Plant hormone signaling: Is upside down right side up?

Area of Science:

• Plant Biology
• Molecular Plant Physiology
• Developmental Biology

Background:

• Small molecule plant hormones are crucial for development.
• Hormone signaling exhibits pleiotropy, regulating multiple processes.
• Decades of research indicate hormone signaling is canalized through core pathways.

Purpose of the Study:

• To address how a single plant hormone signaling pathway generates diverse developmental outputs.
• To propose a new conceptual framework for understanding plant hormone action.
• To integrate recent findings on hormone-independent regulatory mechanisms.

Main Methods:

• Review and synthesis of existing genetic and molecular studies on plant hormone signaling.
• Analysis of gibberellin and strigolactone signaling pathways as case studies.
• Integration of recent findings on novel regulatory mechanisms.

Main Results:

• Plant hormone signaling, despite pleiotropy, is often viewed as canalized through core pathways.
• The question of how one pathway yields different tissue-specific outputs remains challenging.
• Recent discoveries highlight hormone and core pathway-independent regulation of downstream signaling components.

Conclusions:

• The traditional perspective on plant hormone signaling may be "upside-down".
• Hormone and core pathway-independent mechanisms offer a potential explanation for diverse developmental responses to a single hormone.
• Revisiting the conceptualization of hormone signaling is necessary to fully understand its complexity.