PLETHORAs shape Arabidopsis phyllotaxis through modulation of patterning robustness and accelerated inflorescence...

Area of Science:

• Plant biology
• Developmental biology
• Genetics

Background:

• Phyllotaxis, the arrangement of plant organs, typically follows a spiral pattern in Arabidopsis.
• Previous studies showed that mutations in PLETHORA (PLT) genes alter this spiral pattern.
• The underlying mechanisms for these phyllotactic shifts remained unclear.

Purpose of the Study:

• To elucidate the mechanisms behind phyllotactic pattern shifts in Arabidopsis mutants lacking three PLT transcription factors.
• To analyze phyllotaxis in rosettes, inflorescences, and meristems of plt mutants.
• To investigate the roles of auxin and cytokinin networks in PLT-mediated phyllotaxis.

Main Methods:

• Quantitative measurements of phyllotaxis in plt mutants.
• Transcriptomic profiling of plt3 plt7 meristems.
• Genome-wide in vitro binding assays for PLT factors.
• EMS enhancer screening in plt3 plt5 plt7 mutants.

Main Results:

• Primordium positioning in plt3 plt5 plt7 inflorescence meristems showed only subtle increases in noise, linked to disrupted auxin/cytokinin regulation.
• Meristem patterning defects alone did not fully explain deviations in mature mutant inflorescences.
• Accelerated inflorescence development in plt mutants, combined with meristem chirality and stem torsion, caused significant deviations from the spiral pattern.

Conclusions:

• Shoot meristematic PLTs are crucial for robust primordium patterning and phyllotaxis.
• PLTs integrate developmental processes, including accelerated growth, chirality, and torsion, during bolting to maintain phyllotactic stability.
• Understanding PLT function provides insights into plant development and pattern formation.