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The KAI2-SMAX1/SMXL2 Module Regulates Organ Size Through Interaction With Other Hormone Pathways in Arabidopsis
Liangliang Li1, Kun Xu1, Chenbo Zhu1
1Jilin Da'an Agro-Ecosystem National Observation and Research Station, Changchun Jingyuetan Remote Sensing Experiment Station, State Key Laboratory of Black Soils Conservation and Utilization, Northeast Institute of Geography and Agroecology, Chinese Academy of Sciences, Changchun, China.
Physiologia Plantarum
|November 24, 2025
Summary
Karrikin (KAR) signaling, involving KAR INSENSITIVE 2 (KAI2), regulates plant organ size. KAR signaling inhibits growth by restricting cell expansion, impacting hormone pathways and plant development.
Area of Science:
- Plant Biology
- Molecular Plant Physiology
- Hormone Signaling
Background:
- Organ size is a crucial developmental trait regulated by genetic and hormonal factors.
- Karrikins (KARs), smoke-derived compounds, are thought to mimic endogenous hormones regulating plant growth.
- The KAR receptor KAR INSENSITIVE 2 (KAI2) plays a role in KAR signaling.
Purpose of the Study:
- To investigate the role of KAR signaling in regulating plant organ size.
- To elucidate the molecular mechanisms by which KAR signaling affects cell size and hormone pathways.
Main Methods:
- Analysis of KAR signaling mutants (kai2, smax1, smxl2) for organ size phenotypes.
- Microscopic examination of cell size in different plant organs.
- Comparative transcriptome analysis of mutant and wild-type plants.
Main Results:
- KAI2-deficient mutants (kai2) exhibited larger organ sizes, while negative regulator mutants (s1 s2) showed smaller sizes compared to wild-type.
- Cell size investigations revealed that kai2 mutants have larger cells, whereas s1 s2 mutants have smaller cells.
- Transcriptome analyses indicated KAR signaling regulates pathways involving abscisic acid, auxin, cytokinins, and jasmonic acid.
Conclusions:
- KAR signaling acts as an inhibitor of organ size, primarily by restricting cell expansion.
- This regulation involves interactions with multiple hormone signaling pathways and genes controlling organ size determination.
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