Recognizing others but not yourself: new insights into the evolution of plant mating

How plants evolve diversity in the genes that prevent self-fertilization.

The stigma of Petunia contains a toxin that stops pollen growth. Pollen in turn has a team of genes that produce antidotes to all toxins except for the toxin produced by the
The stigma of Petunia contains a toxin that stops pollen growth. Pollen in turn has a team of genes that produce antidotes to all toxins except for the toxin produced by the "self" stigma. © Lewis Collard

Self-fertilization is an issue, as it prompts inbreeding. Recognition systems that anticipate self-treatment have advanced to guarantee that a plant mates just with a genetically extraordinary plant and not with itself. The recognition systems underlying self-incompatibility are discovered surrounding us in nature and can be found in no less than 100 plant families and 40% of species. As of not long ago, notwithstanding, scientists have not known how the astonishing diversity in these systems evolves.

group of scientists at the Institute of Science and Technology Austria (IST Austria) has influenced projects towards disentangling how new mating types to advance in non-self-recognition self-incompatibility systems, prompting the staggering genetically assorted variety found in nature. The outcomes are distributed in the current month’s release of Genetics.

In plants such as snapdragons and Petunia, when the pollen lands on the stigma, it germinates and starts growing. The stigma, however, contains a toxin (an SRNase) that stops pollen growth. Pollen, in turn, has a team of genes (F-box genes) that produce antidotes to all toxins except for the toxin produced by the “self” stigma.

Therefore, pollen can fertilize when it lands on the stigma that does not belong to the same plant, but not when it lands on the plant’s own stigma. It may seem like a harsh system, but plants can use this toxin-antidote system to ensure that they only mate with a genetically different plant. This is important as self-fertilization leads to inbreeding, which is detrimental for the offspring.

In non-self recognition systems, the male (pollen) and female (stigma) genes work together as a team to determine recognition, so that a particular variation of the male- and female-genes forms a mating type.

Non-self-recognition systems are discovered surrounding us in nature and have a bewildering decent variety of mating types, so the big question in their advancement is: how would you develop another mating compose while doing as such requires a mutation in the two sides?

For example, when there is a change in the female side (stigma), it produces a new toxin for which no other pollen has an antidote – so mating can’t occur. Does this mean that there needs to be a change in the male side (pollen) first so that the antidote appears and then waits for a corresponding change in the stigma (female side)? But how does this co-evolution work when evolution is a random process? Is there a particular order of mutations that are more likely to create a new mating type?

To decipher how such complex non-self recognition systems evolved, Melinda Pickup, a postdoc in the group of Nick Barton at IST Austria and experimental plant biologist, worked together with theoreticians (and previous postdocs in the Barton group) Katarina Bodova, now Assistant Professor at Comenius University in Bratislava, Tadeas Priklopil, now postdoc at the University of Lausanne, as well as David Field, now Assistant Professor at the University of Vienna.

Nick Barton said, “This project shows how collaboration between scientists with very different backgrounds can combine biological insight with mathematical analysis, to shed some light on a fascinating evolutionary puzzle.”

Through hypothetical examination and simulation, the scientists researched how new mating types can advance in a non-self-recognition system.

They found that there are diverse pathways by which new composers can develop. Now and again this occurs through a halfway phase of having the capacity to self-treat; however, in different cases, it occurs by remaining self-inconsistent. They likewise found that new mating types just advanced when the cost of self-preparation (through inbreeding) was high.

Being inadequate – i.e., having missing F-box qualities that deliver remedies to female toxins – was observed to be essential for the development of new mating types: finish mating composes (with a full arrangement of F-Box qualities) remained around for a very long time, as they have the most noteworthy number of mating accomplices.

New mating composes developed more promptly when there were less mating types in the populace. Additionally, the socioeconomics in a populace influences the development of non-self-recognition systems: populace size and transformation rate all impact how this system advances.

So although it seems like having a full team of F-box pollen genes (and therefore antidotes) is the best way for new mating types to evolve, this system is complex and can change via several different pathways. Interestingly, while the researchers found that new mating types could evolve, the diversity of genes in their theoretical simulations were fewer compared to what is seen in nature.

The results are published in this month’s edition of Genetics.