In the early 2020s, Hebrew University scientists edited 2 tomato genes involved in flower development and fertilization. Now, the plants can produce seedless fruit without fertilization and deliver more than 18 times as many fruits early in winter

Tomato gene editing: A tomato has to pass through several stages before it becomes fruit. Its flower must develop properly, pollen needs to be released at the right time and fertilization has to take place. When temperatures fall, that process can become harder, leaving plants with few or no fruits.

Researchers at Hebrew University have identified a genetic system that helps coordinate these stages of reproduction, as per a report. By editing two closely related tomato genes, they produced plants capable of forming fruit without fertilization and saw a dramatic increase in fruit production during the early winter growing season, as per an EurekAlert report.

In greenhouse experiments, the edited plants produced more than 18 times as many fruits as regular tomato plants early in the growing season.

Two genes help coordinate tomato flower development

The study was led by Prof. Naomi Ori and doctoral researcher Nave Man at Hebrew University, together with researchers from the Leibniz Institute of Plant Biochemistry in Germany and Israel's Agricultural Research Organization, also known as the Volcani Institute.

The team focused on the plant's response to auxin, a hormone involved in growth and reproduction. Within this system, some factors promote the auxin response, while a small regulatory RNA called miR167 acts as a brake.

Researchers used CRISPR gene editing to alter genes within this system and examine how the changes affected flower development and fruit production.

They found that two closely related genes, SlARF8A and SlARF8B, work together to coordinate the development of the male and female reproductive organs in tomato flowers, according to the EurekAlert report.

One of the genes also helps control when the flower's anthers open and release pollen, an important step in successful fertilization.

The edited tomatoes could form fruit without fertilization

The most striking result came when researchers altered both the promoting and restraining parts of the genetic system.

The edited plants were able to begin developing fruit without fertilization through a natural process known as parthenocarpy. The resulting tomatoes were seedless.

The plants also began producing fruit earlier under all the conditions tested. The difference became particularly noticeable during cold winter conditions, when regular tomato plants produced little or no fruit.

In winter greenhouse experiments, the edited plants produced more than 18 times as many fruits as the regular plants early in the growing season.

The difference continued through harvest

The advantage was not limited to the beginning of the growing season.

By harvest, the gene-edited plants had produced six times more ripe tomatoes and 10 times the total weight of ripe fruit compared with the regular plants.

Most of the tomatoes on the edited plants had already ripened and turned red by the end of the experiment. On the unmodified plants, most of the fruit remained green.

The edited plants were also more compact, directing more of their energy toward fruit production rather than stems and leaves.

Why the genetic changes matter in cold weather

Normal tomato reproduction depends on several events happening in the right sequence. The flower's reproductive organs must develop, pollen needs to be released at the appropriate time and fertilization must occur before normal fruit production.

Temperature extremes can interfere with that sequence. Cold conditions can reduce pollen viability and make fertilization more difficult.

The gene-edited plants bypassed the need for fertilization by producing fruit through parthenocarpy.

Prof. Ori said, "Our findings show how tomato plants use a carefully balanced genetic system to coordinate flower development, pollen release and the beginning of fruit growth," adding, "Understanding this system may eventually help us develop crops that produce fruit more reliably when temperatures make normal fertilization difficult," as quoted by EurekAlert.

The research could help tomatoes grow through colder months

The findings may eventually help extend tomato production into colder seasons and make winter harvests more stable.

The approach could also be useful for tomatoes grown for processing, where seedless fruit and reduced jelly content can be advantageous.

But the edited plants are not yet ready for commercial use. More research is needed to determine how the genetic changes affect fruit size, flavor and overall quality, as well as whether the changes can be successfully introduced into agricultural tomato varieties.