InterPro domain: IPR030006

Gibberellins are plant hormones that modulate growth and development throughout the whole life cycle of the flowering plant. DELLA proteins are key negative regulators of gibberellin (GA) signaling [ 1 ]. DELLA functions as a transcriptional activator. DELLA lacks a DNA-binding domain, but uses intermediate domain (IDD) proteins to bind DNA. Both coregulators DELLA and SCL3 (scarecrow-like 3) use IDDs as transcriptional scaffolds for DNA binding, antagonistically, and this way they regulate the expression of their downstream targets to control the GA signaling pathway [ 2 , 3 ].

Bioactive GAs promote the interaction between the GA receptor GID1 and DELLA, which leads to rapid degradation of DELLA via the ubiquitin/26S proteasome pathway [ 4 , 5 ]. This way, bioactive GAs promote GA signaling though the degradation of the DELLA repressor.

In Arabidopsis, five DELLA genes have been identified: GAI, RGA, and three RGA-LIKE proteins (RGL1, RGL2, and RGL3) [ 6 ]. Rice and barley each have a single DELLA protein, SLENDER1 (SLR1) [ 7 ] and Slender1 (Sln1) [ 8 ], respectively. DELLA proteins are characterised by a DELLA/TVHYNP motif at the N terminus and a GRAS domain at the C terminus, placing them within the GRAS family of transcriptional regulators [ 9 ].

1. Gibberellin signaling in plants. Development 140, 1147-51
2. DELLA protein functions as a transcriptional activator through the DNA binding of the indeterminate domain family proteins. Proc. Natl. Acad. Sci. U.S.A. 111, 7861-6
3. DELLA and SCL3 balance gibberellin feedback regulation by utilizing INDETERMINATE DOMAIN proteins as transcriptional scaffolds. Plant Signal Behav 9, e29726
4. GA action: turning on de-DELLA repressing signaling. Curr. Opin. Plant Biol. 10, 461-5
5. The molecular mechanism and evolution of the GA-GID1-DELLA signaling module in plants. Curr. Biol. 21, R338-45
6. Genomic analysis of DELLA protein activity. Plant Cell Physiol. 54, 1229-37
7. slender rice, a constitutive gibberellin response mutant, is caused by a null mutation of the SLR1 gene, an ortholog of the height-regulating gene GAI/RGA/RHT/D8. Plant Cell 13, 999-1010
8. Gibberellin-mediated proteasome-dependent degradation of the barley DELLA protein SLN1 repressor. Plant Cell 14, 3191-200