Evidence that MRas1 and MRas3 proteins are associated with distinct cellular functions during growth and morphogenesis in the fungus Mucor racemosus.
Evidence that MRas1 and MRas3 proteins are associated with distinct cellular functions during growth and morphogenesis in the fungus Mucor racemosus.
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DOI：
10.1006/fgbi.1999.1177
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发表时间：
1999-12
期刊：
影响因子：
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通讯作者：
L. V. Roze;N. Mahanti;R. Mehigh;D. McConnell;John E. Linz
中科院分区：
文献类型：
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作者：
L. V. Roze;N. Mahanti;R. Mehigh;D. McConnell;John E. Linz
丝状真菌总状毛霉（Mucor racemosus）为研究与哺乳动物ras基因密切相关的基因家族中单个ras基因的功能提供了一个简单而独特的模型系统。本研究旨在探讨Mras 1和Mras 3在真菌形态发生不同阶段的作用，包括孢子囊孢子萌发，孢子形成，和二型转变。Mras 1和Mras 3转录和蛋白质积累的整体模式显着不同，但在一般情况下，转录和蛋白质是在低水平球形生长过程中，其积累水平增加了几倍，在极性生长（芽管出现和伸长）。与Mras 1相反，在孢子形成过程中积累了相对高水平的Mras 3转录本，并且Mras 3蛋白在孢子囊孢子中积累。转化M.总状花序与激活的Mras 3等位基因减少生长速率在有氧孢子囊孢子萌发，而显性负Mras 3等位基因造成了40%的减少，在可行的无性孢子。Mras 1的激活等位基因增加孢子囊孢子萌发过程中的生长速率，但既不激活也不显性负等位基因的Mras 1影响无性孢子的总数。Mras 3和Mras 1蛋白的表达似乎受到不同的调节机制：外源性二丁酰-cAMP和夫西二烯醇引起了强烈的Mras 3蛋白水平的抑制（但不是Mras 1）同时抑制极性生长。还观察到Mras 1和Mras 3蛋白的差异翻译后修饰和细胞内定位。这些数据有力地表明，Mras 3和Mras 1在毛霉的细胞生长和形态发生的调节中发挥不同的作用。
The filamentous fungus Mucor racemosus provides a simple and unique model system for defining the function of individual ras genes in a gene family which is closely related to mammalian ras genes. The current study was designed to investigate the role of Mras1 and Mras3 in different stages of fungal morphogenesis, including sporangiospore germination, sporulation, and dimorphic transitions. The overall patterns of Mras1 and Mras3 transcript and protein accumulation were markedly different but, in general, transcripts and proteins were present at low levels during spherical growth and their accumulated level increased severalfold during polar growth (germ tube emergence and elongation). In contrast to Mras1, relatively high levels of Mras3 transcript accumulated during sporulation and MRas3 protein accumulated in sporangiospores. Transformation of M. racemosus with an activated allele of Mras3 reduced growth rate during aerobic sporangiospore germination, while a dominant-negative allele of Mras3 caused a 40% decrease in viable asexual spores. An activated allele of Mras1 increased growth rate during sporangiospore germination but neither activated nor dominant-negative alleles of Mras1 affected total number of asexual spores. Expression of MRas3 and MRas1 proteins appear to be subject to different regulatory mechanisms: exogenous dibutyryl-cAMP and fusidienol caused a strong repression of the level of MRas3 protein (but not MRas1) concurrent with the inhibition of polar growth. Differential posttranslational modification and intracellular localization of MRas1 and MRas3 proteins were also observed. The data strongly suggest that Mras3 and Mras1 play different roles in regulation of cell growth and morphogenesis in Mucor.