Control of canalization and evolvability by Hsp90.
Control of canalization and evolvability by Hsp90.
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DOI：
10.1371/journal.pone.0000075
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发表时间：
2006-12-20
期刊：
影响因子：
3.7
通讯作者：
Rutherford S
中科院分区：
文献类型：
--
作者：
Milton CC;Ulane CM;Rutherford S
部分减少的Hsp90增加表达的形态新奇性的质性状的果蝇和拟南芥，但在何种程度上的Hsp90伴侣也控制较小的，更可能的适应性变化的自然数量性状一直不清楚。为了确定热休克蛋白90对数量性状变异的影响，我们解构了遗传，随机和环境成分的变化，果蝇翅膀和刚毛性状的遗传匹配的苍蝇，不同的只有热休克蛋白90功能丧失或野生型等位基因。出乎意料的是，热休克蛋白90缓冲显着特定于某些正常不变和高度离散的数量性状。与Hsp90控制的质量性状表型一样，高度离散的数量性状如盾板和胸鬃数也是阈值性状。当从野生种群或实验室菌株中取样的基因型进行测试时，这些性状对许多类型的变异的敏感性是协调控制的，而连续可变的刚毛类型和翅膀大小，以及关键不变的左右翅膀不对称性，保持相对不受影响。虽然增加的环境变化和发展噪音会阻碍许多类型的选择反应，在重复的人口中，Hsp90是专门受损，遗传力和“外在的进化性”，预期的选择反应，也显着增加。然而，尽管热休克蛋白90对群体变异的总体缓冲作用，对于任何特定的个体或基因型，其中热休克蛋白90受损，其影响的大小和方向是不可预测的。Hsp90效应的性状和遗传背景依赖性及其对不变或渠道化性状的显著偏向支持了性状通过非线性和阈值的进化而进化独立和性状特异性的渠道化和可进化性机制的观点。高度非线性的反应将缓冲变化的热休克蛋白90依赖的信号在一个很宽的范围内，而在一个狭窄的范围内的信号特征阈值附近变得更加可变的触发全或无的发展反应的概率增加。
Partial reduction of Hsp90 increases expression of morphological novelty in qualitative traits of Drosophila and Arabidopsis, but the extent to which the Hsp90 chaperone also controls smaller and more likely adaptive changes in natural quantitative traits has been unclear. To determine the effect of Hsp90 on quantitative trait variability we deconstructed genetic, stochastic and environmental components of variation in Drosophila wing and bristle traits of genetically matched flies, differing only by Hsp90 loss-of-function or wild-type alleles. Unexpectedly, Hsp90 buffering was remarkably specific to certain normally invariant and highly discrete quantitative traits. Like the qualitative trait phenotypes controlled by Hsp90, highly discrete quantitative traits such as scutellor and thoracic bristle number are threshold traits. When tested across genotypes sampled from a wild population or in laboratory strains, the sensitivity of these traits to many types of variation was coordinately controlled, while continuously variable bristle types and wing size, and critically invariant left-right wing asymmetry, remained relatively unaffected. Although increased environmental variation and developmental noise would impede many types of selection response, in replicate populations in which Hsp90 was specifically impaired, heritability and ‘extrinsic evolvability’, the expected response to selection, were also markedly increased. However, despite the overall buffering effect of Hsp90 on variation in populations, for any particular individual or genotype in which Hsp90 was impaired, the size and direction of its effects were unpredictable. The trait and genetic-background dependence of Hsp90 effects and its remarkable bias toward invariant or canalized traits support the idea that traits evolve independent and trait-specific mechanisms of canalization and evolvability through their evolution of non-linearity and thresholds. Highly non-linear responses would buffer variation in Hsp90-dependent signaling over a wide range, while over a narrow range of signaling near trait thresholds become more variable with increasing probability of triggering all-or-none developmental responses.
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