I received a livestream notification about the "Yunnan Butterfly Explosion" the moment I got to work. I'd been intrigued ever since seeing it on trending topics earlier β back in college, I followed two professors into the mountains to observe butterflies. One was a species identification expert, the other an entomologist. Both were inspiring mentors I deeply respect.
The more I think about butterflies, the more fascinating they become. Caterpillar and butterfly β same genome, yet two radically different lives. The genes are not replaced; the same genetic information is simply "interpreted" differently during metamorphosis. It is as if the same transcript gets spliced under a different scheme, emerging with entirely new form and function. This brings to mind an ancient saying β
Through change, there is passage; through passage, there is endurance.
In the context of molecular biology, it fits surprisingly well.
The human genome contains only about twenty thousand genes, yet it builds a life system of staggering complexity and diversity. The secret lies largely in post-transcriptional processing. The primary mRNA transcribed from DNA must have its introns spliced out and its exons joined together to form mature mRNA. But splicing is not a single-outcome process β the same primary transcript can retain or skip an intron, include or exclude an exon, even reorder the sequence of exons. With all these combinations in play, a single gene can generate dozens or even hundreds of mRNA variants, which are then translated into proteins with different functions.
This is alternative splicing.
The same gene, in different tissues and at different developmental stages, produces different proteins through different splicing patterns. In the nervous system, for example, the same gene can produce ion channel proteins sensitive to different neurotransmitters through alternative splicing, determining the specificity of neuronal signaling.
Another equally elegant mechanism is alternative polyadenylation.
The 3' end of an mRNA typically carries a poly(A) tail, which protects it from degradation and assists translation. But an mRNA molecule may harbor multiple potential polyadenylation sites. When a site closer to the transcription start point is chosen, the 3' end is shorter and carries fewer regulatory sequences, making the mRNA more susceptible to degradation. When a distal site is chosen, certain regulatory elements are retained, affecting the mRNA's intracellular localization and translation efficiency. By selecting different sites, the cell precisely tunes the lifespan and translation timing of its mRNAs.
A limited number of genes, yet through these "variations" the diversity of expression is vastly expanded β finite genetic information, endlessly giving rise to life.
Yunnan is the host province for the next Conference of the Parties to the Convention on Biological Diversity. Due to its unique geographic location, Ruili in Yunnan experienced a COVID-19 resurgence, which pushed the original May conference back to October. It is a shame that the timing would have coincided perfectly with the butterfly explosion.
If I remember correctly, tomorrow is International Biodiversity Day.
Why is biodiversity so important? The answer depends on one's outlook on the capacity of ecosystems for natural recovery β on our sense of ethics, and on our reverence for complexity. In an era of material abundance, Homo sapiens has leveraged natural resources and scientific technology to extend lifespans and ensure the stability of our species. To what extent these achievements threaten the survival of other organisms is, I think, not easy to gauge.
The extinction of a rare species rarely has visible consequences for the current generation, but we still do our best to approach the issue from a sustainability perspective. Those who hold opposing values rarely worry about resource depletion, yet they too face the challenge of disease. Viruses, as simple life forms, have brought about a pandemic of unprecedented scale in a globalized world. Cancer, meanwhile, is like a set of 23 volumes β each about a thousand pages β in which merely 40 to 60 typographical errors turn the text into life's most formidable final battle.
Fortunately, some wise people β hopefully not those who fancy Homo sapiens the master of the Earth β recognize that every species plays a subtle ecological role in the system, and advocate for action and attention to biodiversity conservation.
I am deeply moved by this.
From alternative splicing at the gene level to the coexistence of diverse species, "variation" is life's fundamental strategy for coping with finite resources β one gene produces multiple proteins through different splicing patterns, and one ecosystem maintains resilience through different species combinations. Same logic, different scale.
May the post-pandemic world be healthy, peaceful, renewed, and transformed β like a butterfly emerging from its cocoon.