Comprehensive coverage

Protection from the plant

A new Israeli study reveals that the desert gorse, a common plant in Israel, releases a pungency that prevents many animals from eating it - but gives the bulbul birds a "medicine" that helps them digest its fruits. And: how is all this related to cancer prevention?

Nightingales and a friend eating rakfatan. Photo by Gil-Kopilevitz
The nightshade uses a complex defense mechanism to repel unwanted eaters - but gives the bulbul a "secret trick" that allows it to enjoy its fruits and spread it further. Photo: Gil Kopilevitz

Between plants and animals there is a constant love-hate relationship. On the one hand, many plants want animals to eat their juicy fruits, thus spreading their seeds far and wide through their feces. On the other hand, the plants don't want the wrong animals to eat them: for example, those who will also digest the seeds themselves and use the proteins in them to build their bodies, instead of these materials helping the next plant generation. Thus, throughout evolution, both plants and animals developed a complex and intriguing system of balances and brakes, centers of attraction and preventive measures, around the two most basic needs of all of us: food and reproduction.

A new Israeli study Illustrates the way in which such processes have developed and operate in the desert plant, which is common in Israel and especially loved by the well-known bulbul birds, and reveals that the plant uses a complex defense mechanism to repel unwanted eaters - but gives the bulbul a "secret trick" that allows it to enjoy its fruits and spread it further.

The desert hawkmoth (Ochradenus baccatus) is a plant that is common in the Arava and Negev. His bushes are relatively large and his fruits are white and resemble small grapes. The gorse is an unusual plant due to the fact that its fruits are full of juice - even though it grows in the desert, where the water is known to be A rare commodity. Various animals enjoy the fruits of the cranberry, including rodents and birds.

Like other plants, the gorse also "wants" its fruits to be eaten only by animals that will also spread its seeds. For this, he uses a unique trick. In the pith - the juicy and tasty part of the fruit - there are substances called glucosinolates, while in the seeds inside the fruit there is an enzyme (a protein that accelerates chemical processes) called myrosinase. When some animal chews the fruit, the pulp and the seed are crushed together, the glucosinolates and the myrosinase meet - and the combination creates a splash of pungent and unpleasant taste in the animal's mouth.

This is similar to the process that characterizes vegetables from the cruciferous family, such as horseradish, mustard or wasabi seeds, which are very close to cruciferous vegetables: if we just place them whole on the tongue we will not feel any spiciness, but as soon as we bite into them, chop them or cut them - the substances and the enzyme will meet, And the familiar pungency of these plants will appear.

"Nightingales eat everything"

The trick of the weevil does the job - and prevents various animals that spread it from also digesting its seeds. "About a decade ago, we showed that common spiny mice (desert mice) understand the hint - they eat the float around the seed and spit the seeds to the ground," says Prof. Yoram Gershman from Oranim College and the Institute of Evolution at the University of Haifa, in whose laboratory the new research was carried out. "When they are young, at first they try to eat the whole fruit - and learn very quickly that this is a bad idea."

While sparrows have front paws that allow them to hold the fruit and eat it in the appropriate way, birds, without hands, do not have this option - therefore they eat the whole fruit, for its pungency. As mentioned, a very common bird that is known for its fondness for carp is the yellow-bellied nightingale (Pycnonotus xanthopygos) - this despite the fact that she feels the unpleasant pungency of the fruit. "Nightingales eat everything," says Gershman. This is beneficial to both parties: the birds, who gain nutrition - and the plant, whose seeds the bulbuls spread far in their flight.

Benefits for regular customers

In the new study, which was conducted in Gershman's laboratory in Beit Margolin at Oranim College by Dr. Benny Trabalsi, Prof. Ado Itzhaki and Nimrod Steindel from the Department of Evolutionary and Environmental Biology at the University of Haifa and Dr. Mia Lalazar from the University of Haifa and which was published in the prestigious scientific journal Nature Communications, the researchers captured ten bulbuls : 6 from the southern region, who are very familiar with rakfatan - and in fact, they were captured while they were in the bush, and 4 from the area of ​​Beit Shan, where rakfatan does not grow, and they have not met it in their days. The researchers avoided performing invasive actions, and all the birds were released into the wild unharmed at the site of their capture at the end of the study.

The researchers fed the bulbuls from the two groups with four different "foods": banana - a sweet fruit loved by the bulbuls, banana with the juice of the pistachio nut, banana with pistachio seeds and banana with pistachio and pistachio seeds combined. According to the three birds, they compared the degree of digestion of the food between the birds from the north and those from the south.

The researchers discovered that in most of the different dietary options, there was no difference between the degree of digestion of the bulbuls from the north and those from the south - except for the one that included both the pulp of the fruit and its seeds along with the banana: the southern birds, who know their custard, digested about 90 percent of the portion (that is, 10 percent of it came out in the stool) - while the northerners to whom he is a stranger digested significantly less - about 80 percent. That is, the southern birds digested 12 percent more of the food. "For a bird that needs to look for food - this is a significant difference," says Gershman.

The trick of the weevil does the job - and prevents various animals that spread it from also digesting its seeds. Rakfatan fruits, photo: Benny Trabalsi
The trick of the weevil does the job - and prevents various animals that spread it from also digesting its seeds. Rakfatan fruits, photo: Benny Trabalsi

In the next step, the researchers examined the effect of the combination of the fruit float and the seeds on common digestive enzymes that play a central role in the gut of bulbuls - and found that the combination of the float and the seeds reduced the activity of the enzymes by almost half. This disruption of enzyme function explains why digestion is impaired in northern birds. However, it was still not clear: why did the southern birds digest the food without interruption?

"The bulbul is the same bulbul - it is unlikely that there is a genetic difference between the bulbuls that live in the north of the country and those that live in the south," says Gershman. "However, we realized that there could definitely be a difference in the composition of the gut bacteria of the bulbuls from the different locations - that is, inMicrobiome The intestine".

Probiotics to the bird

As a result, the researchers collected triplicates of the birds from the north and the south and examined the composition of their microbiome - and were able to find a striking difference between the two groups: it was discovered that in the intestines of the southern birds, which eat sardines, a bacterium of the species Pantoea agglomerans It is the most common - while in the northern ones, these bacteria do not exist at all. "After we fed the northern nightingales with rakfatan - the pantoa amounts in them jumped", says Gershman. "It was surprising, until we looked at the fruits of the rakfatan - and found that they have a lot of the same pantoa."

The trick of the weevil does the job - and prevents various animals that spread it from also digesting its seeds. Rakfatan fruits, photo: Benny Trabalsi
"We looked at the fruits of the rakfatan - and found that they have a lot of the same Pantoa." Photo: Benny Trabalsi

Beyond that, the researchers discovered that the products of the combination between the saffron's float and its seeds harm dozens of bacteria that live in the birds' guts - but actually cultivate pantoa. "When the birds eat their roe, they also eat the pantoa that is in it, and the spicy substance created by the combination of the float and the seed makes a 'selection' in their intestines in favor of the pantoa," says Gershman.

The researchers added pantoa to a paste that included a banana with a float and seeds of raccoon and served it to the birds, and found that with the pantoa combination, the northern birds digested the dish to a similar extent to that observed in their southern counterparts. In other words, the pantoa, which the southern bulbuls are regularly exposed to through their gills, functions as a "medicine" that the plant gives them and that helps them digest it. "Probiotics work," Gershman laughs.

In addition, it was found that when an animal eats the whole fruit, the germination of the saffron seeds is damaged by the pungent substance created by the combination of the float and the seed. However, when the bacterium is found and breaks down the pungent substance, the germination of the seeds is not affected. In fact, three different species are beneficial from the relationship This: the bird receives a lot of nutritious nutrition, the plant receives an efficient distribution of those of its seeds that are not digested, and the bacteria receives a convenient distribution and growth in the bird's intestine.

Between cancer and curiosity

Today, the research on the subject continues, and the researchers are trying, among other things, to understand the mechanism through which the pantoa "fight" the products of the encounter between the float and the sperm of the sardines ("We have evidence that they actually eat these products", says Gershman).

The products of the combination between the fluff and its seeds harm dozens of bacteria that live in the intestines of the birds - but actually cultivate the pantoa. Pantoa isolated from the three bulbuls, photo: Benny Trabalsi
The products of the combination between the fluff and its seeds harm dozens of bacteria that live in the intestines of the birds - but actually cultivate the pantoa. Pantoa isolated from the three bulbuls, photo: Benny Trabalsi

According to Gershman, the new research does deal with a field that may sound a little far from us - wild plants and the birds that eat them, but he emphasizes that research like this can actually relate to fields that are very close to us, due to the fact that the falcon belongs to the salpaim series - to which the cruciferous family also belongs. "There is a lot of talk about cruciferous vegetables and other plants from the salvia series as substances that reduce the risk of cancer," says Gershman. "The reason for this effect is probably that the same substances that create the spicy taste also activate defense systems in our body against free radicals - which are one of the causes of cancer."

Be that as it may, Gershman sees another and significant scientific importance to the new study: interest. "In the end, we as scientists are curious people, that's what moves us", he concludes.