inoculum is important for efficacious control of disease vectors such as Ae. aegypti. Mosquitoes transmit a range of diseases which have a profound impact on human health. Aedes aegypti vectors dengue, one of the fastest emerging diseases and, more recently, the Zika virus, which has been linked to thousands of birth defects over the last two years in Brazil. Insect pathogenic fungi such as Metarhizium brunneum are effective in killing mosquito adults and larvae. They exhibit much plasticity, producing aerial conidia on solid substrates and blastospores in liquid media. We not only show that blastospores are more virulent than conidia but present evidence explaining why they are more aggressive. The blastospore mode of pathogenesis differs from that of conidia in several ways. Firstly, blastospores appear to be more dependent on entry using mechanical force than by secretion of cuticle degrading proteases such as Pr1. Blastospores produce copious mucilage which ensures that many spores attach to the cuticle. They are also readily ingested and able to penetrate the gut wall rapidly and colonize the haemocoel. Multiple entry points and gross damage to the cuticle and gut results in rapid larval death. Conidia neither adhere to the cuticle nor germinate in the gut but cause Pr1 stress induced mortality, which takes a slightly longer time. Blastopores, therefore, have greater potential for the control of Ae. aegypti larvae in mosquito control programmes
影响因子：
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作者：
Eastwood, Daniel C.;Mead, Andrew;Sergeant, Martin J.;Burton, Kerry S.
通讯作者：
Burton, Kerry S.