Deciphering the essential role of HOP co-chaperones in auxin signaling

The phytohormone auxin plays an important role in many aspects of plant growth and development, including lateral root formation, embryogenesis, maintenance of apical dominance, shoot and vascular development, or cell elongation and division. In addition, auxin plays a critical role in tplant adaptation responses to environmental cues, such as tropic responses and thermomorphogenesis.

Auxin is perceived in the cells by co-receptors. These co-receptors bind auxin and, through their E3 ligase activity, promote the degradation of auxin-dependent transcriptional repressors, activating, in such a way, the auxin response.

In this study, we uncover that the auxin co-receptor TIR1 is assisted in its folding by the co-chaperones HOPs (HSP70-HSP90 organizing proteins), promoting the stabilization of the auxin co-receptor. In addition, these analyses unravel that the co-chaperones HOP form in vivo complexes with a different co-chaperone, SGT1b, which act cooperatively, along with HSP90, in the folding of TIR1 and the activation of the auxin pathway.

These data highly contribute to understanding auxin signaling regulation in plants. Furthermore, due to the relevance of this phytohormone, this study also provides essential information of important physiological processes involved in plant development and stress response.