Controlling where gibberellin acts reveals how the plant hormone coordinates root growth
Plant hormones influence growth and development by acting on specific cells and tissues. However, determining precisely where and when a hormone needs to act has been challenging because conventional hormone treatment generally activates signaling throughout the plant.
Gibberellin (GA) is a key plant hormone that drives cell division and growth in both roots and shoots. Research has shown that activating GA signaling in the endodermis, a specific inner cell layer of the root, is essential for root elongation. However, the exact mechanism by which GA signaling coordinates growth across different root tissues has been unclear.
To address this question, researchers at Saitama University, Nagoya University, RIKEN, and HHU Düsseldorf developed a novel system that allows precise control over when and where GA activates its signaling pathway. By combining a synthetic version of GA with a modified receptor that only recognizes this synthetic form, the researchers could selectively activate GA signaling in targeted root cell layers.
They found that root elongation depends on the coordinated activation of GA signaling in both the endodermis and epidermis. While activating GA signaling in either layer alone promoted elongation, simultaneous activation in both layers produced a stronger response. Interestingly, the sites where GA was produced did not always match the areas where its signaling promoted growth.
Notably, a GA biosynthetic enzyme was identified in the cortex, even though activation of GA signaling in this layer did not result in enhanced root growth. This finding suggests that bioactive GA may be transported between cells from synthesis sites to signaling-responsive areas. The new synthetic GA-receptor system provides a powerful tool for manipulating plant hormone signaling with both spatial and temporal precision.
By enabling researchers to ask not only whether a hormone is required for a biological process, but also when and where its signaling needs to occur, this approach offers new insights into the complex coordination of hormone signaling across tissues. Understanding these spatial patterns of hormone action could lead to strategies for tissue- or organ-specific control of plant growth, with potential applications in improving crop yields and optimizing cultivation practices.
The study, published in Nature Plants, demonstrates how synthetic biology can be used to dissect the intricate regulation of plant growth and development by plant hormones.
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