Plant development, a complex orchestration of processes, reaches a crescendo in organogenesis, a key aspect of flowering that unravels fundamental mysteries of plant growth, reproduction, and the pivotal phenomenon of abscission. In a groundbreaking study led by researchers Nobutoshi Yamaguchi and Toshiro Ito from the Nara Institute of Science and Technology in Japan, the intricacies of petal abscission in Arabidopsis thaliana Col-0 have been dissected using advanced proximity ligation assays (PLA) technology.
While abscission, the shedding of plant organs, may seem contrary to conventional development, it plays a pivotal role in plant reproductive success and seed dispersal in angiosperms. The study challenges the notion of abscission as a catastrophic event, revealing it as an actively controlled cellular process dependent on new RNA and protein synthesis, cell-wall collapse, and cytoplasmic and vacuolar reduction.
Notably, the study explores the role of autophagy, an intracellular degradation process, in petal abscission. The research team discovered distinctive changes in vesicle numbers and cytoplasmic components in petal base cells, suggesting the involvement of autophagy. However, understanding the spatiotemporal regulation of these changes remained a challenge.
The study introduces a groundbreaking concept – a phytohormone-mediated chromatin state switch controlling the spatiotemporal-specific activation of autophagy for petal abscission. The gene AGAMOUS, responsible for specifying stamen and carpel identity, and jasmonic acid (JA) were identified as key players in promoting petal abscission. The researchers unraveled a JA-regulated chromatin state switch directing local cell fate determination via autophagy at the base of petals.
During petal maintenance, JA signaling co-repressors inhibit MYC activity, resulting in lower levels of reactive oxygen species (ROS). However, when JA accumulates at petal bases, it triggers chromatin remodeling, enabling MYC factors to promote chromatin accessibility. ANAC102, a downstream target, accumulates before abscission, increasing ROS levels and inducing autophagy.
The induced autophagy at the petal base orchestrates maturation, vacuolar delivery, and breakdown of autophagosomes for terminal cell differentiation. The study extends its insights beyond petal abscission, offering a profound understanding of development, aging, and responses to environmental cues.
Yamaguchi envisions the broader impact of the study, stating, “The insights gained from our study could pave the way for enhanced predictability and manipulation of the timing of petal abscission in ornamental plants. This flexibility and reversibility in controlling the shedding of petals hold promise for advancements in horticulture and agriculture.” The research marks a significant leap towards unraveling the complexities of plant development, offering potential applications in diverse fields.