42,℃极端高温胁迫对木薯单爪螨（Mononychellus,mcgregori）保护酶及热激蛋白基因表达的影响

对照的5.19、4.38、152.23、321.42和3.41倍，且与其酶活性变化趋势存在一致性，酶活性值分别升高为对照的1.81、12.52、9.00、1.75和1.14倍。热激蛋白基因Hsp70的相对表达量显著升高，为对照的56.85倍。因此说明，保护酶POD、AsA-POD、CAT、SOD和PPO以及热激蛋白Hsp70可能在木薯单爪螨应对高温胁迫中具有重要作用，高温下保护酶及热激蛋白Hsp70基因表达量及其活性的升高可能导致木薯单爪螨对高温的耐受能力逐渐增强，从而逐渐适应热区高温环境，并可能增强其后续的繁殖能力而使其种群不断增长，扩张范围不断增强。

关键词 木薯单爪螨；高温；保护酶；热激蛋白；基因表达；酶活性

中图分类号 S533 文献标识码 A

Abstract Cassava green mite Mononychellus mcgregori is a newly invasive pest mite of cassava in China. It was reported the first time in Danzhou， Hainan， China in 2008 and has since become more widespread. The origin of M. mcgregori is South America and as a tropical native mite， the adaptation to high temperature is the significant foundation for its occurrence and damage. The results showed that the relative expression of PPO， POD， AsA-POD， CAT and Cu/Zn SOD genes in M. mcgregori via RTFQ PCR increased in adults after they were exposed to extremely high temperature（42 ℃）for 1 h， which increased 5.19， 4.38， 152.23， 321.42 and 3.41 times over that of the control， respectively， and were in accord with their enzyme activities（1.81， 12.52， 9.00， 1.75 and 1.14 times over that of the control）. And the relative expression of heat shock protein 70（Hsp70）gene increased 56.85 times over that of the control. These results suggested that protective enzymes POD， AsA-POD， CAT and SOD were associate with the thermostability of M. mcgregori and they might have synergistic effects on protect the mite against toxic oxygen intermediates and perhaps were associate with the resistance of high temperature in M. mcgregori. The increasing of PPO gene expression was perhaps associated with the immunity improvement of the mite to high temperature stress. And the elevated expression of Hsp70 gene was perhaps related to the adaptation of M. mcgregori to high temperature. These results provide a theoretical basis and precondition for further research on the molecular mechanisms of the thermostability and ecological adaptability of M. mcgregori.

Key words Mononychellus mcgregori； extreme high temperature； protective enzymes； heat shock protein； gene expression； enzyme activities

doi 10.3969/j.issn.1000-2561.2017.05.022

木薯单爪螨（Mononychellus mcgregori）原产地为南美洲，是一种热带土著害螨，对高温的适应性是其种群扩散的重要前提。该螨自2008年首次在中国海南发现，目前调查发现，其已在广西、广东、云南等省区广泛分布，且其发生期从入侵之初的仅在冬、春季发生而目前已发展到全年发生为害，已逐渐对中国发生区的气候环境产生适应。近年来该螨亦开始在泰国、柬埔寨和越南在内的亚洲国家木薯种植区扩散为害[1]。研究表明，木薯单爪螨对高温却相對敏感，36 ℃及以上高温胁迫1 h即可影响该螨的发育与繁殖，使其成螨产卵量减少，卵孵化率降低，42 ℃极端高温暴露1 h为木薯单爪螨热最敏感时间[2]。耐热性决定了昆虫的地理分布区域，研究表明，起源于热带及相对较干地区的昆虫种类具有更高的耐热性[3]。极端高温对昆虫种群地理分布、种群统计参数和种群增长、行为及种间关系等均存在显著影响[4-6]。赤足叶螨（Halotydeus destructor）在从南非入侵澳大利亚后，移动温度上限（HMT）和热昏迷温度（HCT）均显著升高，因此导致其在澳大利亚的地理分布范围扩大，并向更低维度地区扩散分布[7]。42 ℃高温处理4～6 h后，山楂叶螨成螨的产卵量和寿命均未受显著影响，39 ℃以上高温冲击会导致山楂叶螨种群数量迅速增加，这是导致山楂叶螨多在中国北方各地高温季节猖獗危害的直接诱因之一[8]。本研究对42 ℃极端高温胁迫1 h后木薯单爪螨各龄螨几种保护酶（PPO、POD、AsA-POD、CAT和SOD）基因表达与活性的差异以及热激蛋白Hsp70基因的表达做了分析，以探讨极端高温对木薯单爪螨的影响机制，为进一步研究其生态适应性及其机制，以及更好地监测其发生与扩散范围奠定基础。