How plants 'muscle up' against bacteria in the cold

Michigan State University scientists have furthered our understanding on how a plant protein, called CAMTA, helps plants strengthen themselves as they anticipate long periods of cold, such as three to four months of winter in the American midwest or northern Europe.

The long-term goal behind the research is to breed or create plants with higher tolerance to wild swings in temperature. The study is published in the journal The Plant Cell.

CAMTA proteins are universally found across plants, and they help turn on genes that communicate freezing tolerance to these plants. In the study, CAMTA proteins were observed to also control how plants defend against harmful bacteria under long-term cold conditions.

In the cold, plants generally build up high levels of salicylic acid, or SA, a compound that protects them against bacteria.

"At warm temperatures CAMTA proteins, specifically the N-terminus (the start of the proteins), block the system that produces SA," said Yong Sig Kim, a post-doctoral student in the lab of University Distinguished Professor and MSU Foundation Professor Michael Thomashow.

When it gets cold for a long enough period, an unknown signal is generated that modifies CAMTA to allow SA production to turn on. In that case, the C-terminus, or the bottom of an amino acid chain that is stopped by a free carboxyl group, detects the signal -- possibly a rise in cellular calcium levels -- that enables SA biosynthesis.

This observation reverses current accepted models, which proposed instead that the C-terminus blocked SA production.

Why does tolerance to the cold instigate bacterial defenses?

"SA doesn't protect the plant from the cold, per se. Instead, we think the plants enhance their immune systems in the cold as a general preemptive strategy," Kim said.

Although plants take measures to survive the cold, they still get injured, and their structures are destabilized, which makes them more vulnerable to bacterial infection.

So, weakened plants keep their guard up as a precaution. It is similar to how humans take preventative measures to stay healthy – eat well, sleep eight hours, hydrate, etc.

This knowledge has long-term potential impact on agricultural production. For example, according to the EPA, in 2010 and 2012, high nighttime temperatures affected corn yields across the U.S. Corn Belt, and premature budding due to a warm winter caused $220 million in losses of Michigan cherries in 2012.

 "The field of plant defense is gradually revealing how protection mechanisms against the elements and against other living beings are interrelated," Kim said.

Will winter's bitter cold damage plants?

The new year is arriving in a blast of bitter cold. People can snuggle indoors where it's warm, but what about plants? Will the harsh weather do them harm?

"For plants that are fully dormant, there shouldn't be any problem," said Sharon Yiesla, plant knowledge specialist at The Morton Arboretum in Lisle. Dormancy is the resting state that plants enter to protect themselves against winter cold and drought.

The aboveground parts of trees and shrubs have bark to protect them. Buds at the tips of branches are shielded by bud scales. Perennials have allowed their stalks and leaves to die back already. Plants' roots are still alive, but they are safe in the ground. "As long as the roots are underground, they are protected," Yiesla said.

The main risk she sees is for evergreens, which may not have fully entered their dormant state because of warm weather in the fall. Evergreen needles retain some water all winter and could be dried out by bitter cold and wind.

"Depending on how long the cold goes on and how low the temperature falls, we may see a little more winter damage on evergreens than we sometimes do," she said. "But it won't be apparent until spring, and there's nothing a homeowner can do about it now."

The greatest danger isn't from cold, but from warm weather that can follow. Chicago often swings between cold and warm spells, and plants can be harmed by the quick shifts. When soil warms, dormant plants may start to wake up and then be hit hard by the next cold snap.

Plants with shallow roots, such as hydrangeas and hellebores, are especially vulnerable, along with species that are not quite hardy here, such as oakleaf hydrangea and butterfly bush.

"The best way to prevent damage from freeze-thaw cycles is to make sure there's a layer of mulch over the roots," Yiesla said. The mulch will insulate the soil, so it stays evenly cold.

You can use wood chips or fallen leaves, but another source of mulch is handy at this time of year: evergreen boughs. "Cut up your Christmas tree and lay the branches on the soil around vulnerable plants," she said. "They will help insulate the soil."

Be good to your house plants, they’ll be good to you

 Indoor plants are wonderful things. They are green and beautiful and even shiny, if you bother to dust the leaves or give them a bath now and then. House plants take in carbon dioxide and release oxygen, helping to clear the air and make the inside of your home a healthier place for you and your family. Indoor plants are especially nice to have around in the autumn and through the winter when the garden outside is often less attractive and accessible.

But at the moment I feel a touch guilty talking about house plants. A few weeks ago, I finally had to toss a rubber plant that had died, slowly and painfully, fallen brown leaf by fallen brown leaf. It was beautiful when I bought it and plunked it down on the raised hearth, on the wall farthest from the living room's largest window. It was big and gorgeous for several weeks, sitting in a large green pot, but then the leaves began to brown, curl and fall. Watching this lovely plant die was heartbreaking, but did I do any research to find out what was wrong? Unfortunately, no, until it was too late. That was when I discovered the poor thing wasn't getting enough light and was possibly getting too much water. I moved it into the dining room next to a window, but by then the die was cast.

Tossing that rubber plant was a rather expensive lesson in doing research sooner rather than later. I've had great luck with other house plants — mother-in-law's tongue, pothos, and various palms — and thought I knew what I was doing. But no. Googling “rubber plant” after I bought it would have saved me much grief, and my rubber plant might still be with us.

If you do a bit of research first, raising house plants and keeping them healthy isn't difficult. I've had some house plants for many years. I moved nine months ago, and it took a while to find the optimal spot for all of them. But here's the thing. With these plants, I paid attention to their ups and downs and responded accordingly. For some crazy reason, I had too much faith in that poor rubber plant to pay proper attention.

House plants do need different care from outdoor plants. They are highly sensitive to light levels, and less water is usually preferable to too much. But it is easy to find many indoor plants that thrive in many different light conditions and that conform to your personal plant care philosophy, whether it be to do everything on a carefully set schedule or on a more catch-as-catch-can basis.

For the catch-as-catch-can indoor gardener, the mother-in-law's tongue and pothos in my living room are the perfect solution. Mother-in-law's tongue, also known as the snake plant, does well in low light and is almost impossible to kill. It can be watered as seldom as once a month. The pothos vine likes a bit more light (I combined the two plants just for the photo), but it will signal when it needs water by starting to look limp and wilted. A good soaking in the kitchen sink will refresh it.

Children will enjoy the pothos vine because it is simple to create more plants. When a vine gets too long, just cut it off and put the cut end in a jar filled with water on a window sill. It will grow roots and can then be planted in a new pot. Where you had one plant, you now have two.

There are dozens of other indoor possibilities. The air plant is extremely easy to grow, and no soil is involved. Just soak each plant for two or three hours every ten days or so, and they will thrive on a saucer or dish on a counter or bookcase in indirect light.

Aloe likes indirect light and a good soak about once a week. Aloe also has excellent healing properties. If someone gets a burn in the kitchen, break a leaf open and smear the aloe sap on the burn.

Diffenbachia likes filtered light, perhaps by a curtained window. Spider plants like lots of light and a weekly watering. Peace lilies prefer indirect light. They are another plant that lets you know when it needs water. African violets are lovely in a kitchen window.

Palm trees are often easy to grow indoors and may remind you of sunnier climes in the depths of winter. The parlor palm prefers low light and may suffer if exposed to direct sunlight. It grows very slowly and may take years to reach its full height of three to four feet. I have had great luck with the Kentia palm. In its native habitat, it can reach 60 feet. But indoors it tops out at 6 to 12 feet. This plant benefits from periodic soaking in a bucket or deep sink to thoroughly wet the entire root ball.

Orchids are another winter delight. I avoid them in the summer when I'm running ceiling fans because the plants dry out.

Of course nothing beats a Christmas cactus at this time of year. Give it indirect light and occasional water, and its festive color will brighten your holidays into the new year.

Meet the Overcompensators, Plants That Get Tougher and Meaner When Attacked

If plants could be stars in a cowboy film, the scarlet gilia would be one of the meanest wildflowers west of the Mississippi.

You can find it standing tall among the sagebrush on mountainsides, its red flowers blazing. Drought can't always stop it. Shade won't faze it. And when mule deer and elk start grazing on it early in the season, it comes back bigger and stronger, with more defenses and a posse of new plants.

Biologists call outlaw plants like this the overcompensators.

“It's a little counterintuitive,” said Miles Mesa, a graduate student at The University of Illinois, Urbana-Champaign who led a new study into these types of plants. “After some animal comes by and eats it, the plant actually does better.”

In the study published this month in the journal Ecology, scientists showed for the first time that in an experiment, damaging some plants set off a molecular chain of events that caused them to grow back bigger, and produce more seeds and chemical defenses simultaneously. At the genetic level, the two tactics for plant survival worked hand in hand — at least in Arabidopsis thaliana, a kind of mustard plant often used for research.

Ken Paige, an evolutionary ecologist also at he University of Illinois and principal investigator of the study, first observed overcompensation in the scarlet gilia in 1987. He described plants that would make more flowers, stems and seeds when their main stems were cut off or eaten.

At the time, being eaten was believed to be bad for plants — always. It took a decade's worth of seeing the contrary for other biologists to believe it.

Dr. Paige started looking for a molecular mechanism behind overcompensation in some versions of Arabidopsis. As he damaged their main stems, he started seeing indications that not only did they get bushier and produce more seeds, but they also ramped up their chemical defenses.

At one point in time, theory pitted regrowth, also known as tolerance, against defense: with limited energy, a plant had to pick one or the other.

But in the past decade, more researchers can't find a trade-off, said Anurag Agrawal, an ecologist at Cornell University who studies plant-herbivore interactions and was not involved in the study.

Dr. Paige thinks a special process at the molecular level helps plants that overcompensate employ both strategies.

Most plants respond to damage with a process called endoreduplication, in which a cell can copy its DNA over and over without splitting into two cells. This gives the plant bigger cells with multiple energy factories to accomplish a variety of tasks. Many damaged plants only show minimal levels of endoreduplication. But the overcompensators go into overdrive with the process.

In the case of the study's mustard plants, they were able to grow bigger and also produce glucosinolate, the sulfurish, bitter chemical compound in mustard, kale, cabbage and horseradish.

And the new research finds that when it comes to building up tolerance or defenses, for at least some plants, you can't have one without the other.

“What this paper shows is that, in practice, defense and regrowth actually go hand-in-hand because the genetics of defense and regrowth are similar,” Josh Banta a biologist at The University of Texas at Tyler, who was not involved in the study. “Like it or not, theory be darned.”

But even the baddest cowboys are not immortal, the researchers found. If they cut the main stem and 75 percent of its leaves, even overcompensators can't rebound.

This tough guy tactic may be a special case, said Dr. Agrawal, but Mr. Mesa and Dr. Paige think it could be generalized to many other plants. Depending on much that turns out to be true, future research could one day help farmers grow super crops that made more food without having to use as many pesticides. But as the story often goes for basic genetic research on crops, results that could be applied are a ways off.

Ecuadorians prefer non-native plants for medicinal use

 

The beautiful frailejón plant (Espeletia pycnophylla Cuatrec., Asteraceae) in the páramo region of northern Ecuador during a visit by author Georgia Hart. Frailejón is utilized in multiple ways for medicine including in the treatment of arthritis, earache, headache, deafness and prevention of hair loss. Photo credit: Neagha Leonard.

Plant medicine is practiced widely across the world, however, there is concern that introduced plants could be replacing the use of native plants for medicine in various regions. It is critical to understand the potential influence of introduced plant use on native plant treatments. With hundreds of thousands of native plant treatments used by indigenous peoples worldwide that have yet to be fully examined, there is a likelihood that cures for many common maladies such as hair loss, arthritis, dementia and even cancers might already exist. This research provides valuable information for possible approaches to preserving that rich cultural knowledge.

To better understand why people select non-native plants for medicine, Georgia Hart, a PhD student in the Department of Botany at the University of Hawaiʻi at Mānoa, led a group of international ethnobotany researchers on a bioinformatics project focused on medicinal plant use in Ecuador.

The team studied the use of introduced, or non-native, plants for medicine in Ecuador, using a bioinformatics approach to generate new understanding in ethnobotany by synthesizing information from two large databases. The first database, The Catalogue of Vascular Plants of Ecuador, includes more than 17,000 plant species. The Catalogue of Useful Plants of Ecuador is a compilation of more than 40,000 recorded medicinal plants uses, accrued over centuries.

Ecuador is one of few megadiverse countries in the world. It is also highly culturally diverse with more than 17 ethnic groups and languages spoken. Use of plant medicine is common in Ecuador, including among the mestizo, or racially mixed, population. This context and these databases provided an ideal repository of information for the international team.

hat the authors found was that introduced plants are selected much more often for medicine than would be predicted based on their abundance. Why was this the case? The availability of introduced plants was important in their selection, mostly as it relates to cultivation. Introduced plants also tended to treat illnesses that few native plants treat. Finally, introduced plants, on average, treated more conditions than native plants. It therefore appears that introduced plants are sometimes selected in ways that could supplant native plant use. The strong correlation between medicinal use of plants and cultivation suggests human-mediated environments such as home gardens and agroforests should be protected for the valuable human health resources they provide in Ecuador.