Binding P’s and Q’s, Minding T’s and I’s

When it comes to nailing down the location of P and Q in plant Photosystem II, you have to be careful how you cross your t’s and dot your i’s.

A longstanding question in the area of Photosystem II research involves the complement of proteins on the lumenal side of the enzyme in plants vs. cyanobacteria. This region of the complex serves to split water into molecular oxygen- a seemingly conserved reaction in all oxygenic photosynthetic organisms. However, it has long been known that the extrinsic proteins associated with the lumenal face of the complex differ significantly between plants and cyanobacteria.

Differences in the lumenal extrinsic proteins, plants vs. cyanobacteria

Differences in the lumenal extrinsic proteins, plants vs. cyanobacteria

Studies from various disciplines in recent years (structural, mutants, proteomic) have layered on more questions. Biochemical work on plants indicates there are three extrinsic proteins- PsbO, PsbP and PsbQ. Biochemical analysis and structural studies of cyanobacteria have shown that their PSII complexes contain PsbO, PsbU and PsbV. Other proteomic analysis and mutant studies have shown that cyanobacteria also contain homologues of PsbP and PsbQ (aka CyanoP and CyanoQ, respectively). Sure, this accumulation of data sounds like alphabet soup to those outside of our field, but it also leaves photosynthesis researchers wondering how appropriate it is to use structural information from cyanobacteria to infer anything about PSII structure in plants.

For all the knowledge we’ve gained, we’ve been comparing green apples to blue-green oranges. New research from the Bricker lab has used chemical crosslinking and mass spectrometry to gain more information on the organization of extrinsic proteins in plant PSII- directly from plant material. I’ve written about these techniques before in another paper addressing a similar problem from the cyanobacterial extrinsic protein vantage point. In a publication available electronically this week, Mummadisetti et al provide new information on the arrangement of the PsbP and PsbQ proteins in higher plant PSII. This work goes beyond what either of the individual protein crystal structures (not in the context of the PSII complex) could tell us. Distance constraints from the crosslinking data were used to guide modeling studies to fill in gaps in the solution structure of PsbP as well as identify interaction sites with PSII membrane components and another extrinsic protein, PsbQ. Altogether this gives us a more complete picture of an important enzyme.

In addition to the satisfaction that comes with publishing this great work in a top journal, the authors have also been featured in a research highlight by the university. Since I like to take things a step further on this blog, this post will feature the behind the scenes story of how this project came to be a publication worthy of a press release- especially with regard to how the story is told with imagery.

As is typical of any press release, an image is used to capture the essence of the research. In the featured image, we see Manju Mummadisetti without lab coat and gloves, holding her PSII membranes proudly aloft the pristine ice bucket next to a carefully positioned bag of spinach leaves that have yet to meet their demise in the Waring blender. I get it. In photosynthesis research labs we always have a tube or bubbling flask of something green-ish that easily fits the stereotype non-scientists have of what scientists must do all day long. Every. Day.

Credit: Louisiana State University

Credit: Louisiana State University

Long time readers of this blog will realize that in this image Manju is breaking the first rule of biochemistry. Fast. And. Cold. No self-respecting biochemist would gaze longingly at their biochemical sample that wasn’t on ice or in the cold room. Moreover, photosynthesis researchers opt for darkness or dim light for their preparations in order to keep activity low and avoid damage. I can say unequivocally that Manju knows and obeys all of the rules of biochemistry. This sample was only for practice or for show. A more true picture would look like this.

What real research looks like

What real research looks like

Notice the lab coat and gloves. Samples are kept in the ice bucket. For all you know, there’s nothing in there at all green or otherwise.*

Manju spent considerably more time gazing at data on her computer screen than she ever did her green samples. In the picture below, she is analyzing mass spec data and evaluating the validity of calls made by the software. p > 0.005 need not apply for her results, but anything better is painstakingly recorded on a brown paper towel.


But really, Manju’s research is more appropriately captured in other images like this one.

It's harder than you think

It’s harder than you think

It may not make for click bait, but carefully filling out FedEx shipping forms is an essential part of her research. After Manju prepares her samples, they must be shipped overnight on dry ice (Fast. And. Cold.) to collaborators in Cincinnati for the mass spectroscopy analysis. These shipments are carefully planned so that someone is available to receive them and perform the analysis. This isn’t always easy over the summer when it is necessary to coordinate the travel schedules of half a dozen researchers in two different labs.

On one such occasion, forms and labels were not filled out appropriately. Not because Manju forgot to dot and i or cross a t, but because she did. Packages with dry ice require a special hazard label that must include all address information for both the sender and recipient in a very small area. We never knew how critical it was to avoid crossing that dotted line of the diamond.**

Notice how the last 'ti' in Manju's name infringes into the label

Notice how the last ‘ti’ in Manju’s name crosses over the dotted line and into the hazard label. Such a distraction could interfere with proper handling of this hazardous substance.

IMG_0038 (2)

Really FedEx? Her name is 20 characters long! Plus, the all caps just makes it seem like they’re yelling. It’s that serious.

A diligent FedEx employee at the Baton Rouge office rejected the shipment and sent it back to the lab at LSU the next day. I know rules are rules, but really this is on the verge of Gas Station Manager Syndrome. The samples were fine and promptly placed back in the freezer. A flurry of NSFW text messages about the situation were exchanged among people still on vacation. A new shipment date was coordinated and new forms were completed. It went away without a hitch and was promptly turned into data.

A new lesson was learned that day- Thou shalt not write within the dotted line of the hazard label. It’s an extension of a long-standing research rule- Obey arbitrary formatting and paperwork requests from people that control what you need.



*Full disclosure- there was NO sample in that ice bucket. No one in the lab had any membranes prepped that day and real biochemists don’t pull good samples out of the freezer for a photo op.

**It’s like crossing the streams in Ghostbusters apparently. It would be bad.

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Plant Skulls

snapgdragon seed pod skull dragons skullIf you didn’t know this was a plant science blog, you might think these were macbre trophies of some ancient tribe. This isn’t so much an appropriate plant costume for Halloween as it is an interesting confluence of floral anatomy and human propensity for recognizing facial forms.

Snapdragons or Antirrhinum sp. are a colorful staple of summer gardens. We’re more used to seeing them look like this image with tall inflorescences boasting clusters of ruffled flowers in a variety of color schemes.

Antirrhinum majus Credit: Michael Apel via Wikimedia Commons

What’s responsible for this spooky transition from delicate flowers to haunting faces? It all comes down to the snapdragon’s flower structure and its bilateral symmetry. The skulls are really the seed pods of the plant after the flowers have been pollinated and the petals have withered away. Dissecting the flowers in their prime shows the ovary at the base of the bloom. The pollen-containing stamens and the style emerge from the orifices in the ovary. These structures leave behind gaping holes that look like a mouth and eye sockets.

Snapdragon flower anatomy

Snapdragon flower anatomy

The striking resemblance of these seed pods to human skulls has led to their association with supernatural powers. They were purported to help women stay young and beautiful as well as protect humans of all ages from witchcraft and evil spirits. I don’t have any scientific evidence of that, but if you’re looking for new ideas for botanical Halloween decorations that go beyond cucurbits and mums, dried snapdragon stems with seed pods make a wicked wreath.


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Flying Duck Orchid

Caleana major off the Elvina Track, Ku-ring-gai Chase National Park, Australia Credit: Peter Woodard via Wikipedia

Today’s featured floral form is Caleana major, an orchid from Australia. It looks like a duck. It flies like a duck when the wind blows, but it’s just a flower. Why would an orchid develop such an elaborate costume? The answer is again pollination.

While this may look like yet another case of autotroph posing as heterotroph, it’s not the one you think. Caleana major’s flowers are designed to attract male sawflies. When the flies enter the larger ‘body’ portion of the flower, the ‘neck and head’ portion of the flower snaps closed behind them. For about a minute or so, the sawflies buzz around in a slight frenzy and become coated in pollen. This ensures that flower pollinates itself and any pollen remaining on the fly travels with it to the next flower.

Closed Flying Duck Orchid Credit: Peter Woodard via Wikipedia

The secret to this strategy is the sensitive ‘neck’ strap of the flower. This portion can sense when a fly has landed within the bottom part of the flower and trigger a response to have the ‘head’ snap closed. This trigger must also be reversed on a relatively short timescale to release the captive fly. He just needs enough time to be coated in pollen but none the worse for wear (unlike other carnivorous plants that intend on killing their insect victims with triggered mechanical responses).

This is an painting of Caleana major by Ferdinand Bauer, based on a drawing by him of material collected at Sydney in September 1803. It first appeared as Plate 8 in Stephan Endlicher’s 1838 Iconographia. It was scanned from Plate 13 of Mabberley, D. J. (1984) Jupiter Botanicus. via Wikipedia

There must be some interesting biochemistry underneath that response, not to mention the developmental gymnastics that must occur to make flowers that look like flying ducks. I’m not sure scientists will figure out these tricks because Caleana major cannot be cultivated outside its native environment. Because of its novel form and potential popularity with orchid enthusiasts, experienced growers have tried to grow it under greenhouse conditions, but with little success. It is speculated that a symbiosis with another microorganism in the soil of its native habitat is necessary for growth.



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Some floral forms make you wonder if they know something we don’t. Take Calceolaria uniflora for example.

When photographed at just the right angle, these slipper-shaped blooms look like the face of an alien wearing beats headphones and holding an empty white tray as a peace offering. Calceolaria is native to the southernmost portion of South America in Tierra del Fuego whose rocky alpine terrain could also be confused with an inhospitable planet in another solar system.

Cacleolaria uniflora Credit: Butterfly voyages serge Ouachée via Wikimedia

If it isn’t an orange alien, what exactly are we looking at? The stalk-like eyes are the stamens, which contain the pollen-producing anthers at the end. The petals of the flower are asymmetrical such that there is a large lower lip and a much smaller upper portion. The green sepals are even larger than the upper part of the petals giving the illusion of halo or headset. The lower lip of the slipper contains a prominent folded appendage in white, a striking contrast from the other features.

Calceolaria uniflora colony Credit: Thomas Mathis via Wikimedia

The purpose for this elaborate costume isn’t mimicry, it’s attraction. But they are phoning home for E.T., they’re setting the table for birds. Birds are a part of many plants’ reproductive strategies and it’s usually in the form of oil and nectar producing floral structures that entice hummingbirds and other small birds over for a drink. Even other Calceolaria species produce nectar for their bee pollinators, but not C. uniflora. In this case, the white tray and larger lower lip of the flower are edible. Birds eat the tray and slipper portion of the flower while the upper portion dusts the top of their heads with pollen. As the birds move from flower to flower, pollen is transferred as well.

Calceolaria uniflora with missing trays Credit: Javier Martin via Wikimedia

There are many other examples of plants using edible portions of themselves in their reproductive strategy. Seed dispersal by the animals that eat them is the whole point of fruit. However, the case of C. uniflora, where the plant offers up part of itself as a meal before seed production seems out-of-this-world risky to me.



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Dracula (Orchids)

Dracula radiosa Credit: Eric in SF via Wikimedia

If you thought we were done talking about plant costumes, you were wrong. While the title may lead you conjure images of vampires with fangs and dark cloaks, orchids of the Dracula genus look decidedly like something else- an adorable monkey face! I admit it’s a strange nexus of nomenclature and form; nevertheless, today’s post will be appropriate for all audiences.

Dracula simia Credit: Dick Culbert from Gibsons, B.C., Canada via Wikimedia

Dracula orchids won’t be found in Transylvania. These blooms are native to the cloud forests of Ecuador, growing in rainforests at elevations of ~3000 – 6500 feet. They were given their name by botanist Carlyle Luer in 1978. The name was inspired by the dark burgundy to black petals that curve up like the stiff collar of a vampire’s cloak. The petals also taper off into sharp points reminiscent of infamous vampire fangs.

Dracula vampira Credit: Eric Hunt via Wikimedia

But back to the real costume, why would a flower need to look like a monkey? If you’ve been paying attention to the last few posts, you can probably guess that the answer has something to do with pollination. However, it’s not quite as obvious as the Orphys bee orchid connection- these flowers are not trying to entice monkeys over for pollen transfer. From what scientists have been able to decipher so far, these flowers aren’t really wearing a monkey costume so much as they are wearing a mushroom costume. Take a closer look at the floral structure posing as the monkey’s snout. These lightly colored and highly ridged structures look very similar to mushrooms found nearby on the rainforest floor. Check out this link with images for a close-up comparison.

Yes, a perfectly good autotroph in mycological masquerade. It’s not just looks either. Again, orchids dig deep into their biochemical repertoire to create a specialized perfume to go along with the visual effect. All of these smells and visual cues serve to trick small flies into coming to their flowers for pollination purposes. The flies prefer real mushrooms as a food source and place to lay their eggs, but are fooled by the Dracula orchids.

Still, this botanical mushroom costume looks an awful lot like a small monkey’s face. I don’t think scientists have completely uncovered all of Dracula’s secrets when it comes to floral form. Investigations are still underway to tease apart the factors of shape, coloration, and scent. Of course, it’s still possible that the rest of the costume isn’t exclusively for the flies. The faces may serve to deter other would-be herbivores from eating the plants. If you were an insect or another small mammal, wouldn’t you think twice before walking over for a bite if that face was staring back at you? I know I would.

Dracula cordobae Credit: Javier Martin via Wikimedia

If you’re interested in learning more about the ecology of cloud forests and the scientists that study it, check out the link below for a trailer for the Cloud Forest Project documentary film.



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Corpse Flower: The Living Dead

Corpse Flower Credit: U.S. Botanic Garden via Wikipedia

Today’s plant costume is an odiferous disguise instead of a visual one. Its common name is also appropriate for the Halloween season- The Corpse Flower. It only pretends to be dead by giving off a rank odor of rotting flesh when it blooms. Again the reason is pollination. This horrible smell to us calls to every beetle and fly around that supper’s on. While they root around in the tight dark spaces of the bloom trying to find a decent place to feed and lay their eggs, they become covered in pollen. These pollen-covered insects then fly off to another bloom to pollinate another plant.

This species, Amorphophallus titanum*, is also a superphotosynthesizer in the plant world. As you may have noticed from the pictures and videos, the blooms can be as large as 10 feet tall. This makes the corpse flower the world’s largest inflorescence. Notice I didn’t say flower. Ah, botanical anatomy semantics! The images may look like a giant flower with burgundy petals surrounding a central stigma on steroids. Not so. The ‘petal’ portion of the flower is actually a bract structure called a spathe (plant biology word of the day). The tall central feature is called a spadix (bonus plant biology word of the day), and it is this structure on which the true flowers of the plant (separate male and female flowers) are arranged. The entirety of this plant reproductive structure is the inflorescence and there isn’t a bigger one in the plant world. The world’s record for a corpse flower bloom is nearly 11 feet tall. After flowering, the plant then makes the world’s largest leaf structure. It may look a tree in its own right, but developmentally, it’s just a compound leaf.


* Grossly translated as giant misshapen penis. Yeah. Well, you’ve seen the pictures. Stay classy readers!

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Psychotria elata

Psychotria elata

Psychotria elata

Voluptuous lips might not be something you’d expect on a plant science blog*, but today’s featured plant Psychotria elata has them. This small tree native to South American forests is commonly called the Hooker’s Lips plant after the unique shape of its flowers. Check out more images in the video below.

You have to admit that these puckers would rival those of even Angelina Jolie, Jessica Rabbit, Jagger and that guy from The Rocky Horror Picture Show. Why would you have a flower shaped like a pair of hooker’s lips? As indecent as it may sound, it still comes down to sex. The distinctive shape and color of Psychotria elata’s flowers are perfect for attracting their pollinators. At this point you might be wondering ‘What kind of pollinator is attracted to that?’ Well, it isn’t lonely men; it’s hummingbirds and butterflies. The bright red color draws them in and the central pore is a perfect fit for their narrow beaks and proboscis.

It’s universal to wonder, ‘But are they real?’ As in Hollywood, in the botanical world, the truth is complicated. These red smackers are real plant structures, but they aren’t really flowers. The red lips are actually bracts or modified leaves like those of Poinsettias. They hide the much smaller true flowers within. Check out some of the last images on the video above or the links below. As the inflorescence matures, the mouth eventually opens up exposing the flowers inside like a tongue or uvula.**

Unfortunately, deforestation in Psychotria elata’s native range is threatening its survival. Let’s hope we won’t have to kiss this species goodbye.


*Well, recently on the blog we’ve had gumbo, drugs, interspecies bee-flower sex and now hookers. Admittedly not my most sophisticated week. Stay classy readers!

**The flowers themselves are quite small, pretty but not particularly memorable. It would be cooler if they were more hideous such that when the ‘mouth’ opened it would look like that scene from Aliens.

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