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Plant Science

Plants can be larks or night owls just like us

By | News, Plant Science

Plants have the same variation in body clocks as that found in humans, according to new research that explores the genes governing circadian rhythms in plants.

The research shows a single letter change in their DNA code can potentially decide whether a plant is a lark or a night owl. The findings may help farmers and crop breeders to select plants with clocks that are best suited to their location, helping to boost yield and even the ability to withstand climate change.

The circadian clock is the molecular metronome which guides organisms through day and night – cockadoodledooing the arrival of morning and drawing the curtains closed at night. In plants, it regulates a wide range of processes, from priming photosynthesis at dawn through to regulating flowering time.

These rhythmic patterns can vary depending on geography, latitude, climate and seasons – with plant clocks having to adapt to cope best with the local conditions. 

Researchers at the Earlham Institute and John Innes Centre in Norwich wanted to better understand how much circadian variation exists naturally, with the ultimate goal of breeding crops that are more resilient to local changes in the environment – a pressing threat with climate change.

To investigate the genetic basis of these local differences, the team examined varying circadian rhythms in Swedish Arabidopsis plants to identify and validate genes linked to the changing tick of the clock.

Dr Hannah Rees, a postdoctoral researcher at the Earlham Institute and author of the paper, said: “A plant’s overall health is heavily influenced by how closely its circadian clock is synchronised to the length of each day and the passing of seasons. An accurate body clock can give it an edge over competitors, predators and pathogens.

“We were interested to see how plant circadian clocks would be affected in Sweden; a country that experiences extreme variations in daylight hours and climate. Understanding the genetics behind body clock variation and adaptation could help us breed more climate-resilient crops in other regions.”

The team studied the genes in 191 different varieties of Arabidopsis obtained from across the whole of Sweden. They were looking for tiny differences in genes between these plants which might explain the differences in circadian function.

Their analysis revealed that a single DNA base-pair change in a specific gene – COR28 – was more likely to be found in plants that flowered late and had a longer period length. COR28 is a known coordinator of flowering time, freezing tolerance and the circadian clock; all of which may influence local adaptation in Sweden.

“It’s amazing that just one base-pair change within the sequence of a single gene can influence how quickly the clock ticks,” explained Dr Rees.

The scientists also used a pioneering delayed fluorescence imaging method to screen plants with differently-tuned circadian clocks. They showed there was over 10 hours difference between the clocks of the earliest risers and latest phased plants – akin to the plants working opposite shift patterns. Both geography and the genetic ancestry of the plant appeared to have an influence. 

“Arabidopsis thaliana is a model plant system,” said Dr Rees. “It was the first plant to have its genome sequenced and it’s been extensively studied in circadian biology, but this is the first time anyone has performed this type of association study to find the genes responsible for different clock types.

“Our findings highlight some interesting genes that might present targets for crop breeders, and provide a platform for future research. Our delayed fluorescence imaging system can be used on any green photosynthetic material, making it applicable to a wide range of plants. The next step will be to apply these findings to key agricultural crops, including brassicas and wheat.” 

Read the paper: Plant, Cell & Environment

Article source: Earlham Institute

Image credit: Earlham Institute

Ancient DNA Continues To Rewrite Corn’s 9,000-Year Society-Shaping History

By | Agriculture, News, Plant Science

Some 9,000 years ago, corn as it is known today did not exist. Ancient peoples in southwestern Mexico encountered a wild grass called teosinte that offered ears smaller than a pinky finger with just a handful of stony kernels. But by stroke of genius or necessity, these Indigenous cultivators saw potential in the grain, adding it to their diets and putting it on a path to become a domesticated crop that now feeds billions.

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What makes peppers blush

By | Agriculture, Fruits and Vegetables, News, Plant Science

Bright red, tasty and healthy, that’s how we know and love bell peppers. A research team has deciphered in detail at the protein level what makes them turn red as they ripen. At the heart of the project are the so-called plastids, typical plant cell organelles in which chlorophyll is broken down and carotenoids are produced as the fruit ripens. Visually, this transformation is clearly visible in the colour change from green to orange or red.

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Chloroplasts on the move

By | News, Plant Science

How different plants can share their genetic material with each other

The genetic material of plants, animals and humans is well protected in the nucleus of each cell and stores all the information that forms an organism. For example, information about the size or color of flowers, hair or fur is predefined here. In addition, cells contain small organelles that contain their own genetic material. These include chloroplasts in plants, which play a key role in photosynthesis, and mitochondria, which are found in all living organisms and represent the power plants of every cell. But is the genetic material actually permanently stored within one cell? No! As so far known, the genetic material can migrate from cell to cell and thus even be exchanged between different organisms. Researchers at the Max Planck Institute of Molecular Plant Physiology (MPI-MP) in Potsdam have now been able to use new experimental approaches to show for the first time how the genetic material travels. They published their results in the journal Science Advances.

The transfer of genetic material occurs quite frequently in plants. This can either result in a new combination of the genetic material, or alternatively the recipient cell can establish both genetic variants in parallel. This union of two different genomes, called allopolyploidization, is very interesting in evolutionary terms, as it leads to the formation of new plant species and is widespread in many plant groups. Many important crops, such as bread and durum wheat, oats, cotton, canola, coffee, and tobacco have such combined genomes from at least two crossed species.

In order to understand the mechanisms of genome transfer from cell to cell, the researchers led by Ralph Bock at MPI-MP conducted experiments with tobacco plants using grafting, which is commonly used in agriculture. Here, two different tobacco plants were grafted onto each other and the cells of the junction were observed microscopically in real time. To differentiate between the genome of nucleus and plastids, fluorescent reporter proteins were integrated and expressed from both genomes and the researchers used a trick using a specialization of the chloroplasts. In the plastids, a gene is integrated by transformation that encodes a chloroplast-specific fluorescence protein, which is produced exclusively in plastids and cannot leave them. This creates an absolutely specific and stable label for the plastids.

After a short time, the two partners grow together at the graft junction, resulting in a physiological connection between the two plants. “We were able to observe that genome transfer from cell to cell occurs in both directions with high frequency at this site”, explains Dr. Alexander Hertle, first author of the study.

Using a new experimental setup, the researchers were able to observe structural changes in the cell walls in the wound tissue of the graft site. “The cell walls formed protrusions, creating junctions between the two partners. The size of those created pores allows the migration of an entire plastid. Therefore, the genome does not migrate freely, but encapsulated from cell to cell,” Hertle continues. However, to actually make this possible, the plastids have to shrink and become mobile. These rod-shaped plastids are equal to an amoeba and grow back to normal size after transfer into the target tissue.

The researchers have thus uncovered a new pathway for intercellular exchange of very large cell structures, which may also be used by parasitic plants, such as mistletoe, to carry out gene exchange with their host. In addition, it now needs to be clarified whether mitochondria and the nuclear genome also use similar transfer mechanisms.

Read the paper: Science Advances

Article source: Max Planck Institute of Molecular Plant Physiology

Image credit: A natural stem graft between a beech (front) and a maple (back) in a forest near Monroe, New Jersey (left picture), and an similar stem graft between two tobacco plants (right) in the greenhouse. MPI-MP