Biology – Gene control | e-Consult

DELLA proteins are central to the plant's response to gibberellin (GA) and play a crucial role in regulating plant growth and development. They act as repressors of gene expression, particularly those genes involved in promoting growth.

Repressive Function: In the absence of GA, DELLA proteins accumulate and bind to transcription factors, effectively blocking their ability to activate the expression of genes that promote cell elongation, stem growth, and seed germination. This results in stunted growth and inhibition of these developmental processes.

GA-Induced Degradation: When GA is present, it initiates a signaling cascade that leads to the phosphorylation of DELLA proteins by the GID1 protein. This phosphorylation marks the DELLA proteins for degradation by the ubiquitin-proteasome system. The rate of DELLA protein degradation is directly proportional to the concentration of GA.

Release of Transcription Factors: As DELLA proteins are degraded, the transcription factors they were previously bound to are released. This release allows the transcription factors to bind to DNA and activate the expression of genes involved in cell elongation, stem growth, and seed germination. This leads to the characteristic growth responses to GA.

Overall Outcome: The degradation of DELLA proteins is essential for GA-mediated plant growth. It removes the repression of growth-promoting genes, allowing the plant to exhibit the full range of developmental responses to the hormone. Without GA-induced DELLA degradation, the plant would remain stunted and unable to properly develop.