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Self-Activation Loop Maintains Stem Cells for Plant Branching

ATH1-STM heterodimer binds the STM locus to maintain its expression of stem cells for plant branching.

Branching allows plants to occupy space in 3D, an innovation considered essential for their adaption. Stem cells are key to this process because they promote the establishment of new growth axes. But how are these stem cells maintained?

Unlike animals, plants form lateral organs throughout their life from a specialized stem cell-containing tissue – the meristem. In seed plants, branching is achieved by stem-cell-containing axillary meristems, which are initiated from a leaf axil meristematic cell population originally detached from the shoot apical meristem.

Investigators from the Institute of Genetics and Developmental Biology (IGDB) at the Chinese Academy of Sciences (CAS) have uncovered a simple mechanism that is responsible for maintaining the identification of these cells.

“Meristematic cells use a very simple mechanism to keep their identification,” said Professor Jiao Yuling, corresponding author of the paper published in Current Biology. A protein dubbed ATH1 maintains the meristem marker gene SHOOT MERISTEMLESS (STM) expression in the leaf axil to enable meristematic cell fate maintenance.

Specifically, ATH1 protein interacts with STM protein to activate STM transcription and form a self-activation loop. Genetic and biochemical data suggest that ATH1 anchors STM to activate STM as well as other axillary meristem regulatory genes. This auto-regulation allows the STM locus to maintain stem cells for branching.

Although the current study focuses on plants, it may also be applicable to animal research. “Plant cells do not migrate, providing a more tractable system for studying cell lineage and fate determination,” said Jiao. “This research helps us to understand how cell fate can be maintained, and this regulatory circuit may also be utilized by animal stem cells.” [APBN]

Source: Cao, X. et al. (2020). A self-activation loop maintains meristematic cell fate for branching. Current Biology30(10), 1893-1904.