Researchers Found That Tomatoes Have Their Own Parallel Universe

sonyakamoz - stock.adobe.com - illustrative purposes only
sonyakamoz - stock.adobe.com - illustrative purposes only

Researchers from Michigan State University have discovered something surprising about tomatoes. Apparently, the roots of tomato plants produce a special class of metabolites known as acylsugars.

Previously, these compounds were thought only to be found in the fuzzy hairs, which are called trichomes, that grow on tomato leaves and stems.

Acylsugars consist of sugar cores made up of fatty acid chains. They help defend against pests in tomato trichomes. The acylsugars in the roots are different from the ones found within the trichomes.

After conducting advanced analyses, the scientists determined that the predominant acylsugar in tomato roots featured a sugar core composed of glucose linked to inositol, as opposed to the sucrose core present in trichome acylsugars.

“What’s so remarkable about these specialized metabolites is that they’re typically synthesized in highly precise cells and tissues,” Rachel Kerwin, one of the authors of the study and a postdoctoral researcher at MSU, said.

To find out more about how root and trichome acylsugars are made, the researchers identified genes in tomato roots that closely resembled the known trichome acylsugar genes.

Then, they used CRISPR gene editing to remove the genes ASAT1 and a particular gene from the tomato roots, dubbed ASAT1-L. It was the cousin of the trichome gene ASAT1.

Tomato plants without ASAT1-L did not produce any detectable acylsugars in their roots, while the acylsugar levels of trichomes remained unaffected.

When ASAT1 was knocked out, the opposite was true. These results suggest that, over time, tomatoes developed to have two separate acylsugar metabolic pathways. One of the pathways was for the trichomes, and the other was for the roots.

sonyakamoz – stock.adobe.com – illustrative purposes only

Furthermore, the research team noticed that the root and trichome acylsugar genes were gathered close together on the tomato genome, a type of genomic organization known as biosynthetic gene cluster.

“Alongside the aboveground acylsugar pathway we’ve been studying for years, here we find this second parallel universe that exists underground,” Robert Last, the lead study author and a researcher at MSU, said.

ASAT1-L most likely emerged when the ASAT1 gene got duplicated. Once that happened, the two genes split off and specialized for roots and trichomes.

The scientists even examined tomato relatives and found that ASAT1-L and root acylsugars were present in some wild tomato species but not distant cousins such as eggplant.

This indicates that the ability to make root acylsugars was a more recent evolutionary development in the tomato family tree.

Currently, the exact purpose of root acylsugars is unclear. The underground metabolites are similar to trichome compounds, so perhaps they help tomatoes protect themselves against pests and pathogens that live in the soil.

Another possible function is that they aid in drawing beneficial microbes to the roots. Further studies are needed to shed light on their roles.

The findings were published in the journal Science Advances.

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Emily  Chan is a writer who covers lifestyle and news content. She graduated from Michigan State University with a ... More about Emily Chan

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