A switch that activates autophagy in Arabidopsis petals

Organogenesis, an important aspect of flowering, helps reveal key processes in plant development such as floral organ formation, attainment of reproductive capacity, and abscission leading to seed and fruit development.

Although abscission, a physiological process involving the shedding of plant organs from the main body of the plant, may seem opposite to the conventional definition of development, it has a significant impact on plant reproductive success and seed dispersal. in angiosperms.

Furthermore, petal abscission depends on new RNA and protein synthesis, as well as cell wall collapse and cytoplasmic and vacuolar reduction, suggesting that rather than being a simple catastrophic event, it is an actively controlled cellular process.

Notably, petal base cells of various plants, such as Japanese morning glory, exhibit distinctive changes in vesicle number and cytoplasmic components, hinting at the role of a process called “autophagy” (a process of intracellular degradation which allows cells to recycle damaged intracellular components). ) in petal abscission. However, how these cellular changes are spatiotemporally regulated and lead to autophagy remains a persistent challenge.

To address this problem, a team of researchers led by Nobutoshi Yamaguchi and Toshiro Ito from the Nara Institute of Science and Technology in Japan used Arabidopsis thaliana Col-0 and mutants/transgenic lines. The study, published in the journal Natural communicationsgoes beyond conventional limits and explores autophagy using advanced proximity ligation assay (PLA) technology.

Researchers used a variety of methodologies and experimental analyzes to study the complex mechanisms governing petal abscission, quantify petal abscission times, and examine the position of flowers when petals shed.

“Our work describes a phytohormone-mediated chromatin state change that controls spatiotemporal-specific activation of autophagy, leading to terminal cell differentiation for petal abscission,” says Yamaguchi.

Researchers found that AGAMOUS, the gene responsible for specifying stamen and carpel identity, and jasmonic acid (JA), promote petal abscission at the base of the petals through cell differentiation. They also identified a JA-regulated chromatin state switch at the base of the petals that directed local cell fate determination via autophagy.

They found that during petal maintenance, co-repressors of JA signaling assemble at the base of the petals to inhibit MYC activity, resulting in lower ROS levels. But when JA accumulates at the base of petals, it triggers chromatin remodeling, allowing MYC factors to promote chromatin accessibility for their downstream targets.

Among these targets, ANAC102 specifically accumulates before abscission to increase ROS levels and induce ATG, thereby triggering autophagy. Autophagy induced at the petal base regulates the maturation, vacuolar delivery, and degradation of autophagosomes for terminal cell differentiation.

In conclusion, the study provides a crucial understanding of the mechanism of petal senescence, highlighting the regulatory role of the JA pathway in orchestrating the maturation and degradation of autophagosomes.

Insights from this study extend beyond the topic of petal abscission and focus on development, aging, and responses to environmental cues. Yamaguchi explains: “Insights from our study could pave the way for improved predictability and manipulation of the timing of petal abscission in ornamental plants. This flexibility and reversibility in controlling petal fall holds promise for advancements in horticulture and agriculture.