Iron (Fe) is an essential micronutrient for plant growth and development, and participates in many biological processes. Fe deficiency was shown to delay flowering time which influences the quantity and quality of the progenies of angiosperms. However, the connection between Fe deficiency and flowering is obscure.
In a study published in Plant Science, the researchers from Xishuangbanna Tropical Botanical Garden (XTBG) of the Chinese Academy of Sciences and Yunnan University explored the nexus between flowering and Fe deficiency by investigating the function of the Fe-deficiency-induced transcription factors bHLH38, bHLH100, and bHLH101 (bHLH38/100/101) in the control of flowering time.
The researchers first investigated whether the flowering time of wild-type plants was affected by Fe-deficiency treatment, and found that Fe deficiency had a negative influence on flowering time under long days.
Through phenotype analysis, they then analyzed the expression levels of the flowering-related genes CONSTANS (CO), FLOWERING LOCUS T (FT) and others in the bhlh38/100/101 triple mutant, and verified the relationship between bHLH38/100/101 and FT.
The transcription of bHLH38/100/101 increased in the morning under normal growth conditions. The proteins functioned antagonistically with CO or other flowering activators to inhibit flowering. Under Fe deficiency, expression of bHLH38/100/101 was strongly induced and, subsequently, excessed bHLH38/100/101 interaction with CO and restricted the function of CO to promote flowering.
“Our results indicated that iron deficiency affects flowering of Arabidopsis under long days through bHLH38/100/101–CO–FT signaling,” said LIANG Gang from XTBG.
Mosses and flowering plants took different genetic routes to evolve a similar defense mechanism
A team led by plant biologists at the Universities of Freiburg and Göttingen in Germany has shown for the first time that mosses have a mechanism to protect them against cold that was previously known only in flowering plants. Professor Ralf Reski at the Cluster of Excellence Centre for Integrative Biological Signalling Studies (CIBSS) at the University of Freiburg and Professor Ivo Feussner at the Center for Molecular Biosciences (GZMB) at the University of Göttingen have also demonstrated that this mechanism has an evolutionarily independent origin – mosses and flowering plants use a similar mechanism that hinges on distantly related genes. Moreover, it protects the organisms against pathogens as well as cold. The moss Physcomitrella and the flowering plant Arabidopsis served as model organisms. The team has published its study in the journal Nature Plants.
More than 500 million years ago plants began to leave the water and colonize the land. Mosses and flowering plants diverged evolutionarily from a common ancestral plant. However, both had to find ways to protect themselves from low temperatures on land. For example, it is vital for all plants to maintain the fluidity of their cell membranes. Only sufficiently fluid membranes enable transport processes across the barrier that surrounds a plant cell as a protective envelope. When the temperature drops, the membrane hardens and becomes less permeable, which impairs cell functions. Plants can counteract this as their cell membranes contain lipids, which contain fatty acids. The more unsaturated fatty acids these lipids contain, the lower the temperature at which the membrane solidifies.
The research team from Freiburg and Göttingen has identified a new protein that plays an essential role in the regulation of fluidity in mosses. It influences the degree of saturation of fatty acids in a group of membrane lipids known as sphingolipids. When the researchers deleted the gene responsible for the formation of this protein, they found that the plants were more sensitive to cold. At the same time, they were more susceptible to oomycetes – filamentous organisms related to algae that include pathogens of plant diseases such as downy mildew and potato blight.
“Sphingolipids are important building blocks of cell recognition and signal transduction in humans, animals and plants. We have discovered a previously unknown regulator of these sphingolipids in moss and shown that it also functions in a flowering plant. This opens up completely new possibilities in synthetic biology,” Reski explains.
Feussner adds “Our work shows that mosses and flowering plants have followed different pathways during evolution to adjust membrane fluidity in cold conditions in a similar way. This is an impressive example of convergence in plant evolution at the molecular level.”
How mosses acquired this particular gene is unclear. The team found it also in the genome data of fungi, choanoflagellates, diatoms and a small group of unicellular algae that have been little studied so far.
Featured image: Convergent evolutionary origin of sphingolipid modification. Graphics: Jan de Vries
Reference: Hanno Christoph Resemann, Cornelia Herrfurth, Kirstin Feussner, Ellen Hornung, Anna K. Ostendorf, Jasmin Gömann, Jennifer Mittag, Nico van Gessel, Jan de Vries, Jutta Ludwig-Müller, Jennifer Markham, Ralf Reski, Ivo Feussner (2021): Convergence of sphingolipid desaturation across over 500 million years of plant evolution. In: Nature Plants. DOI: 10.1038/s41477-020-00844-3
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.”
The results of the study have been published in the journal Plant, Cell and Environment.
NASA astronaut Kate Rubins poses next to a thriving radish crop growing inside the Advanced Plant Habitat in the International Space Station.
Located in Europe’s Columbus module, the NASA experiment is the latest in the study of plants growing in microgravity.
With plans to visit the Moon and Mars, future astronauts will need a regular, fresh source of food as they take on these missions farther away from home. In addition to providing much-needed vitamins and minerals, growing plants in space contributes to sustainability and adds homey touch to exploration.
Because plants no longer have gravity to root them to soil, the seeds are grown in ‘pillows’ that help evenly distribute fertilizer and water to the roots.
Radishes were chosen because it is a model plant; they have a short cultivation period and are genetically similar to the plant most frequently studied in space, Arabidopsis. Radishes are also edible and nutritious, with this batch ready for harvest any day now. Samples will be sent back to Earth for study.
The Advanced Plant Habitat is a self-contained growth chamber requiring very little intervention from astronauts. It is equipped with LED lights, porous clay, over 180 sensors and cameras regulated by researchers at NASA’s Kennedy Space Center in Florida, USA. From there, plant growth is monitored and conditions adjusted as necessary to better distribute water and fertilizer and control moisture and temperature levels.
The next ESA astronaut to launch to the Station is Thomas Pesquet for mission Alpha. Slated to arrive in Spring 2021, perhaps Thomas will get to try another batch of space-grown greens.
Plants have the unique capability to sense and adapt to changes in their environment
This information is stored in the form of ‘epigenetic memory’ which can be passed on to the offspring, resulting in defects in growth and development.
Researchers have identified two proteins responsible for erasing plant memory to maximise chances of offspring survival.
Researchers at the University of Warwick have uncovered the mechanism that allows plants to pass on their ‘memories’ to offspring, which results in growth and developmental defects.
In order to survive and thrive, plants have the unique capability to sense and remember changes in their environment. This is linked to the chemical modification of DNA and histone proteins, which alters the way in which DNA is packaged within the cell’s nucleus and genes are expressed – a process known as epigenetic regulation.
Usually, this epigenetic information is reset during sexual reproduction to erase any inappropriate ‘memories’ from being passed on to ensure the offspring grows normally. In the paper, ‘A new role for histone demethylases in the maintenance of plant genome integrity’ published in the journal elife, it was found that some plants were unable to forget this information and passed it on to their offspring, thereby affecting their chances of survival.
The researchers identified two proteins in Thale Cress (Arabidopsis), previously known only to control the initiation and timing of flowering, that are also responsible for controlling ‘plant memory’ through the chemical modification (demethylation) of histone proteins.
They showed that plants unable to reset these chemical marks during sexual reproduction, passed on this ‘memory’ to subsequent generations, resulting in defects in growth and development.
Some of these defects were linked to the activation of selfish DNA elements, also known as ‘jumping genes’ or transposons, thus indicating that the erasure of such ‘memory’ is also critical for maintaining the integrity of plant genomes by silencing transposons.
Prof. Jose Gutierrez-Marcos, a senior author on the paper from the School of Life Sciences at the University of Warwick commented:
“Our study into the proteins that regulate plant memory has shown how important it is for chemical marks to be reset during sexual reproduction in order to avoid offspring inheriting inappropriate ‘memories’ that lead to growth and developmental defects associated with genome instability.
“The next step is to work out how to manipulate such ‘memories’ for plant breeding purposes, so that subsequent generations show greater adaptability to allow them to thrive in a changing environment.”
This work was carried out by an international team of researchers based at the University of Warwick (UK), Université Paris Saclay (France), Max Planck Institute for Developmental Biology (Germany), The Ohio State University and Donald Danforth Plant Science Center (USA) and Nagoya University (Japan).