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If you know the enemy and know yourself, you need not fear the result of a hundred battles.
– Sun Tzu, The Art of War

Who Are You?

How do plants distinguish “unfriendly” (a.k.a., pathogenic) microbes from “friendly” microbes (with which to form mutually beneficial partnerships, e.g.)?

How do flowering plants choose their mating partners in order to promote outcrossing?

There is evidence that some plants can distinguish the roots of related (“kin”) from non-related neighboring plants. How does this “kin recognition” work in plants?

All of the above situations involve the concept of biological “self” versus “non-self” perception.

It turns out that how plants distinguish “self” from “non-self” is critically important for plant defense, mutualistic symbioses, successful sexual reproduction in many flowering plants, and maybe even root-root interactions among different plant species.

Pattern Recognition in Plant Defense and Symbiosis

One of the most important defense mechanisms against microbial pathogens is a plant’s innate immune system. But what triggers the plant’s immune system to switch the plant from growth and development into a defense mode?

The ability to distinguish ‘self’ from ‘nonself’ is the most fundamental aspect of any immune system. The evolutionary solution in plants to the problems of perceiving and responding to pathogens involves surveillance of nonself, damaged-self and altered-self as danger signals.” (From Ref. 1 below)

As mentioned in the previous post, these “danger signals” are distinct, small fragments of cells, either from the plant itself (“self”) or from another biological entity (“non-self”). Plant cells may have an array of different cell-surface receptors, each one activated by a specific cellular fragment.

In other words, “The first line of defense in plants is the recognition of conserved molecules characteristic of many microbes. These elicitors are also known as microbe- or pathogen-associated molecular patterns (MAMPs or PAMPs). MAMPs are essential structures for the microbes and are for that reason conserved both among pathogens, non-pathogenic and saprophytic microorganisms. MAMPs are recognized by pattern recognition receptors (PRRs), which are localized on the surface of plant cells…” (From Ref. 2 below.)

Recognition of pathogen-derived molecules by pattern recognition receptors (PRRs) is a common feature of both animal and plant innate immune systems. In plants, PRR signaling is initiated at the cell surface by kinase complexes, resulting in the activation of immune responses that repel microbes.

“PRRs were first discovered in plants. Since that time many plant PRRs have been predicted by genomic analysis (370 in rice; 47 in Arabidopsis). Unlike animal PRRs, which associated with intracellular kinases via adaptor proteins, plant PRRs are composed of an extracellular domain, transmembrane domain, juxtamembrane domain and intracellular kinase domain as part of a single protein.” (From Wikipedia)

Interestingly, some of these PRRs also mediate symbiotic signaling (see Ref. 3 below). That is, small, unique molecules from “friendly” microbes, such as Rhizobium bacteria or mycorrhizal fungi, may specifically interact with some plant PRRs, which, in turn, may set in motion “symbiotic” or “mutualistic” responses in the plant.

Recent findings suggest that, in some instances, the immune response may contribute to the process of symbiotic partner choice in plants (see Ref. 4).

In short, emerging data suggest that ‘know thyself’, or at least ‘know thy partner’, may be as essential for development of beneficial infections as it is in defence against disease.” (From Ref. 4 below)

To Be Continued….Self-incompatibilty and Kin Recognition

References

1. Sanabria, N. M., J.-C. Huang and I. A. Dubery (2010) “Self/non-self perception in plants in innate immunity and defense.” Self/Nonself, Vol. 1, pp. 40-54. (Full Text)

2. Newman, M.-A., T. Sundelin, J. T. Nielsen, and G. Erbs (2013) “MAMP (microbe-associated molecular pattern) triggered immunity in plants.” Frontiers in Plant Science, 4:139. doi: 10.3389/fpls.2013.00139 (Full Text)

3. Antolín-Llovera, M., et al. (2014) “Knowing your friends and foes – plant receptor-like kinases as initiators of symbiosis or defence.” New Phytologist, Vol. 204, pp. 791–802. (Full Text)

4. Saffo, M. B. (2014) “Mutualistic Symbioses.” In: eLS. John Wiley & Sons, Ltd: Chichester. DOI: 10.1002/9780470015902.a0003281.pub2 (Download PDF for Full Text)

The Who – Who Are You?

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The Selfish Plant

Looking Out For Number One

In a previous post, way back last December, regarding the notion of plant “pain”, I acknowledged the subject of “damaged-self recognition” in plants, but I didn’t want to elaborate on it at that time.

Well, it looks like now’s the time….

“Damaged-self recognition” in plants has to do with how a plant senses that it has been physically injured.

For example, how does a plant become aware that it’s been physically damaged – by a hailstorm, for instance, or by a herbivore? And can it tell the difference between the two?

It’s well-known that plants can, and do, respond at the whole-plant (systemic) level when a part of the plant has been physically damaged.

And recent experimental evidence tends to support the idea that plants can indeed distinguish different kinds of wounding – for example, caterpillar-chewing versus cattle-grazing – and respond differently to each.

If so, then what are the cellular and whole-plant mechanisms that enable plants to distinguish and to defend themselves against different kinds of wounding?

Perhaps the chief proponent (evangelist?) of the concept of “damaged-self recognition” in plants is Dr. Martin Heil. (See also an interview with Martin Heil.)

In his words, here is a partial definition:
Most elicitors of plant responses to folivory represent, or contain, parts of plant-derived molecules that are degraded, digested or localized outside their original cell compartment. To the plant, these
elicitors indicate the ‘damaged self’. Such elicitors are released from disrupted cells and are probably perceived by receptors that monitor the extracellular chemistry. Thus, the information on the ‘damaged self’ is transported into the inner compartments of intact and metabolically active cells, which react through metabolic responses such as the synthesis of systemic signals and defence compounds.
” (From: Ref. 1 below)

Briefly put, when a leaf, for example, is grazed by a herbivore (“folivore”), this produces broken pieces of plant cells and plant cell walls. These cellular fragments (“elicitors”) diffuse to surrounding intact cells, which may contain specific receptors for some of these elicitors.

When these elicitor-receptors are activated, they trigger a chain of cellular processes that lead to the production of chemical “wound signals” that can diffuse throughout the plant, alerting it to the damage and initiating various defensive responses.

PAMPs, MAMPs, DAMPs and HAMPs

Multicellular organisms suffer injury and serve as hosts for microorganisms. Therefore, they require mechanisms to detect injury and to distinguish the self from the non-self and the harmless non-self (microbial mutualists and commensals) from the detrimental non-self (pathogens).” (From Ref. 3 below)

The concept that animals and plants achieve the above by detecting specific molecules produced by, or on the surface of, microbes has been around a long time.

Immunologists were likely among the first to identify and characterize such molecules. They discovered that cells of the immune system were activated by specific molecules associated with groups of pathogens. They called these elicitors of the immune response pathogen-associated molecular patterns (PAMPs).

Since then, this concept has expanded and diversified well beyond the field of immunology, even into the realm of plant science.

So, for example, today we now have MAMPs (microbe-associated molecular patterns) that are recognized by the plant innate immune systems pattern recognition receptors (PRRs).

In more general terms, we also have damage-associated molecular patterns (DAMPs), also known as “danger-associated molecular patterns” or simply “danger signals”. For example, these may be molecular pieces of plant cells themselves that can act as “elicitors”, as mentioned above. (Please see Ref. 3 below.)

And, finally, we have “herbivore-associated molecular patterns” (HAMPs) that include specific molecules derived from the regurgitate of feeding caterpillars and also plant-derived protein fragments that are formed specifically during insect feeding. Interestingly, a plant’s defensive responses elicited by HAMPs may differ from those triggered by DAMPs.

Recent research (see Ref. 4 below) indicates that plants may also use a combination of DAMPs and HAMPs as cues in order to deploy a more fine-tuned response to specific wounding.

Thus, a plant may possess quite sophisticated mechanisms – as yet to be fully understood – that allows it to not only perceive “damaged-self” but also damage by “non-self”.

The Selfish Plant

Delving into the subject of “damaged-self recognition” in plants got me to thinking about other ways plants display an awareness of self. (Dare I say “selfishness”?)

No, I’m not going to investigate the subject of self-aware plants as it relates to plant “consciousness”. (For that, I’ll refer you to Ref. 5 below.)

Instead, over the next few posts, lets’s explore the nature of what I’ll call “the selfish plant”.

Next-Up: Self- and Non-Self Recognition in Plants

References

1. Heil, M. (2009) “Damaged-self recognition in plant herbivore defence.” Trends in Plant Science, Vol. 14, pp. 356-363. (Abstract)

2. Heil, M., et al. (2012) “How Plants Sense Wounds: Damaged-Self Recognition Is Based on Plant-Derived Elicitors and Induces Octadecanoid Signaling.” PLoS ONE 7(2): e30537. doi:10.1371/journal.pone.0030537. (Full Text)

3. Heil, M. and W. G. Land (2014) “Danger signals – damaged-self recognition across the tree of life.” Frontiers in Plant Science, Vol. 5, article 578. DOI: 10.3389/fpls.2014.00578. (Full Text)

4. Duran-Flores, D. and M. Heil (2016) “Sources of specificity in plant damaged-self recognition.” Current Opinion in Plant Biology, Vol. 32, pp. 77-87. (Abstract)

5. Trewavas, A. J. and F. Baluška (2011) “The ubiquity of consciousness.” EMBO Reports, Vol. 12, pp. 1221-1225. (Full Text)

HowPlantsWork © 2008-2017 All Rights Reserved.

From A Pumpkin Movie to Jimi Hendrix

Yep, the plant news from last month was quite diverse.

Let’s start with two movies – one happens over a time scale of months, and the other happens over a time scale of billionths of seconds.

  • Over the course of five months in 2014 — from a sprouting seed to a fair-ready 1,223 pound pumpkin — competitive pumpkin grower Matt Radach protected and pampered his growing plant, as captured in this time lapse video.

    Growing a 1,223 pound pumpkin from seed to scale in time lapse.

  • Using ultrafast imaging of moving energy in photosynthesis, scientists have determined the speed of crucial processes for the first time.

    First movie of energy transfer in photosynthesis solves decades-old debate.

  • As a growing plant extends its roots into the soil, the new cells that form at their tips assume different roles, from transporting water and nutrients to sensing gravity.
    A new study points to one way by which these newly-formed cells, which all contain the same DNA, take on their special identities.

    Transforming plant cells from generalists to specialists.

  • Sneaky parasitic weeds may steal genes from the plants they are attacking and use those genes against the host plant, according to a team of scientists.

    Parasitic weeds may steal genes from the plants they are attacking.

  • A team of researchers has named a new, rare and endangered succulent found only in Baja California after the rock legend.”

    Jimi Hendrix lends new plant species his name.

    Thanks for all the questions and comments in 2016, and for 2017, Happy Trails!

    HowPlantsWork © 2008-2017 All Rights Reserved.

  • From Where Potatoes Came From to Where Agriculture Is Going

    Last November the plant research news ranged from the past history of one of our most important crop plants to the future of agriculture in the 21st century.

  • November is the month of Thanksgiving in the USA, and one common feature of today’s Thanksgiving feasts was not present at the Pilgrim’s original one – potatoes.

    That’s because potatoes are native to South America and had not yet made their way to North America.
    Where in South America potatoes first became domesticated, however, is still unknown. Recent genetic studies point to the Andean highlands in southern Peru and northwestern Bolivia as the crop’s birthplace, but a lack of direct plant evidence has made it difficult to confirm.”

    Who First Farmed Potatoes? Archaeologists in Andes Find Evidence.

  • The fungus Piriformospora indica colonizes the roots of different plants. This can be orchids, tobacco, barley or even moss. It penetrates into the roots, but does not damage the plants.

    As reported in November of last year, a protein produced by this fungus may be able to suppress the innate immune system of its plant host.

    How a fungus inhibits the immune system of plants.

  • Farmers looking to reduce reliance on pesticides, herbicides and other pest management tools may want to heed the advice of Cornell agricultural scientists: Let nature be nature – to a degree.

    Wicked weeds may be agricultural angels.

  • Millions of years ago, some plants in the mustard family made the switch from simple leaves to complex leaves through two tiny tweaks to a single gene. One tweak to a small enhancer sequence gave the gene a new domain of expression in the leaf. Paradoxically, the other tweak sub-optimised its function in this new domain. But together, these changes gave rise to fit plants with complex leaves.

    A small piece of DNA with a large effect on leaf shape.

  • A decade ago, agricultural scientists at the University of Illinois suggested a bold approach to improve the food supply: tinker with photosynthesis, the chemical reaction powering nearly all life on Earth.
    The idea was greeted skeptically in scientific circles and ignored by funding agencies. But one outfit with deep pockets, the Bill and Melinda Gates Foundation, eventually paid attention, hoping the research might help alleviate global poverty.

    With an Eye on Hunger, Scientists See Promise in Genetic Tinkering of Plants.

    Next Up: The final chapter of the 2016 plant news retrospective.

    HowPlantsWork © 2008-2017 All Rights Reserved.

  • From Flowers That Smell Like Stressed Bees To Corn That Smells Like “Help Me!”

    October 2016 seemed to feature an unusual number of quirky plant news stories.

    For example, we previously saw an orchid that smelled like body odor, presumably to attract mosquitos.

    Now here’s another weird flower smell…

  • A new discovery takes plants’ deception of their pollinators to a whole new level. Researchers reporting in the journal Current Biology on October 6 found that the ornamental plant popularly known as Giant Ceropegia fools certain freeloading flies into pollinating it by mimicking the scent of honeybees under attack.

    This flower smells like a bee under attack.

  • Plants cannot simply relocate to better surroundings when their environmental conditions are no longer suitable. Instead, they have developed sophisticated molecular adaptation mechanisms. Scientists at the Technical University Munich (TUM) in cooperation with the Helmholtz Center Munich and the University of Nottingham have been able to demonstrate that brassinosteroids, which until now have mainly been regarded as growth hormones, increase the resistance of plants against frost.

    Defying frost and the cold with hormones.

  • Of the many elusive grails of agricultural biotechnology, the ability to confer nitrogen fixation into non-leguminous plants such as cereals ranks near the very top.

    Beyond genes: Protein atlas scores nitrogen fixing duet.

  • Here’s – by far – the most retweeted plant research news story of October 2016:

    It’s been a brutal forest fire season in California. But there’s actually a greater threat to California’s trees — the state’s record-setting drought. The lack of water has killed at least 60 million trees in the past four years.
    Scientists are struggling to understand which trees are most vulnerable to drought and how to keep the survivors alive. To that end, they’re sending human climbers and flying drones into the treetops, in a novel biological experiment.

    How Is A 1,600-Year-Old Tree Weathering California’s Drought?.

  • A photoreceptor molecule in plant cells has been found to moonlight as a thermometer after dark – allowing plants to read seasonal temperature changes. Scientists say the discovery could help breed crops that are more resilient to the temperatures expected to result from climate change.

    Plant ‘thermometer’ triggers springtime budding by measuring night-time heat.

  • When corn seedlings are nibbled by caterpillars, they defend themselves by releasing scent compounds that attract parasitic wasps whose larvae consume the caterpillar—but not all corn varieties are equally effective at giving the chemical signal for help.

    Researchers identify genes for “Help Me!” aromas from corn.

    Next Up: The penultimate look at plant news for 2016.

    HowPlantsWork © 2008-2017 All Rights Reserved.

  • From Plant Secrets To Plant Antibiotics

    What were the five most re-tweeted and favorited plant news stories that I shared in September of last year?

    Well, here they are, in order of popularity, lowest to highest.

  • Scientists from the John Innes Centre have pioneered innovative new cell imaging techniques to shed light on cells hidden deep inside the meristem. This new development has made it possible to explore further below the outer surface of plants and has uncovered how a key gene controls stem growth.

    Peeling back the layers: scientists use new techniques to uncover hidden secrets of plant stem development.

  • While we already knew that plant roots were capable of sensing many individual soil characteristics (water, nutrients and oxygen availability), we did not have any understanding of how they integrated these signals in order to respond in an appropriate way. Researchers from CNRS and INRA have just discovered a mechanism that allows a plant to adjust its water status and growth according to different soil flooding conditions.

    How plant roots sense and react to soil flooding.

  • “The mutualistic relationship between tree roots and ectomycorrhizal (ECM) fungi has been shaping forest ecosystems since their inception.

    How fungi help trees tolerate drought.

  • A team that includes a Virginia Tech plant scientist recently used life sciences technology to edit 14 target sites encompassing eight plant genes at a time, without making unintended changes elsewhere in the genome.
    The technology, a genome-editing tool called CRISPR-Cas9, revolutionized the life sciences when it appeared on the market in 2012. It is proving useful in the plant science community as a powerful tool for the improvement of agricultural crops.

    New study of CRISPR-Cas9 technology shows potential to improve crop efficiency.

  • One researcher thinks the drugs of the future might come from the past: botanical treatments long overlooked by Western medicine.

    Could ancient remedies hold the answer to the looming antibiotics crisis?

    So, ethnobotany actually wins over CRISPR-Cas9…

    Next-Up: What were some of the “tastier” plant science news stories in October 2016?

    HowPlantsWork © 2008-2017 All Rights Reserved.

  • From How Sunflowers Track The Sun To Where Strawberries Came From

    The eighth month of the year may be when many people are on holiday (at least in the Northern Hemisphere).

    But plant science news didn’t take a holiday.

    Indeed, there were so many popular reports published last August, it was difficult for me to select only a few.

    Anyway, here are five that you may find particularly “tasty”.

  • Sunflowers not only pivot to face the sun as it moves across the sky during the day, but they also rotate 180 degrees during the night to greet the morning sun. UC Davis and UC Berkeley researchers have now discovered how they do it:

    How sunflowers follow the sun.

  • How rapidly increasing levels of atmospheric CO2, due primarily to human activities, and its climatic consequences will affect the Earth’s terrestrial vegetation is currently one of the most important and active areas plant-related research. Two new findings reported in August 2016 contributed to our understanding of the changes that occurring.

    A University of Otago botany researcher and colleagues have developed a new system to map the world’s “biomes”— large-scale vegetation formations — that will provide an objective method for monitoring how vegetation reacts as climate changes.

    New map of world vegetation reveals substantial changes since 1980s.

    New research from the University of British Columbia suggests evolution is a driving mechanism behind plant migration, and that scientists may be underestimating how quickly species can move.

    Evolution drives how fast plants could migrate with climate change: UBC study.

  • Last August it was reported that a new way of fixing inactive proteins has been discovered in a single-celled algae.

    This repair system may have applications in agriculture and biotechnology because it could potentially be harnessed to enable proteins to become active only in the light.

    Novel “repair system” discovered in algae may yield new tools for biotechnology.

  • Scientists from the University of New Hampshire have unlocked a major genetic mystery of one of the ancestors of cultivated strawberry.

    UNH scientists unravel genetic ancestry of cultivated strawberry.

    Next-Time: Find out what the most re-tweeted plant research news stories were during September 2016.

    HowPlantsWork © 2008-2017 All Rights Reserved.

  • From A New Look At Lichens To A Moss Surprise

    July 2016 seemed to be a time to rethink several long-held presumptions about lichens and chloroplasts.

    A couple of plant research news reports changed the way we look at symbiotic plants and photosynthesis.

  • For over 140 years, lichens have been regarded as a symbiosis between a single fungus, usually an ascomycete, and a photosynthesizing partner. Other fungi have long been known to occur as occasional parasites or endophytes, but the one lichen–one fungus paradigm has seldom been questioned. Here we show that many common lichens are composed of the known ascomycete, the photosynthesizing partner, and, unexpectedly, specific basidiomycete yeasts.” (From: Science magazine)

    Two’s Company, Three’s a Lichen?

  • There exist more than 4,500 plant species which live as parasites on other plants. Some of them cause great damage to agriculture, even leading to the complete failure of crops. Researchers…have been investigating the ways in which some species defend themselves against such parasites.

    How the tomato avoids entanglements with a dodder.

  • Following the discovery of a new and very valuable enzyme which folds linear molecules into different shapes, scientists at the John Innes Centre are building a ‘triterpene machine’ which will enable them to custom-build valuable chemical compounds called triterpenes and produce them in large, cost-effective quantities.

    Using ‘chemical origami’ to generate customisable, high-value chemicals from plants.

  • Researchers of Kumamoto University in Japan have succeeded in the world’s first visualization of a peptidoglycan ‘wall’ present in the chloroplasts of bryophytes (moss plants). Until now, chloroplasts of green plants were considered to be surrounded only by two envelopes. The results of this research overturns conventional wisdom about the structure of chloroplasts.

    Hidden moss chloroplast ‘wall’ discovered.

    Any big surprises in the plant news from August 2016?

    To find out, “stay tuned”….

    HowPlantsWork © 2008-2017 All Rights Reserved.

  • From Very, Very Old Plants To New Uses For Plants

    It’s been an unusually cold winter here in the upper left-hand corner of the USA, so it’s pleasant to recall the warm days of June 2016.

    That month, the plant news topics ranged from ancient plants to new, exciting uses for plant biotechnology.

  • Scientists at Oxford University have discovered the oldest known population of plant root stem cells in a 320 million-year-old fossil. The cells, which gave rise to the roots of an ancient plant, were found in a fossilised root tip held in the Oxford University Herbaria.

    Scientists discover oldest plant root stem cells.

  • Farmers have monitored their fields for millennia by simply walking among the rows of plants, observing changes over time, and noting which plants do better.
    But as plant breeding technology becomes more complicated, farmers and scientists want specific data. They want to know exactly how tall the plants are, or exactly how green the leaves are In a large test field, getting exact numbers means hours or even days of labor for a plant breeder.

    A “Fit-Bit” for crop plants?

  • The genome of the corn plant – or maize, as it’s called almost everywhere except the US – “is a lot more exciting” than scientists have previously believed. So says the lead scientist in a new effort to analyze and annotate the depth of the plant’s genetic resources.

    “Amazing protein diversity” is discovered in the maize plant.

  • One of the new uses for plants is the production of vaccines and medicines. And here are two examples from June 2016.

    The fight against polio has been one of the great success stories of modern medicine, with the disease already eliminated in much of the world. However, current immunisation programmes use attenuated ‘live’ or ‘killed’ virus vaccines, both of which carry a risk of live virus escaping back into the wild.

    Plant-based vaccine among front runners in search for new polio jab.

    Tobacco, the plant responsible for the most preventable deaths worldwide, may soon become the primary weapon against one of the world’s deadliest diseases. Researchers have engineered tobacco plants to produce the chemical precursor to artemisinin, the best antimalarial drug on the market.

    Genetic engineering transforms tobacco plant into an antimalaria drug factory.

    We’re half way through the “greatest hits” of plant research news of 2016, and July produced one of the most surprising plant news stories of the year. Be seeing you….

    HowPlantsWork © 2008-2017 All Rights Reserved.

  • From The Current State of The World’s Plants To How Plants Conquered The Land

    May 2016 was an especially rich month for fascinating reports about plant research.

    So, let’s get on with it….

  • What is the current state of plants…on a global scale?

    A major report regarding this question was published by the Royal Botanic Garden, Kew.

    Kew report makes new tally for number of world’s plants.

  • Roses are red, violets are blue. Everybody knows that, but what makes them so? Although plant breeders were aware of some of the genes involved, there was as yet no quantitative study of how pigment turns a flower red, blue or yellow. Casper van der Kooi conducted just such a study, combining biology and physics.

    The anatomy of flower color.

  • Stem cells are typically thought to have the intrinsic ability to generate or replace specialized cells. However, a team of biologists at NYU showed that regenerating plants can naturally reconstitute their stem cells from more mature cells by replaying embryogenesis.

    Biologists Find How Plants Reconstitute Stem Cells.

  • Mathematical biologists love sunflowers. The giant flowers are one of the most obvious—as well as the prettiest—demonstrations of a hidden mathematical rule shaping the patterns of life: the Fibonacci sequence, a set in which each number is the sum of the previous two (1, 1, 2, 3, 5, 8, 13, 21, 34, 55, 89, 144, 233, 377, 610, …), found in everything from pineapples to pine cones.

    Sunflowers show complex Fibonacci sequences.

  • An almost entirely accidental discovery by University of Guelph researchers could transform food and biofuel production and increase carbon capture on farmland.
    By tweaking a plant’s genetic profile, the researchers doubled the plant’s growth and increased seed production by more than 400 per cent.

    Chance Finding Could Transform Plant Production.

  • Research at the University of Leeds has identified a key gene that assisted the transition of plants from water to the land around 500 million years ago.

    How plants conquered the land.

    Next Up: Plant news from June 2016….

    HowPlantsWork © 2008-2017 All Rights Reserved.

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