This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: 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 an important plant hormone that promotes cell division and elongation and is involved in the growth of roots and shoots. Previous studies have shown that GA signaling in the endodermis, an inner cell layer of the root, is important for root elongation. However, how GA signaling in different root cell layers contributes to growth and how these signals are coordinated across tissues has remained unclear.
To investigate these questions, a research team led by Professor Masayoshi Nakamura of Saitama University and graduate student Yuichiro Yagami of Nagoya University, in collaboration with researchers at RIKEN and HHU Düsseldorf, developed a synthetic system that allows scientists to control when and where the plant hormone gibberellin (GA) activates its signaling pathway. The study was published online in Nature Plants under the title "Synthetic activation of gibberellin signalling reveals spatial coordination of root growth." The research group developed an artificial system that combines a synthetic GA (sGA), which is not recognized by endogenous GA receptors, with a modified GA receptor (mGID1) that specifically recognizes sGA. By expressing mGID1 in specific cell layers of Arabidopsis thaliana roots and applying sGA, they could activate GA signaling selectively in cells expressing mGID1.
Because the timing of sGA application can also be controlled, the system provides both spatial and temporal control of GA signaling. Using this system, the researchers found that root elongation requires coordinated GA signaling in two distinct cell layers, the endodermis and epidermis. Activating GA signaling in either layer promoted root elongation, whereas activation in the cortex was insufficient to promote elongation.
Simultaneous activation in both the endodermis and epidermis resulted in stronger root elongation than activation in either layer alone. The researchers also examined the spatial distribution of enzymes involved in GA biosynthesis. The sites where GA biosynthetic activity was detected did not always coincide with the cell layers in which GA signaling promoted root growth.
In particular, a GA biosynthetic enzyme was detected in the cortex, whereas GA signaling in the epidermis promoted root elongation despite no detectable GA biosynthetic enzyme in this layer. These findings indicate that bioactive GA may move between cells from sites of synthesis to sites where GA signaling promotes growth. The new sGA-mGID1 system provides a way to manipulate plant hormone signaling with both spatial and temporal control.
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