科研人员在测试新型DNA测序技术时意外发现了一种名为Oligohymenophorea sp. PL0344的微生物，其遗传密码系统违反了被普遍认为是生命通用法则的规则1。在这种微生物中，两个通常标记基因终止信号的遗传信号TAA和TAG被重新编码为两种不同的氨基酸——TAA编码赖氨酸，TAG编码谷氨酸——而不是像其他已知生物那样执行相同功能1。
参与研究的Earlham Institute和University of Oxford的科研团队随后对其他纤毛虫物种进行了调查，发现这种遗传密码的灵活性在微生物中比预期更为广泛1。研究者Dr. McGowan指出："在我们已知的几乎所有其他情况下，TAA和TAG会一起改变。当它们不是停止密码子时，它们各自指定相同的氨基酸"1。在至少5种其他纤毛虫物种中，科学家发现了UAG被独立地重新编码为亮氨酸或谷氨酰胺的案例1。该发现最初于2023年10月在《PLOS Genetics》上发表1。
Researchers accidentally uncovered a microorganism with a genetic code that violates the long-held principle that the genetic code is universal across all life.1 While testing new DNA sequencing technology, scientists identified a ciliate species called Oligohymenophorea sp. PL0344, in which two genetic signals normally reserved for marking the end of genes have been reassigned to encode amino acids instead.1
Specifically, the stop codons TAA and TAG—which should signal the termination of protein synthesis—have been recoded to produce different amino acids in this organism.1 TAA now encodes the amino acid lysine, while TAG encodes glutamic acid, according to research from Earlham Institute and University of Oxford.1 Dr. Jamie McGowan of the research team explained the unusualness of this finding, stating: "In almost every other case we know of, TAA and TAG change in tandem. When they aren't stop codons, they each specify the same amino acid."1
Subsequent investigations revealed that this genetic flexibility is more widespread in microorganisms than previously thought.1 Scientists discovered independent instances in at least five other ciliate species where the codon UAG had been reassigned to code for either leucine or glutamine rather than functioning as a stop signal.1 These findings suggest that the genetic code, long considered a universal constant of life, exhibits greater variability than conventional understanding would suggest.1
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