Scientists at the CSIR-Centre for Cellular and Molecular Biology (CCMB) in Hyderabad have uncovered a key genetic innovation that could solve Charles Darwin’s so-called “abominable mystery”: the rapid and diverse emergence of flowering plants roughly 130 million years ago.
The study, published recently in Nature Plants, reveals that a newly identified gene, named SHUKR, meaning “sperm” in several Indian languages, plays a crucial role in how flowering plants develop pollen and adapt to varied environments.
The research offers rare molecular insight into the sudden evolutionary success of flowering plants, which now dominate most terrestrial ecosystems and form the basis of the global food supply.
Darwin was perplexed by the fossil record suggesting a rapid diversification of flowering plants, or angiosperms, in the Early Cretaceous period. This sudden appearance stood in stark contrast to the slow and gradual change he observed elsewhere in nature, prompting him to call it an “abominable mystery.”
Scientists have long known that plant life cycles involve alternating generations: the gametophyte (which produces sperm or egg) and the sporophyte (which produces spores).
Early land plants like mosses spend most of their lives in the gametophyte phase, with water-dependent fertilization. But flowering plants reversed this emphasis, spending the majority of their lives in the sporophyte phase and evolving efficient methods for reproduction through enclosed pollen and seeds.
Until now, it was believed that flowering plant gametophytes developed independently of the sporophyte phase. But the CCMB team’s findings challenge that assumption.
The SHUKR Discovery
Led by eminent plant geneticist Dr. Imran Siddiqi, the CCMB team focused their research on Arabidopsis thaliana, a widely used model organism in plant biology.
They identified the SHUKR gene, which is expressed in sporophyte cells and directly influences the development of viable pollen, a key function of the male gametophyte.
The gene was also shown to regulate F-box genes, which are responsible for protein turnover during pollen formation. These proteins ensure the correct timing and composition of molecular signals needed to generate viable pollen.
What’s more, SHUKR and its downstream F-box genes are rapidly evolving. This adaptability, the researchers suggest, may have enabled flowering plants, especially the eudicots, which comprise about 75% of all angiosperms, to quickly colonize diverse ecological niches with varying environmental conditions such as temperature, humidity, and aridity.
SHUKR’s emergence roughly 125 million years ago coincides with the burst of angiosperm diversity that baffled Darwin.
According to the CCMB researchers, this gene may have allowed early flowering plants to fine-tune their reproductive mechanisms based on environmental cues, giving them an edge in survival and reproduction.
This genetic innovation may explain how flowering plants rapidly overtook other plant lineages to dominate Earth’s landscapes, and eventually support the rise of complex terrestrial ecosystems-including human agriculture.
The discovery could have wide-ranging applications in agriculture and food security, especially as the planet warms.
Rising temperatures have already been linked to male sterility in many crops due to heat-induced pollen failure. Understanding genes like SHUKR could help scientists develop new varieties of plants that remain fertile under climate stress, ensuring consistent yields.
The discovery also paves the way for precision breeding, where plants can be selected or modified for specific environmental fitness using their own biological mechanisms, rather than relying solely on external inputs or genetic modification.
