SLR1

SLR1, or Slender Rice 1, is a gene in Oryza sativa that encodes a DELLA-family transcriptional repressor which antagonizes gibberellin signaling. It is a member of the GRAS transcription factor family, and the protein contains the conserved N-terminal DELLA and TVHYNP motifs required for repression, as well as a C-terminal GRAS domain that mediates protein interactions.

In the gibberellin signaling pathway, the presence of gibberellin allows the GA receptor GID1 to bind GA and interact with SLR1, promoting the recruitment of the SCFSLY1 ubiquitin ligase complex. This leads to ubiquitination and subsequent degradation of SLR1 by the 26S proteasome, lifting repression on GA-responsive genes and enabling growth responses such as stem elongation. When SLR1 accumulates, it suppresses GA-mediated processes, resulting in restrained growth and dwarfism.

Genetically, SLR1 activity modulates plant height and developmental timing in rice by controlling the strength of GA responses. Normal SLR1 function keeps growth in check under low GA conditions, while GA-triggered degradation of SLR1 permits taller growth and other GA-dependent developments. Alterations in SLR1 regulation or stability influence rice stature and development, illustrating the central role of DELLA proteins in cereal GA signaling.

Historically, SLR1 exemplifies the DELLA family of GA signaling repressors that were first characterized in dicots and later in monocots. In rice research, SLR1 has provided a model for understanding how DELLA proteins regulate growth in cereals and has informed breeding strategies aimed at optimizing plant height and yield through manipulation of GA signaling pathways.