Jasmonate Zim-Domain Protein 9 Interacts With Slender Rice 1 to Mediate the Antagonistic Interaction Between Jasmonic and Gibberellic Acid Signals in Rice

Abstract

The jasmonic acid (JA) and gibberellic acid (GA) signaling pathways interact to coordinate stress responses and developmental processes. This coordination affects plant growth and yield, and is mediated by interactions between the repressors of each pathway, the JASMONATE ZIM-DOMAIN PROTEIN (JAZ) and DELLA proteins. In this study we attempted to identify rice (Oryza sativa) JAZs that interact with rice DELLAs such as SLENDER RICE 1 (SLR1). Analysis of protein–protein interactions showed that OsJAZ8 and OsJAZ9 interact with SLR1; OsJAZ9 also interacted with the SLR1-LIKE (SLRL) protein SLRL2. Based on this broader interaction, we explored the function of OsJAZ9 in JA and GA responses by analyzing transcript levels of the JA-responsive gene OsbHLH148 and the GA-responsive gene OsPIL14 in OsJAZ9-overexpressing (OsJAZ9-Ox) and osjaz9 mutant plants. OsbHLH148 and OsPIL14 encode key transcription factors controlling JA and GA responses, respectively, and JA and GA antagonistically regulate their expression. In OsJAZ9-Ox, the expression of OsbHLH148 was downregulated and the expression of OsPIL14 was upregulated. By contrast, in osjaz9 mutants, the expression of OsbHLH148 was upregulated and the expression of OsPIL14 was downregulated. These observations indicated that OsJAZ9 regulates both JA and GA responses in rice, and this finding was supported by the opposite expression patterns of OsDREB1s, downstream targets of OsbHLH148 and OsPIL14, in the OsJAZ9-Ox and osjaz9 plants. Together, these findings indicate that OsJAZ9 suppresses JA responses and promotes GA responses in rice, and the protein–protein interaction between OsJAZ9 and SLR1 is involved in the antagonistic interplay between JA and GA.

Jasmonic Acid Modulates Xylem Development by Controlling Expression of PIN-FORMED 7

“…For example, JA interacts with gibberellic acid in the coordination of plant development and stress responses. [18][19][20] Based on our results presented here, we propose that JA interacts with auxin and CK to modulate xylem development. Further molecular and genetic studies will enhance our understanding of the molecular mechanisms underlying JA-mediated xylem development and the regulatory interactions between JA and other key phytohormones.…”

Jasmonic Acid Signaling and Molecular Crosstalk with Other Phytohormones

“…By triggering the degradation of DELLAs, GA suppresses ABI5-mediated ABA signaling via stabilized ICE1. Most interestingly, DELLAs [ 131 , 133 ], ICE1 [ 96 ] and ABI5 [ 160 , 161 ] are all targets of JAZ proteins ( Figure 7 ). Therefore, ABI5 appears to be the convergence point where ABA signaling is fine-tuned through the interaction of regulators coming from multiple signaling pathways (such as JA and cold).…”

Crosstalk with Jasmonic Acid Integrates Multiple Responses in Plant Development

“…These studies suggested that the cytokinin response is integral to the JA-dependent stress response and growth modulation. A recent study using overexpression plants and knock-out mutants of OsJAZ9 revealed that OsJAZ9 is a key JAZ protein that mediates the antagonistic interaction of JA and GA [21]. In this study, they identified OsJAZ9 proteins that directly interact with the rice DELLA protein SLENDER RICE 1 (SLR1), and demonstrated that the OsJAZ9-SLR1 interaction mediates the antagonistic interaction of JA and GA in rice by showing that overexpression of OsJAZ9 promotes the GA response while knock-out of OsJAZ9 reduces the GA response.…”

“…However, the nature of the interaction appears to differ depending on the type of cell and tissue. For example, JA and GA antagonistically interact in stem elongation, while they interact synergistically in stamen development [21,104]. JA antagonistically interacts with auxin to modulate apical growth of roots, but synergistically to promote lateral root growth [93,105].…”