InterPro domain: IPR005202

Sequence analysis of the products of the GRAS (GAI, RGA, SCR) gene family indicates that they share a variable N terminus and a highly conserved C terminus that contains five recognizable motifs [ 1 ]. Proteins in the GRAS family are major players in gibberellin (GA) signaling, which regulates various aspects of plant growth and development [ 2 ]. Mutation of the SCARECROW (SCR) gene results in a radial pattern defect, loss of a ground tissue layer, in the root. The PAT1 protein is involved in phytochrome A signal transduction [ 2 ].

A sequence, structure and evolutionary analysis showed that the GRAS family emerged in bacteria and belongs to the Rossmann-fold, AdoMET (SAM)-dependent methyltransferase superfamily [ 3 ]. All bacterial, and a subset of plant GRAS proteins, are predicted to be active and function as small-molecule methylases. Several plant GRAS proteins lack one or more AdoMet (SAM)-binding residues while preserving their substrate-binding residues. Although GRAS proteins are implicated to function as transcriptional factors, the above analysis suggests that they instead might either modify or bind small molecules [ 4 ].

Some proteins known to belong to the GRAS family are listed below:
• Arabidopsis thaliana SCARECROW (SCR) protein. It regulates asymetric cell divisions of cortex/endodermal initial cells during root development.
• Arabidopsis thaliana SCARECROW-LIKE (SCL) protein.
• Arabidopsis thaliana GIBBERELLIN-ACID INSENSITIVE (GAI) and REPRESSOR OF GA1 (RGA), two closely related proteins involved in gibberellin signaling.
• Arabidopsis thaliana SHORT ROOT (SHR) protein. It is necessary for cell division and endodermis specification.
• Arabidopsis thaliana PAT1 protein. It inhibits light signaling via the phytochrome A (phyA).
• LATERAL SUPPRESSOR (LS), a protein from tomato that controls the formation of lateral branches during vegetative development.

1. The GRAS gene family in Arabidopsis: sequence characterization and basic expression analysis of the SCARECROW-LIKE genes. Plant J. 18, 111-9
2. PAT1, a new member of the GRAS family, is involved in phytochrome A signal transduction. Genes Dev. 14, 1269-78
3. Bacterial GRAS domain proteins throw new light on gibberellic acid response mechanisms. Bioinformatics 28, 2407-11