The SMC5/6 complex subunit MMS21 regulates stem cell proliferation in rice

Area of Science:

• Plant Biology
• Molecular Genetics
• Cell Biology

Background:

• The Structural Maintenance of Chromosome (SMC)5/6 complex is vital for DNA metabolism and nucleolar integrity.
• METHYL METHANESULFONATE SENSITIVITY GENE 21 (MMS21), a SUMO E3 ligase within the SMC5/6 complex, is known to be essential for root stem cell maintenance in Arabidopsis.
• The specific function of OsMMS21 in rice development remained largely uncharacterized.

Purpose of the Study:

• To investigate the roles of rice SMC5/6 complex subunits, specifically OsSMC5, OsSMC6, and OsMMS21, in plant cell proliferation.
• To elucidate the molecular mechanisms by which OsMMS21 influences shoot and root development in rice.

Main Methods:

• CRISPR/Cas9 gene editing was employed to generate OsSMC5 and OsSMC6 heterozygous mutants.
• Phenotypic analysis of shoot and root development in wild-type and osmms21 mutants.
• Transcriptome analysis of osmms21 mutants to identify affected gene expression pathways.

Main Results:

• OsSMC5 and OsSMC6 are essential for rice embryogenesis, as homozygous mutants could not be obtained.
• Loss of OsMMS21 function resulted in severe defects in both shoot and root development.
• Transcriptome data revealed downregulation of auxin signaling genes in osmms21 roots and cell cycle-related genes (cycB2-1, MCM) in osmms21 shoots.

Conclusions:

• OsSMC5 and OsSMC6 play indispensable roles during rice embryo development.
• The SUMO E3 ligase OsMMS21 is critical for maintaining stem cell niches in both rice shoots and roots.
• OsMMS21 functions by regulating hormone signaling pathways and cell cycle progression, thereby controlling plant development.