A novel SCARECROW-LIKE3 transcription factor LjGRAS36 in Lotus japonicus regulates the development of arbuscular mycorrhizal symbiosis

The symbiosis with arbuscular mycorrhizal (AM) fungi improves plants' nutrient uptake. During this process, transcription factors have been highlighted to play crucial roles. Members of the GRAS transcription factor gene family have been reported involved in AM symbiosis, but little is known about SCARECROW-LIKE3 (SCL3) genes belonging to this family in Lotus japonicus. In this study, 67 LjGRAS genes were identified from the L. japonicus genome, seven of which were clustered in the SCL3 group. Three of the seven LjGRAS genes expression levels were upregulated by AM fungal inoculation, and our biochemical results showed that the expression of LjGRAS36 was specifically induced by AM colonization. Functional loss of LjGRAS36 in mutant ljgras36 plants exhibited a significantly reduced mycorrhizal colonization rate and arbuscular size. Transcriptome analysis showed a deficiency of LjGRAS36 led to the dysregulation of the gibberellic acid signal pathway associated with AM symbiosis. Together, this study provides important insights for understanding the important potential function of SCL3 genes in regulating AM symbiotic development.

Automated summary

This study identified 67 LjGRAS genes, including seven in the SCL3 group, in Lotus japonicus. The expression levels of three LjGRAS genes were upregulated by arbuscular mycorrhizal (AM) fungal inoculation, with LjGRAS36 specifically induced by AM colonization. Functional loss of LjGRAS36 resulted in a significantly reduced mycorrhizal colonization rate and arbuscular size. Transcriptome analysis revealed that the deficiency of LjGRAS36 dysregulated the gibberellic acid signal pathway associated with AM symbiosis.