The co-chaperone HOP3 plays an essential role in jasmonate hormone signaling and in plant defense

Proteins to be fully functional need to go through a correct folding. In living beings this is achieved in part by proteins called chaperones, which act cooperatively to achieve protein homeostasis. In many cases, these chaperones are assisted by other auxiliary proteins called co-chaperones. Among them we can find the co-chaperone HOP, an acronym for “HSP70-HSP90 organizing protein”, which has been extensively studied in non-plant eukaryotes due to its importance in the folding of important signaling proteins, including the glucocorticoid receptor. In plants, its function has been associated to stress; however it possible function in hormonal networks remains unknown in the plant kingdom.

In this article, researchers from Dr. Mar Castellano's and Dr. Isabel Díaz's groups ,in the frame of a collaborative project of the "Severo Ochoa" programme, show that AtHOP3 has a role in the regulation of hormonal networks in plants, specifically in that of jasmonic acid. HOP3 enhances the correct folding and, therefore, the activity of the jasmonic acid co-receptor COI1, which in the absence of HOP3 turns unsatble. In this way, HOP3 participates in the defense process of plants against necrotrophic fungi, such as gray mold, and herbivorous arthropods, such as the spider mite. Similarly, HOP3 is also involved in the correct root growth inhibition response.

From these data it is concluded that HOP co-chaperones are not only involved in the response to stresses in plants, but also have a broader role in plant biology, which includes the regulation of hormonal networks.