Evaluating physical and nutritional stress during mycelial growth as inducers of tolerance to heat and UV-B radiation in Metarhizium anisopliae conidia
Evaluating physical and nutritional stress during mycelial growth as inducers of tolerance to heat and UV-B radiation in Metarhizium anisopliae conidia
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DOI：
10.1016/j.mycres.2008.04.013
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发表时间：
2008-11-01
影响因子：
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通讯作者：
Roberts, Donald W.
中科院分区：
文献类型：
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作者：
Rangel, Drauzio E. N.;Anderson, Anne J.;Roberts, Donald W.
在菌丝体生长过程中暴露于菌丝的真菌中，可能会诱发对UV-B辐射的耐受性和热量的耐受性。这是由于一种称为“交叉保护”的现象。几种机制与增加的分生孢子耐受性有关，其中一种机制是分生孢子内海藻糖和甘露醇的积累。在本研究中，昆虫性真菌元雄性动物的分生孢子。在菌丝体上产生各有营养，热震，渗透或氧化应激。评估了对压力菌丝体的分生孢子对UV-B辐射的公差水平，并对分生孢子中积累的海藻糖和甘露醇的量进行了评估。在营养应激（碳和氮饥饿）下产生的分生孢子比在富含（非压力）营养条件下产生的分生孢子（用酵母提取物（Pday）产生的分生孢子）要高两次，并且它们也积累了最高的Trehalose和Mannitol浓度。与没有热休克产生的分生孢子相比，在热震压力上产生的分生孢子对UV-B辐射和热的耐受性更高。然而，在热菌丝菌丝体上产生的分生孢子中的UV-B耐受性和海藻糖/甘露糖浆浓度都低于在营养应激下产生的分生孢子。在渗透应激（添加到Pday中添加的氯化钠或氯化钾）下产生的分生孢子具有升高的热量和UV-B耐受性，类似于在营养应激下产生的分生孢子。但是，它们具有最低水平的甘露醇和海藻糖，这表明这些化合物的积累并不是弧菌支原体用于保护热和UV-B辐射的唯一机制。 UV-A辐射或过氧化氢的氧化应激不会产生UV-B或耐热性升高的分生孢子。在甲二烯产生的氧化应激下产生的分生孢子分别增加或不变的热或UV-B耐受性。分生孢子中的甘露醇或黄盐水平与无重大对照中的水平相似。在某些情况下，通过营养和渗透应激严重降低了分生孢子产量。而氧化和热震动力不会改变孢子的产生水平。 （c）2008年英国真菌学会。由Elsevier Ltd.出版。保留所有权利。
Elevated tolerance to UV-B radiation and heat may be induced in conidia produced on fungi exposed during mycelial growth to sublethal stresses other than heat or UV-B. This is due to a phenomenon referred to as 'cross-protection'. Several mechanisms are associated with this increased conidial tolerance, one of which is the accumulation of trehalose and mannitol within conidia. In the present study, conidia of the insect-pathogenic fungus Metarhizium anisopliae var. anisopliae were produced on mycelium subjected to nutritive, heat-shock, osmotic, or oxidative stress. The tolerance levels to UV-B radiation and heat of the conidia from stressed mycelium were evaluated, and the amounts of trehalose and mannitol accumulated in conidia were quantified. Conidia produced under nutritive stress (carbon and nitrogen starvation) were two-times more heat and UV-B tolerant than conidia produced under rich (non-stress) nutrient conditions [potato-dextrose agar with yeast extract (PDAY)], and they also accumulated the highest concentrations of trehalose and mannitol. Conidia produced on heat-shock stressed PDAY cultures had higher tolerance to UV-B radiation and heat than conidia produced without heat shock; however, both the UV-B tolerance and trehalose/mannitol concentrations in conidia produced on heat-shocked mycelium were less than those of conidia produced under nutritive stress. Conidia produced under osmotic stress (sodium or potassium chloride added to PDAY) had elevated heat and UV-B tolerances similar to those of conidia produced under nutritive stress; however, they had the lowest levels of mannitol and trehalose, which indicates that accumulation of these compounds is not the only mechanism used by M. anisopliae for protection from heat and UV-B radiation. Oxidative stress from UV-A irradiation or hydrogen peroxide did not produce conidia with elevated UV-B or heat tolerances. Conidia produced under oxidative stress generated by menadione had increased or unchanged tolerances to heat or UV-B, respectively. The levels of mannitol or trehalose in conidia were similar to those in the unstressed controls. Conidial yield was reduced, in some cases severely, by nutritive and osmotic stress; whereas oxidative and heat-shock stress did not alter levels of spore production. (C) 2008 The British Mycological Society. Published by Elsevier Ltd. All rights reserved.