Scientists have succeeded in unravelling the complete genome sequence of the common primrose -- the plant whose reproductive biology fascinated Victorian naturalist Charles Darwin.
Researchers at the University of East Anglia in the UK identified, for the first time, the landscape of genes which operate within the primrose's two different flowering forms that are involved in the reproductive process.
This adds fresh insight to a puzzle that scientists have been grappling with for over 150 years, according to the study published in the journal Scientific Reports.
Primula vulgaris plants flower in one of two ways; they either have a long style and low anthers, or a short style and elevated anthers -- known as pins or thrums.
Darwin was intrigued as to why some species, such as the primrose, develop two different forms of flowers, and devoted a whole book to the subject.
He concluded from his studies that they provided a mechanism to promote outcrossing between individuals.
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More recently, a cluster of genes known as the S (Style length) locus have been shown to be the control centre for the development of the flowers.
This S locus is absent from half the individuals of this species, this cluster switches some genes on and others off, giving different patterns of gene expression in pin and thrum flowers.
The team, based at the Earlham Institute in the UK, has previously sequenced the S-locus and described aspects of its evolution.
The research describes the full sequence of the P vulgaris genome and shows that the S locus controls hundreds of genes across the genome.
The team also identified genes that are activated in its absence, in the pin form of the flower.
"We started many years ago with a packet of seeds and a vision to understand the molecular genetics and developmental biology of the reproductive system Darwin described in 1862," said Philip Gilmartin of the University of East Anglia and Earlham Institute.
"Completion of the genome sequence paves the way to identify the genes that are regulated by the S locus, and adds more pieces to the puzzle," Gilmartin said.
"A long line of scientists, from Darwin in the 1860s through Bateson in the early 1900s, to Haldane and Fisher in the mid 1900's have been gripped and we continue to unravel the mystery piece by piece," he said.