Getting a grip on plant anchor roots

Now, researchers including Kun-Peng Jia and Salim Al-Babili of King Abdullah University of Science and Technology (KAUST) have found that anchor root formation is triggered by a signalling molecule derived from carotenoids, common pigments that give plants their colour. 

Named anchorene, the molecule belongs to a set of compounds known as diapocarotenoids, which had so far been viewed merely as metabolic intermediates, or precursors, of biologically significant molecules. Anchorene is “quite unstable and difficult to detect,” explains Jia, the study’s first author. Jia and his colleagues had previously developed a screening system to identify known and predicted diapocarotenoids, leading to their identification of anchorene in 2018.  

Using Arabidopsis as a model plant, the team demonstrated that anchorene has the exact chemical signal needed to promote anchor root development. Through transcriptome studies, involving analysis of coding and non-coding sequences of RNA, they showed that anchorene induces anchor root formation by modulating the activity of auxin, a well-known plant hormone that stimulates growth and development.

"Anchor roots … have received less research attention until now,” says Takaki Yamauchi, a plant molecular geneticist at the University of Tokyo, who was not involved in the study. “Jia et al show that anchorene triggers anchor root formation by modulating auxin homeostasis. Now is the time to take notice of this lesser-known fourth type of root."

The researchers also tested the effects of nitrogen deficiency on root growth. They observed an increase in anchorene levels and anchor root numbers, suggesting it plays an important role in how Arabidopsis responds to harsh conditions.

They also examined the effects of anchorene on rice roots and found “a notable induction in root length, indicating the potential of this metabolite in promoting plant growth,” the researchers write in their study published in Science Advances. 

“Anchorene changes the root architecture by promoting anchor root formation, which increases plant root volume and facilitates water and nutrient absorption,” says Jia. He notes that anchorene is already “commercially available and used in the manufacture of different carotenoids on an industrial scale, which makes its application to agriculture quite feasible.” 

The team aims to uncover the in-depth mechanism of how plants produce anchorene and will continue to study its biological activity in other plant species, particularly in crops.

Their findings may stimulate further research into other carotenoid-derived signalling molecules. 

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