51-million-year old mystery solved as researchers find what led to Darwin’s theory of supergene

Researchers decode 51-million-year old secret to Darwin's theory of supergene

In a breakthrough, researchers have decoded the 51.7 million-year-old genetic secret to a theory given by the father of evolution Charles Darwin nearly 150 years ago.

Since the start of 16th century, biologists knew that different forms of flowers are due to different positions of the male and female sex organs and Darwin named this phenomenon as “heterostyly” nearly 150 years ago. The phenomenon prevents pollinating insects from fertilising flowers of the same type which is crucial because it promotes cross-pollination between different types of plants and produces different types of offspring through natural selection.

Darwin stated that some plant species have evolved to have two distinct forms of flower where male and female reproductive organs are of different lengths, and have evolved to promote cross-pollination by insects.

His two forms of flowers are now known as ‘pins’ (female stigma and style are greatly elongated, male anthers are shortened) and ‘thrums’ (the pins reverse — female parts shortened and male organs extended) which are foundation of modern genetic theory. These clusters of genes are called supergenes because they act together as a unit and control complex biological mechanisms. The heterostyly supergene is called S locus. 

After centuries, researchers have now decoded which part of the genetic code made them that way. Researchers from the University of East Anglia (UEA) in the UK have conducted the study and found that the genetic code that results in such variation is due to a process that occurred more than 51 million years ago.

“To identify the genes which control the biology noted by Darwin is an exciting moment. Many studies have been done over the past decades to explore the genetic basis of this phenomenon but now we have pinpointed the supergene directly responsible, the S locus,” said Professor Philip Gilmartin from UEA’s School of Biological Sciences.

Researchers sequenced the Primula genome and found that the supergene is a duplicate of six-year-old gene that controls the identity of petals on a Primula flower. Study authors revealed that the gene duplicates itself, inserts itself in the S locus and mutates to control the position of the anther in the flower. Researchers solved the mystery of mutation by finding the duplicate gene which was not known yet.

“Understanding of the genetics which underpin flower development and reproduction of a species broadens our knowledge about the entire system of pollination, which underpins biodiversity and food security,” noted Gilmartin about the study’s importance.

“With challenges such as climate change and its effects on plants, crops and their insect pollinators, it’s even more important to understand pollination mechanisms and how species can and will react.”

The study appeared in the journal Nature Plants.

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