Archive for the ‘evolution’ tag
Across northwestern North America, every example of a common peat moss called Sphagnum subnitens is genetically identical, researchers have discovered.
That means every specimen can be traced back to a single parent, which likely conquered North America in less than 300 years, and shows how a single ‘general purpose’ genome can allow a plant to grow in a range of climates. more
Where Phlox drummondii lives by itself, it has a periwinkle blue blossom. But where its range overlaps with Phlox cuspidata, which is also light blue, drummondii flowers appear darker and more red. Some individual butterflies prefer light blue blossoms and will go from blue to blue, avoiding the dark reds. Other individual butterflies prefer the reds and will stick with those. This “constancy” prevents hybrid crosses.
Hybrid offspring between drummondii and cuspidata turn out to be nearly sterile, making the next generation a genetic dead-end. The persistent force of natural selection tends to push the plants toward avoiding those less fruitful crosses, and encourages breeding true to type. In this case, selection apparently worked upon floral color. source
From southern Africa’s pineapple lily to Western Australia’s swamp bottlebrush, flowering plants are everywhere. Also called angiosperms, they make up 90 percent of all land-based, plant life.
New research published this week in the Proceedings of the National Academy of Sciences provides new insights into their genetic origin, an evolutionary innovation that quickly gave rise to many diverse flowering plants more than 130 million years ago. Moreover, a flower with genetic programming similar to a water lily may have started it all.
“Water lilies and avocado flowers are essentially ‘genetic fossils’ still carrying genetic instructions that would have allowed the transformation of gymnosperm cones into flowers,” said biologist Doug Soltis, co-lead researcher at the University of Florida in Gainesville.
Gymnosperms are a group of seed-bearing plants that include conifers and cycads that produce “cones” as reproductive structures, one example being the well-known pine cone. “We show how the first flowering plants evolved from pre-existing genetic programs found in gymnosperm cones and then developed into the diversity of flowering plants we see today,” he said. “A genetic program in the gymnosperm cone was modified to make the first flower.”
But, herein is the riddle. How can flowers that contain both male and female parts develop from plants that produce cones when individual cones are either male or female? The solution, say researchers, is that a male gymnosperm cone has almost everything a flower has in terms of its genetic wiring.
Somehow a genetic change took place allowing a male cone to produce female organs as well–and, perhaps more importantly, allowed it to produce showy petal-like organs that enticed new interactions with pollination agents such as bees.
Analyzing genetic information encoded in a diverse array of evolutionarily distant flowers–water lily, avocado, California poppy and a small flowering plant frequently used by scientists as a model, Arabidopsis–researchers discovered support for the single cone theory.
A non-flowering seed plant, a cycad named Zamia, which makes pine cone-like structures instead of flowers, was also examined in the study.
“We extracted an essential genetic material, RNA, from the flowers’ specific floral organs and in the case of Zamia, its cones, to see which genes were active,” said co-lead investigator Pam Soltis, a curator at the Florida Museum of Natural History and an evolutionary geneticist at the University of Florida.
Researchers then compared the organs’ profiles to a range of species representing ancient and more recent lineages of flowering plants. “This comparison allowed us to see aspects of the floral genetic program that are shared with gymnosperms, where they came from and also which aspects are shared among different groups of flowering plants and which differ,” she explained.
The flowers of most angiosperms have four distinct organs: sepals, typically green; petals, typically colorful; stamens, male organs that produce pollen; and carpels, female organs that produce eggs. However, the flowers of more ancient lineages of angiosperms have organs that intergrade, or merge into one another through a gradual series of evolutionary reforms. For example, a stamen of a water lily produces pollen but it may also be petal-like and colorful and there is often no distinction between sepals and petals–instead, early flowers have organs called tepals.
The research team found a very significant degree of genetic overlap among intergrading floral organs in water lilies and avocado but less overlap in poppy and Arabidopsis. “In other words, the boundaries between the floral organs are not all that sharp in the early angiosperm groups-the organs are still being sorted out in a sense,” said Doug Soltis.
The finding challenged researcher expectations that each floral organ in early angiosperms would have a unique set of genetic instructions as is the case in the evolutionarily derived Arabidopsis. Instead, the finding increased the likelihood that a single male cone was responsible for the world’s first flowering plants owing to the elasticity of their genetic structure.
“In early flowers, a stamen is not much different genetically speaking than a tepal,” said Doug Soltis. “The clearly distinct floral organs we all know and love today came later in flowering plant evolution–not immediately.”
Researchers say better understanding of these genetic switches in early angiosperm flowers could one day help scientists in other disciplines such as medicine or agriculture.
This project was conducted in collaboration with scientists at Penn State University, University at Buffalo, University of Georgia, and Fudan University in Shanghai, China. It was funded in part by the National Science Foundation’s Directorate of Biological Sciences.
Research by University of Leeds plant scientists has uncovered a snapshot of evolution in progress, by tracing how a gene mutation over 100 million years ago led flowers to make male and female parts in different ways.
The findings — published in the Proceedings of the National Academy of Sciences (PNAS) Online Early Edition — provide a perfect example of how diversity stems from such genetic ‘mistakes’. The research also opens the door to further investigation into how plants make flowers — the origins of the seeds and fruits that we eat.
In a number of plants, the gene involved in making male and female organs has duplicated to create two, very similar, copies. In rockcress (Arabidopsis), one copy still makes male and female parts, but the other copy has taken on a completely new role: it makes seed pods shatter open. In snapdragons (Antirrhinum), both genes are still linked to sex organs, but one copy makes mainly female parts, while still retaining a small role in male organs — but the other copy can only make male.
“Snapdragons are on the cusp of splitting the job of making male and female organs between these two genes, a key moment in the evolutionary process,” says lead researcher Professor of Plant Development, Brendan Davies, from Leeds’ Faculty of Biological Sciences. “More genes with different roles gives an organism added complexity and opens the door to diversification and the creation of new species.”
By tracing back through the evolutionary ‘tree’ for flowering plants, the researchers calculate the gene duplication took place around 120 million years ago. But the mutation which separates how snapdragons and rock cress use this extra gene happened around 20 million years later.
The researchers have discovered that the different behaviour of the gene in each plant is linked to one amino acid. Although the genes look very similar, the proteins they encode don’t always have this amino acid. When it is present, the activity of the protein is limited to making only male parts. When the amino acid isn’t there, the protein is able to interact with a range of other proteins involved in flower production, enabling it to make both male and female parts.
“A small mutation in the gene fools the plant’s machinery to insert an extra amino acid and this tiny change has created a dramatic difference in how these plants control making their reproductive organs,” says Professor Davies. “This is evolution in action, although we don’t know yet whether this mutation will turn out to be a dead end and go no further or whether it might lead to further complexities.
“Our research is an excellent example of how a chance imperfection sparks evolutionary change. If we lived in a perfect world, it would be a much less interesting one, with no diversity and no chance for new species to develop.”
The researchers now plan to study the protein interactions which enable the production of both male and female parts as part of further investigation into the genetic basis by which plants produce flowers. source 1, source 2, source 3