Growth and macromolecular synthesis phenotypes of a heat-sensitive mutant strain, rip-1, of Neurospora crassa.
Growth and macromolecular synthesis phenotypes of a heat-sensitive mutant strain, rip-1, of Neurospora crassa.
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粗糙脉孢菌热敏突变株 rip-1 的生长和大分子合成表型。
DOI：
10.1007/bf00425431
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发表时间：
1985
期刊：
影响因子：
--
通讯作者：
Schricker,NS
中科院分区：
文献类型：
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作者：
Russell,PJ;Loo,MW;Schricker,NS
采用紫外诱变-无肌醇死亡富集技术分离了一株粗神经孢子虫（neurospora crassa）的热敏突变株4M(t)。热敏性是单一基因突变的结果，该突变位于连锁组II右臂的远端。该突变定义了ip-1基因位点。突变体的分生孢子萌发和菌丝伸展在35°C及以上（非允许温度）时都受到抑制，但在该温度下长时间孵育对两种细胞类型都不致命。对野生型和therip-1突变体在10 ~ 40℃不同温度下菌丝生长速率的分析表明，野生型在35℃时菌丝生长速率最大，而therip-1突变体在25℃时菌丝生长速率最大。therip -1突变体在35°C下的生长速度比在25°C下慢239倍，而野生型的生长速度快1.4倍。温度升高实验表明，即使在20℃下3 h也不足以在37℃下发芽，从而表明突变体不能在允许温度下积累足够的热敏产物来促进37℃下的萌发。倒数温度下移实验表明，37℃时的分子事件在转移到20℃后可能对萌发有定性作用。大分子合成研究表明，热敏菌株的生化缺陷似乎先于蛋白质合成影响RNA合成，尽管根据萌发分生孢子的年龄存在相对影响差异，并且这两个过程的抑制从未完成。在37℃下，突变体的信使RNA合成正常。先前的研究表明，ip-1突变株在25S rRNA的积累方面存在条件缺陷，因此在60S核糖体亚基的产生方面存在缺陷（Loo et al. 1981）。这些研究也表明，60S核糖体亚基可能在较高温度下功能受损。因此，生长和大分子合成表型可能是条件核糖体功能缺陷的结果，并导致假设therip-1菌株的突变可能发生在60S核糖体亚基成分的基因中，可能是核糖体蛋白。
A heat-sensitive mutant ofNeurospora crassa, strain 4M(t), was isolated using ultraviolet-light mutagenesis followed by the inositol-less death enrichment technique. The heat-sensitivity is the result of a single gene mutation which maps to the distal end of the right arm of linkage group II. The mutation defines therip-1gene locus. Both conidial germination and mycelial extension are inhibited in the mutant at 35°C and above (the nonpermissive temperature) but prolonged incubation at that temperature is not lethal to either cell type. Analysis of the lateral mycelial growth rates of wild type and of therip-1mutant at a variety of temperatures between 10 and 40°C indicated that the maximal growth rate occurs at 35°C in the wild type, and at 25°C in therip-1strain. Therip-1mutant grows 239-times slower at 35°C than at 25°C, whereas the wild type grows 1.4-times faster. Temperature shift-up experiments showed that even 3 h at 20°C is not sufficient to allow germination at 37°C, thereby showing that the mutant cannot accumulate enough heat-sensitive product at the permissive temperature to contribute to germination at 37°C. The reciprocal temperature shift-down experiments showed that the molecular events at 37°C may be qualitatively useful for germination after shifting to 20°C. Studies of macromolecular synthesis showed that the biochemical defect in the heat-sensitive strain appears to affect RNA synthesis before protein synthesis, although there were differences in the relative effects depending on the age of the germinating conidia and the inhibition of the two processes was never complete. Messenger RNA synthesis is normal in the mutant at 37°C. Previous work has shown that therip-1mutant strain has a conditional defect in the accumulation of 25S rRNA and, hence, in 60S ribosomal subunit production (Loo et al. 1981). There are also indications from those studies that the 60S ribosomal subunit may be functionally impaired at the higher temperature. Thus, the growth and macromolecular synthesis phenotypes may result as a consequence of a conditional, ribosome function defect and leads to the hypothesis that the mutation in therip-1strain may be in a gene for a 60S ribosomal subunit component, perhaps a ribosomal protein.