MAPK信号通路与转录因子Cmr在沙漠酵母菌黑色素合成调控中的作用研究

The Taklimakan desert is the largest desert in China and it has been regarded as ‘‘Dead Sea’’ because of its harsh environments. Our previous study found that a yeast strain Aureobasdium melanogenum XJ5-1 isolated from the Taklimakan desert could produce a large amount of melanin in its cells and the produced melanin could play an important role in the stress adaptation of XJ5-1 cells. So far, PKS and other enzymes have been found to be involved in melanin biosynthesis. However, it is still a little known about melanin regulation at molecular levels. Furthermore, the correlations between adverse environmental signals, signaling pathway and melanin biosynthesis in the desert yeasts have not been fully understood. In this project, the roles of the MAPK signaling pathways and the transcription factor Cmr in melanin biosynthesis and regulation of the desert yeast A. melanogenum XJ5-1 will be investigated. The goal of this project is to explore the relationship between adverse environmental signals, MAPK signaling pathways and melanin biosynthesis. First, the role of transcription activator Cmr in melanin biosynthesis and regulation will be elucidated. Second, the perception of adverse environmental signals by the receptors from the MAPK signaling pathways will be investigated and effect of the perception of adverse environmental signals on melanin biosynthesis will be examined. Finally, the studies on the transcription of the CMR1 gene and the genes including the PKS1 involved in melanin biosynthesis under the control of the transcriptional factors from the MAPK signaling pathways will be carried out. This study will be of significant for insights into stress adaptation mechanisms of the desert yeasts.

塔克拉玛干沙漠是中国最大的沙漠，其条件极端恶劣一度被称为“死海”。我们前期研究结果表明，黑色素在沙漠酵母菌XJ5-1菌株抵抗塔克拉玛干沙漠极端环境中发挥了重要的作用。但沙漠酵母菌如何感知极端的环境信号，并在分子水平上调控黑色素等抗逆物质的合成来抵抗极端环境呢？在前期工作基础上，本申请项目主要开展MAPK信号通路与转录因子Cmr对XJ5-1菌株黑色素的合成调控作用研究。以沙漠酵母菌XJ5-1菌株为材料，首先开展转录激活因子Cmr通过调控黑色素合成基因转录来调控黑色素合成的研究；然后进行MAPK信号通路受体蛋白感受极端环境信号并影响黑色素合成的研究；最后研究MAPK信号通路转录因子通过调控CMR1基因与黑色素合成基因转录来调控黑色素的合成。以期获得极端环境信号、MAPK信号通路与抗逆物质黑色素合成调控之间的关系。研究结果对进一步了解沙漠酵母菌的极端环境适应机制具有重要的意义。

塔克拉玛干沙漠是中国最大的沙漠，其条件极端恶劣一度被称为“死海”。我们前期研究结果表明，黑色素在沙漠酵母菌XJ5-1菌株抵抗塔克拉玛干沙漠极端环境中发挥了重要的作用。但沙漠酵母菌如何通过信号通路感知极端的环境信号，并在分子水平上调控黑色素等抗逆物质的合成来抵抗极端环境呢？在前期工作基础上，本申请项目沙漠酵母菌Aureobasidium melanogenum XJ5-1菌株为材料，通过基因敲除与回补实验主要开展MAPK信号通路与转录因子Cmr对XJ5-1菌株黑色素的合成调控作用研究。发现细胞壁完整型（Cell Wall Integrity，CWI）MAPK信号通路中激酶Slt2可以调控转录激活因子Swi4的活性；反过来，Swi4可以控制特异性转录激活因子Cmr1基因的表达。Cmr1的DNA结合域（DNA-binding domain，DBD）能特异性识别PKS1基因启动子中的TTCTCTCCA序列并与之特异性结合，激活PKS1基因及其他负责黑色素生物合成相关基因的表达，从而使沙漠酵母菌能够A. melanogenum XJ5-1能够产生大量的黑色素。因此，与其他真菌不同，CWI型MAPK信号通路会通过转录激活因子Cmr调控沙漠酵母菌能够A. melanogenum XJ5-1黑色素的合成。这为进一步研究沙漠酵母对恶劣环境的感知、响应和适应提供了基础。此外，还分别探究了产黑色素短梗霉类酵母菌A. melanogenum在普鲁兰多糖合成及低聚果糖中转化中的应用。研究结果不仅对进一步了解沙漠酵母菌的极端环境适应机制具有重要的意义，也为更好的开利用产黑色素短梗霉类酵母菌奠定了基础。

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