To investigate where gibberellin signalling acts within a root, the researchers developed a synthetic gibberellin, sGA, that exhibits little or no binding to the plant’s endogenous receptor GID1. They also engineered a modified receptor, mGID1, that selectively recognizes sGA. Together, the two components allowed the researchers to activate gibberellin signalling in selected cells in living plants.

In the normal pathway, bioactive gibberellins bind GID1, promote the degradation of DELLA regulatory proteins and activate transcriptional programmes that influence cell division and elongation. Previous work had established that gibberellin signalling in the root endodermis is important for promoting root elongation, but the contributions of other root layers had remained unclear. By targeting the sGA–mGID1 system to individual tissues, the study separated the effects of signalling in the endodermis, epidermis and cortex.

The coordinated action of the endodermis and epidermis was required for the full elongation response. By contrast, gibberellin signalling in the cortex alone was insufficient, demonstrating that activation in one root layer could not replace the contribution of the layers that together produced complete root elongation. The researchers also examined the spatial pattern of gibberellin signalling and the distribution of biosynthetic components along the root.

Signalling and the enzymes involved in gibberellin biosynthesis showed a distal distribution, with GA3ox-expressing tissues positioned away from the principal sites of action in the endodermis and epidermis. These observations support a model in which bioactive gibberellins are transported from GA3ox-expressing regions to the endodermis and epidermis, where their combined action coordinates root elongation. The reported evidence is consistent with this transport model, based on the observed locations of signalling and biosynthetic components, rather than a direct demonstration of every step in the proposed route.

Beyond its role as a biological model, the sGA–mGID1 system provides a way to examine hormone signalling with cell-specific resolution. Because sGA is weakly recognised, if at all, by endogenous GID1 while mGID1 detects it selectively, the pair can be used to compare the consequences of activating a developmental pathway in different tissues. The authors describe the platform as a potentially versatile tool for synthetic control of processes such as root–shoot growth balance and for advancing plant synthetic biology.

Its demonstrated contribution is a controllable experimental system for resolving how the spatial arrangement of gibberellin signalling relates to coordinated root elongation.

Subject of Research: Cell-specific gibberellin signalling in the regulation of Arabidopsis root elongation

Article Title: Synthetic activation of gibberellin signalling reveals spatial coordination of root growth

Article References: Yagami, Y., Yamada, R., Ishikawa, Y., Meguro, E., Kusano, S., Itami, K., Frommer, W. B., Hagihara, S., & Nakamura, M. (2026). Synthetic activation of gibberellin signalling reveals spatial coordination of root growth. Nature Plants. https://doi.org/10.1038/s41477-026-02438-x

Image Credits: AI Generated

DOI: 10.1038/s41477-026-02438-x

Keywords: gibberellin signalling, Arabidopsis, root elongation, endodermis, epidermis, plant hormones, cell-specific activation, hormone transport, plant development, synthetic biology, Synthetic, activation