The GmCYCLOPS paralogs regulate soybean nodulation and exhibit signatures during domestication

Area of Science:

• Plant Biology
• Genetics
• Agronomy

Background:

• Legume-rhizobia symbiosis is crucial for nitrogen fixation in crops like soybean.
• The role of CYCLOPS, a key symbiosis regulator, is not fully understood in cultivated soybean.

Purpose of the Study:

• To identify and characterize soybean CYCLOPS orthologs (GmCYCLOPS1 and GmCYCLOPS2).
• To investigate their function in nodulation and their evolutionary trajectory during soybean domestication.

Main Methods:

• Homology-based sequence analysis identified GmCYCLOPS1 and GmCYCLOPS2.
• Gene expression, subcellular localization, RNA interference, and CRISPR/Cas9 gene editing were used for functional analysis.
• Population genomics analyzed haplotype diversity across wild, landrace, and cultivated soybean accessions.

Main Results:

• GmCYCLOPS1 and GmCYCLOPS2 are nuclear-enriched proteins crucial for nodulation.
• Disrupting or reducing their expression severely impairs nodule formation, while overexpression enhances it.
• GmCYCLOPS1 underwent strong selection during domestication, with a specific haplotype (Hap10) becoming dominant in cultivars.

Conclusions:

• GmCYCLOPS1 and GmCYCLOPS2 are essential regulators of soybean nodulation.
• Divergent selection and geographic differentiation of GmCYCLOPS paralogs, particularly GmCYCLOPS1, occurred during soybean domestication.
• These findings offer valuable genetic resources for improving soybean nodulation traits.