Protoplast swelling and hypocotyl growth depend on different auxin signaling pathways ($)

Auxin was the first phytohormone to be discovered and it has been found to have a role in nearly every aspect of plant growth and development. Auxin biology is multi-layered, as you will see in the following summaries. Auxin is regulated at the level of biosynthesis, different receptors, and domain segregation. The known auxin receptors include TIR1 (TRANSPORT INHIBITOR RESPONSE1) and AFB (AUXIN SIGNALING F-BOX) proteins that perceive auxin to induce changes in gene expression. In contrast, ABP1 (AUXIN BINDING PROTEIN1) is involved in rapid physiological response to auxin such as protoplast expansion. ABP1’s role as an auxin receptor is debated in literature; however, in this paper Dahlke et al. present evidence to support ABP1 as a receptor in the rapid non-transcriptional auxin response. Plant Physiol. 10.1104/pp.17.00733