Light-induced mobile factors from shoots regulate rhizobium-triggered soybean root nodulation

Area of Science:

• Plant Biology
• Molecular Plant-Microbe Interactions
• Biochemistry

Background:

• Symbiotic nitrogen fixation is crucial for plant nutrition but energetically costly.
• Light availability is a proposed key factor influencing this process.
• Understanding the molecular mechanisms linking light signals to symbiosis is essential.

Purpose of the Study:

• To elucidate the role of light-induced signaling pathways in soybean nodule organogenesis.
• To identify the molecular components integrating light perception with symbiotic signaling.
• To explore how plants coordinate resource allocation for symbiosis based on environmental cues.

Main Methods:

• Investigated light-induced soybean transcription factors GmSTF3/4 and GmFTs.
• Analyzed the interaction between CCaMK, GmSTF3, and GmFT2a.
• Examined the direct activation of nodule-specific genes (NIN, NF-YA1, NF-YB1) by the STF–FT complex.

Main Results:

• Light-induced GmSTF3/4 and GmFTs move from shoots to roots, interdependent in inducing nodule organogenesis.
• Rhizobium-activated CCaMK phosphorylates GmSTF3, initiating GmSTF–GmFT2a complex formation.
• This complex directly upregulates the expression of NIN and NF-Y transcription factors crucial for symbiosis.

Conclusions:

• The CCaMK–STF–FT module acts as a signaling hub, integrating light signals with symbiotic cues.
• This mechanism ensures host plants match symbiotic activity with sufficient carbohydrate supply from photosynthesis.
• Findings offer insights for enhancing plant carbon and nitrogen balance through improved symbiosis.