Abstract
The phytohormone jasmonoyl-isoleucine (JA-Ile) regulates fundamental plant processes as developmental and defense responses. JA-Ile mediates the interaction between the F-box protein COI1 (part of the SCFCOI1 E3 ubiquitin ligase) and a JAZ repressor leading to early jasmonate responses. The Arabidopsis JAZ1 protein contains the canonical LPIARR degron sequence, which is responsible for the stabilization of the AtCOI1-JA-Ile-AtJAZ1 complex. In strawberry (Fragaria × ananassa) JAZ family was described at the transcriptional level during fruit development but the information about the interaction mode of this complex is still scarce at the molecular level. To gain insight into the strawberry JA-Ile receptor complex, we evaluated the interaction at the structural level, and protein models were built and analyzed for FaCOI1 and FaJAZ1, FaJAZ8.1, and FaJAZ10. The interaction between FaCOI1 and FaJAZ1, FaJAZ8.1 and FaJAZ10 were explored using several ligands, through molecular docking and molecular dynamics (MD) simulations, finding the strongest interaction with (+)-7-iso-JA-Ile than other ligands. Additionally, we tested interactions between FaCOI1 and FaJAZs by yeast two-hybrid assays in the presence of coronatine (COR, a JA-Ile mimic). We detected strong COR-dependent interactions between FaCOI1 and FaJAZ1. Interestingly, FaJAZ1 contains a new non-canonical (IPMQRK) functional degron sequence, in which Arg and Lys are the key residues for maintaining the interaction of the FaCOI1–COR–FaJAZ1 complex as we observed in mutated versions of the FaJAZ1 degron. Phylogenetic analysis showed that the IPMQRK degron is only present in orthologs belonging to the Rosoideae but not in other Rosaceae subfamilies. Together, this study uncovers a new degron sequence in plants, which could be required to make an alternative and functional JA-Ile perception complex in strawberry.
Highlights
Jasmonates (JAs) are phytohormones that regulate development and stress processes in land plants[1,2,3]
The results indicate that the IPMQRK degron sequence is specific to the Rosoideae subfamily and strawberry JAZ1, which presents the non-canonical degron IPMQRK, is functional in the FaCOI1–COR–FaJAZ1 complex
A. thaliana CORONATINE INSENSITIVE1 (COI1) and TRANSPORT INHIBITOR RESPONSE 1 (TIR1) were clustered in group I, while F. × ananassa COI1 and the other orthologs were grouped in group II, indicating a closer phylogenetic relationship with MdCOI1, VvCOI1, and SlCOI1 (Supplementary Fig. S1b)
Summary
Jasmonates (JAs) are phytohormones that regulate development and stress processes in land plants[1,2,3]. All Arabidopsis JAZ repressors contain a Jas domain involved in the interaction with COI1 and diverse transcription factors such as MYC, EGL, EIN, and MYB among o thers[3]. In Arabidopsis, most JAZ proteins contain at the N-terminal region of the Jas domain, a degron consisting in a canonical sequence LPIAR(R/K) involved in the interaction with COI1 mediated by JA-Ile[1,11,20], some JAZ proteins like JAZ8 lacks this conserved sequence and they are not degraded by 26S p roteasome[20,21]. In silico analysis showed the functional conservation for JA-Ile perception of the IPMQRK degron of FvJAZ128 If this JAZ containing the IPMQRK degron sequence is functional in vivo in cultivated strawberry (Fragaria × ananassa) or if this is distinctive for Fragaria genus or Rosaceae family is still unknown. The results indicate that the IPMQRK degron sequence is specific to the Rosoideae subfamily and strawberry JAZ1, which presents the non-canonical degron IPMQRK, is functional in the FaCOI1–COR–FaJAZ1 complex
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