ARO, The Volcani Center, P.O.B. 6, Bet-Dagan 50250, Israel.
J Invertebr Pathol. 2010 Feb;103(2):132-9. doi: 10.1016/j.jip.2009.12.010. Epub 2009 Dec 29.
Conidial germination and the formation of appressoria are important events in the interactions between entomopathogenic fungi and their arthropod hosts. In this study, we demonstrate the effects of lipids extracted from tick epicuticle and the surface of a mammalian host (calf) on conidial germination and the development of appressoria in two subspecies of Metarhizium anisopliae, M. anisopliae var. anisopliae (M.an.an.-7) and M. anisopliae var. acridum (M.an.ac.-5), which have different levels of virulence toward ticks. Pentane extracts of epicuticles of ticks susceptible and resistant to fungal infection always stimulated the germination of M.an.an.-7 conidia and the development of their appressoria; whereas the effects of dichloromethane (DCM) extracts of tick epicuticle varied depending on the tick. The DCM extracts from most of the tick species and developmental stages stimulated conidial germination and/or the formation of appressoria in M.an.an.-7. However, a DCM extract of lipids from the most resistant tick, engorged Hyalomma excavatum female, inhibited the germination of M.an.an.-7 conidia. Conidia of the non-virulent M.an.ac.-5 did not germinate on agarose amended with any of the examined tick extracts. However, when the tick extracts were placed on bactoagar, conidial germination increased 7- to 8-fold. Extracts from the skin, hair and ear secretions of a calf stimulated conidial germination and the formation of appressoria in M.an.an.-7, but not M.an.ac.-5. This study demonstrates that lipids from tick epicuticles and mammalian skin selectively affect the germination of conidia of entomopathogenic fungi. The effects of these lipids may explain the variability in tick control these fungi provide for different hosts.
分生孢子的萌发和附着胞的形成是昆虫病原真菌与其节肢动物宿主相互作用的重要事件。在这项研究中，我们展示了从蜱的表皮和哺乳动物宿主（小牛）表面提取的脂质对两种绿僵菌亚种（绿僵菌 var. anisopliae（M.an.an.-7）和绿僵菌 var. acridum（M.an.ac.-5）的分生孢子萌发和附着胞发育的影响，这两种亚种对蜱具有不同的毒力。易受真菌感染的蜱的表皮的戊烷提取物总是刺激 M.an.an.-7分生孢子的萌发和附着胞的发育；而蜱表皮二氯甲烷（DCM）提取物的影响则取决于蜱的种类。来自大多数蜱种和发育阶段的 DCM 提取物刺激 M.an.an.-7 分生孢子的萌发和/或附着胞的形成。然而，最具抗性的蜱，饱血的 H.excavatum 雌性的 DCM 脂质提取物抑制了 M.an.an.-7 分生孢子的萌发。非致病的 M.an.ac.-5 的分生孢子不会在添加了任何检查过的蜱提取物的琼脂糖上萌发。然而，当将蜱提取物置于细菌琼脂上时，分生孢子的萌发增加了 7-8 倍。来自小牛皮肤、毛发和耳分泌物的提取物刺激 M.an.an.-7 分生孢子的萌发和附着胞的形成，但不刺激 M.an.ac.-5。本研究表明，蜱表皮和哺乳动物皮肤中的脂质选择性地影响昆虫病原真菌分生孢子的萌发。这些脂质的作用可能解释了这些真菌对不同宿主提供的蜱控制的可变性。
