RAPTOR Controls Developmental Growth Transitions by Altering the Hormonal and Metabolic Balance.

Area of Science:

• Plant Biology
• Molecular Biology
• Biochemistry

Background:

• Plant growth is regulated by complex signaling networks involving proteins like Target of Rapamycin (TOR).
• Regulatory-Associated Protein of TOR 1B (RAPTOR1B) is a key component of the TOR complex, but its specific role in plants is not fully understood.

Purpose of the Study:

• To investigate the function of RAPTOR1B in Arabidopsis by analyzing the physiological and growth consequences of its mutation.
• To elucidate the impact of disrupted TOR signaling on plant metabolism, development, and hormone interactions.

Main Methods:

• Phenotypic analysis of Arabidopsis mutants.
• Metabolomic, lipidomic, and proteomic profiling.
• Abscisic acid feeding experiments.

Main Results:

• RAPTOR1B mutation severely reduced TOR kinase activity, altering central carbon and nitrogen metabolism, leading to starch accumulation and autophagy induction.
• Mutants exhibited reduced growth, altered cell morphology, decreased CO2 assimilation, and increased stomatal conductance.
• Abscisic acid levels were reduced in mutants, and ABA feeding partially rescued growth defects.

Conclusions:

• RAPTOR1B is essential for regulating plant growth and metabolism via the TOR pathway.
• TOR signaling is intricately linked with abscisic acid synthesis and signaling in Arabidopsis.
• Disruption of RAPTOR1B impacts plant physiology beyond central metabolism, affecting gas exchange and hormone balance.