Original paper

Plant Growth Regulation

, Volume 71, Issue 1, pp 77-92

First online:

A novel GRAS protein gene MtSymSCL1 plays a role in regulating nodule number in Medicago truncatula

  • Goon-Bo KimAffiliated withDepartment of Life Science, Sogang University
  • , Young-Woo NamAffiliated withDepartment of Life Science, Sogang University Email author 

Rent the article at a discount

Rent now

* Final gross prices may vary according to local VAT.

Get Access


Legume-rhizobium symbiosis requires the expression of a series of plant genes playing roles in nodulation signaling that leads to the formation of functional nodules. A few plant-specific GRAS proteins have been shown to be involved in early nodulation signaling. Here, we isolated a novel SCARECROW-like GRAS protein gene, MtSymSCL1, from the model legume Medicago truncatula. MtSymSCL1 has unique gene and protein domain structures, and its homologs are identified from various plant species. Phylogenetic analysis showed that MtSymSCL1 could be classified into a novel subclass in the GRAS protein family. MtSymSCL1 transcript accumulated highly in nodulated roots at 14 days after inoculation of Sinorhizobium meliloti. Translationally fused MtSymSCL1-GFP expressed from a viral or the native promoter was co-localized with nuclear localization signal-fused RFP in leaf mesophyll protoplasts, Agrobacterium rhizogenes-transformed hairy root cells, and epidermal cells of nodules that developed on the transformed roots. Unlike SCARECROW of Arabidopsis, however, RNA silencing of MtsymSCL1 did not affect root growth, nor root hair curling and infection thread growth. Nevertheless, MtSymSCL1-silenced roots developed significantly fewer nodules than GUS-silenced roots, as shown by replicated nodulation assay with pot- or agar plate-grown plants. The structure of MtSymSCL1-silenced root nodules appeared similar to that of the wild type, as shown by sectioned nodules stained with green fluorescent dye. Together, these results suggest that MtSymSCL1 plays a role in regulating nodule number during legume-rhizobium symbiosis.


Medicago truncatula Sinorhizobium meliloti MtSymSCL1 GRAS protein RNA silencing Regulation of nodule number