Experimental gene-edited plants began developing seedless tomatoes even when cold weather disrupted fertilization. In a greenhouse experiment, they out-performed control plants and produced more ripe fruit, but have not yet been tested as commercial varieties.
Researchers fromThe Hebrew University They identified a genetic regulatory system that coordinates the development of reproductive organs in the tomato flower, the release of pollen, and the onset of fruit development. A combined change in two components of this system allowed experimental plants to develop fruit without fertilization and continue to produce even in cold conditions, where normal tomato plants hardly set fruit.
The study, published in the journal New Phytologist, was led by Prof. Naomi Uri and doctoral student Naveh Mann from the Institute of Plant Sciences and Genetics at theagriculture at the Hebrew University. It was attended by researchers from the Leibniz Institute for Plant Biochemistry in Germany and the Agricultural Research Administration – Volcanic Institute.
Every tomato starts with a flower, but the journey from bloom to fruit depends on delicate coordination. The male and female reproductive organs must develop at the right rate, the anthers must open and release pollen at the right time, and the pollen must fertilize the eggs in the ovary. Cold can reduce the vitality of the pollen and disrupt fertilization, while previous studies have shown that extreme heat also impairs fruit set.
The gas and brake pedal of the Oxy system
The researchers focused on the system that mediates the plant's response toAuxinAuxin, a plant hormone involved in growth, development, and reproduction. The activity of auxin is not controlled by a single gene, but by a network of regulatory factors.
The research focused on two closely related genes, SlARF8A and SlARF8B, which produce auxin response factors. In contrast, a small microRNA molecule called miR167, which reduces their activity and serves as a kind of molecular brake.
through CRISPR The researchers created changes in five genes from the SlMIR167 family and two SlARF8 genes, and then examined how different combinations of the changes affect flower structure and fruit mummification.
The results showed that SlARF8A and SlARF8B work together to coordinate the development of stamens and bracts. In addition to their shared role, SlARF8B also has a unique role in regulating the opening of anthers and the release of pollen grains.
Fruits without fertilization
The most striking result was obtained in plants in which a change in SlMIR167a and the loss of SlARF8B activity were combined. This combination changed the balance in the system and allowed SlARF8A to act in a way that caused a rapid and early onset of fruit development without fertilization.
This phenomenon is called parthenocarpy. The fruits develop from the ovary even without a pollen grain fertilizing the ovule, and are therefore seedless.
The ability to bypass the fertilization stage became particularly significant under cold conditions. In greenhouse experiments in winter, the plants that underwent gene editing develop fruit, while the control plants produced very few or no fruit at all.
At the beginning of the growing season, the treated plants had more than 18 times more fruit than the control plants. It is important to emphasize that this does not mean that the final commercial yield increased 18 times: this is a figure measured at an early stage, when the control plants had hardly developed any fruit.
At harvest time, the prepared plants had six times more Tomatoes Ripeness, and the total weight of the ripe tomatoes was ten times greater than that measured on the control plants. Most of the fruit on the trimmed plants had already turned red, while most of the fruit on the untrimmed plants remained green.
The trimmed plants were also more compact. A greater proportion of their resources were directed towards fruit production, rather than stem elongation and leaf formation.
Not yet an agricultural variety
According to Prof. Uri, the findings show how a balance between auxin response factors and microRNA coordinates the development of floral organs, the release of pollen, and the onset of fruit growth. Understanding the mechanism may help in the future in developing varieties that will continue to set fruit when temperatures make normal fertilization difficult.
However, the plants tested in the study are experimental plants and not tomato varieties ready for commercial cultivation. Before the approach can be used in agriculture, it will be necessary to test how the changes affect fruit size, taste, texture, nutritional value, shelf life and overall quality.
The trait will also need to be introduced into different crop varieties and tested over several seasons and under varying field or greenhouse conditions. Lighting conditions, humidity, diseases, nutrient availability and temperature fluctuations may affect the outcome.
The development may be particularly suitable for tomatoes intended for industrial use. In these fruits, the absence of seeds and a smaller amount of the gel-like substance that surrounds them may be an advantage. However, this option also requires testing the quality of the fruit and its suitability for processing.
The research was funded by the German Research Foundation, the National Science Foundation, and the Ministry of Agriculture and Food Security.
Questions and Answers
What prevents tomatoes from producing in the cold? Cold can damage the vitality of the pollen and the fertilization process. Without proper fertilization, most tomato varieties will not start fruit set.
What did the researchers change? The researchers used CRISPR to modify components of the miR167–ARF8 system, which regulates the plant's response to the hormone auxin and the development of reproductive organs in the flower.
How were fruits formed without fertilization? A specific combination of mutations in SlMIR167a and SlARF8B caused parthenocarpy – the development of fruit without fertilization. The fruits formed in this way were seedless.
Is it possible to buy tomato seeds like this already? No. These are research plants. Further testing of the flavor, size, quality, shelf life, and performance of the trait in agricultural varieties and under commercial growing conditions is required.
More on the subject on the science website
- CRISPR technology reveals complex genetic traits in tomato plants
- Scientists have discovered a gene in tomatoes that increases yield and improves its quality
- Edit, domesticate, grow: CRISPR from the tomato's close approach to the field
- The bacteria that saves the salad
- Climate crisis reduces agricultural areas worldwide and in the Middle East
For the original publication: Opening the original publication
