Induction of gemma (clonal propagule) formation via the activation of GEMMIFER gene. (left) Whole plant image. (right) Magnified view of gemmae forming on the plant surface.
Image Credit: Yuki Hirakawa / Hiroshima University
Scientific Frontline: Extended "At a Glance" Summary: GEMMIFER Gene and Plant Asexual Reproduction
The Core Concept: Researchers have identified the GEMMIFER gene, which acts as a "master switch" to initiate asexual reproduction (cloning) in the model plant Marchantia polymorpha (common liverwort).
Key Distinction/Mechanism: Unlike seed-based reproduction, this process relies on the GEMMIFER gene activating another gene, GCAM1, to trigger the formation of stem cells. These stem cells bypass
Major Frameworks/Components:
- Model Organism: Marchantia polymorpha (common liverwort), utilized because standard model plants like Arabidopsis thaliana do not naturally reproduce this way.
- Gene Editing Tools: The team successfully utilized CRISPR-Cas9 genome editing and artificial microRNA knockdown experiments to suppress the gene, completely halting gemma production.
- Chemical Activation: Transgenic lines allowed researchers to trigger the gene on demand using the drug dexamethasone.
- Preceding Factors: Prior research established that the CLE peptide hormone suppresses this cloning mechanism, which initially pointed the team toward identifying the GEMMIFER gene.
Branch of Science: Molecular Biology, Plant Genetics, and Botany.
Future Application: Understanding this genetic pathway could eventually allow scientists to engineer or induce asexual reproduction in other plants, potentially revolutionizing agricultural propagation, enhancing crop cloning efficiency, and preserving valuable botanical traits without seeds.
Why It Matters: The mechanisms behind plant cloning have historically been a "scientific blind spot" due to the limitations of traditional model organisms. This discovery uncovers the foundational genetic switches governing cellular fate and vegetative reproduction in nature.
A Hiroshima-University-led research team has discovered a key gene responsible for the initiation of gemma development, acting as a "master switch" to start asexual reproduction (cloning) in the model plant Marchantia polymorpha (common liverwort).
Many plants possess the extraordinary ability to bypass seeds and reproduce asexually. This flexibility allows them to regenerate entire bodies from a specialized cell. However, the exact cellular and genetic “switches” behind this process have remained a mystery.
While this capacity is widespread across the plant kingdom, it remains a challenge to study. The primary reason is that standard model organisms, such as Arabidopsis thaliana, do not naturally reproduce in this manner. Consequently, a “scientific blind spot” has emerged, in which the most advanced tools of molecular biology could not be applied to this fascinating phenomenon.
A research team led by Hiroshima University was fortunate to uncover this hidden mechanism by shifting its focus to an emerging model organism, Marchantia polymorpha (common liverwort). Widely found in inhabited areas of the Northern Hemisphere, this plant has a flat, leaf-like body called a thallus and can reproduce by cloning itself through specialized structures known as “gemmae.”
“Marchantia polymorpha is a key to solving the mystery of asexual reproduction in plants,” says Yuki Hirakawa, a professor at Hiroshima University’s Graduate School of Integrated Sciences for Life. “This is because this species spontaneously undergoes asexual reproduction by forming gemmae, and well-established methods for genetic analysis are already available.”
In previous work, the research team found that the CLE peptide hormone suppresses asexual reproduction. Subsequent transcriptome analysis identified a set of genes that changed expression in response to the hormone, leading the team to suspect their involvement in asexual reproduction. In this study, the team conducted CRISPR-Cas9 genome editing and artificial microRNA knockdown experiments to suppress the function of one of these genes. They found that the plant completely ceased gemma production, revealing that this gene, named GEMMIFER, is essential for asexual reproduction.
To further analyze the gene's function, the team created a transgenic line capable of controlling the activity of GEMMIFER via drug administration. When dexamethasone was applied to transiently activate GEMMIFER, it triggered the formation of stem cells, the starting point of gemma development. These newly formed cells continued to grow and successfully developed into mature gemmae. This confirmed that the activation of this single gene is sufficient to set the entire cloning process in motion.
Further analysis revealed that GEMMIFER functions by activating the gene GCAM1, which previous studies have shown is also required for gemma formation. This interaction provides key insights into the early stages of the genetic pathway that triggers the stem cell identity of gemmae.
“The precise way this gene reprograms cell fate is still not fully understood. Furthermore, while many plants possess similar genes, it remains to be seen whether they share the same functional role,” Hirakawa notes.
“However,” he adds, “the fact that we could not observe this in traditional model plants does not mean it isn't happening elsewhere in nature. This discovery reminds us of the vast biological secrets still waiting to be uncovered.”
Funding: This work was supported by JSPS KAKENHI (JP22H02676); the Takeda Science Foundation; the Foundation of Kinoshita Memorial Enterprise; the Naito Foundation; the Sumitomo Foundation; the Japan Science and Technology Agency (JST) GteX Program Japan (JPMJGX23B0); the Program for Forming Japan’s Peak Research Universities (J-PEAKS) from JSPS; the Biotechnology and Biological Sciences Research Council (BBSRC), UK Research and Innovation (BB/T007117/1, BB/F011458/1); a Leverhulme Early Career Fellowship (ECF-2023-534); the Leverhulme Trust and the Isaac Newton Trust (23.08[f]); and the Herschel Smith Fund studentship.
Published in journal: Current Biology
Title: Initiation of asexual reproduction by the AP2/ERF gene GEMMIFER in Marchantia polymorpha
Authors: Go Takahashi, Saori Yamaya, Facundo Romani, Ignacy Bonter, Kimitsune Ishizaki, Masaki Shimamura, Tomohiro Kiyosue, Jim Haseloff, and Yuki Hirakawa
Source/Credit: Hiroshima University
Reference Number: mbio050426_02
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