Shoot and inflorescence branching.

Area of Science:

• Plant developmental biology
• Molecular genetics
• Hormone signaling

Background:

• Postembryonic plant development relies on forming secondary growth axes, including branches and flowers.
• Establishing lateral meristems in leaf axils is the initial step in side-shoot development.
• Key regulators of early lateral meristem development include GRAS, MYB, and bHLH transcription factors.

Purpose of the Study:

• To elucidate the regulatory mechanisms governing lateral bud outgrowth in plants.
• To understand the roles of specific genes and signaling pathways in controlling shoot branching.

Main Methods:

• Investigated the function of MORE AXILLARY GROWTH (MAX) genes in Arabidopsis and RAMOSUS (RMS) genes in pea.
• Examined the influence of the main shoot tip and auxin signaling on lateral bud development.
• Focused on the genetic control of signal production, perception, and transduction inhibiting bud outgrowth.

Main Results:

• Identified MAX and RMS genes as crucial for the production, perception, and transduction of an inhibitory signal for lateral bud outgrowth.
• Demonstrated that the synthesis of this bud outgrowth inhibitor is positively regulated by the main shoot tip via auxin signaling.
• Highlighted the role of HD-ZIP transcription factors (REVOLUTA subfamily) in organizing lateral meristems.

Conclusions:

• Lateral bud outgrowth is tightly regulated by a signaling pathway involving MAX/RMS genes and an unidentified hormone.
• The main shoot tip plays a critical role in controlling branching through auxin-mediated regulation of this inhibitory signal.
• Understanding these pathways is key to manipulating plant architecture and yield.