DELLAs Modulate Jasmonate Signaling via Competitive Binding to JAZs

Abstract

Gibberellins (GAs) modulate jasmonate (JA) signaling, which is essential for stress response and development in plants. However, the molecular details of such phytohormone interaction remain largely unknown. Here, we show that the JA ZIM-domain 1 (JAZ1) protein, a key repressor of JA signaling, interacts in vivo with DELLA proteins, repressors of the GA pathway. DELLAs prevent inhibitory JAZ1 interaction with a key transcriptional activator of JA responses, MYC2, and, thus, enhance the ability of MYC2 to regulate its target genes. Conversely, GA triggers degradation of DELLAs, which allows JAZ1 to bind MYC2 and suppress MYC2-dependent JA-signaling outputs. Therefore, our results reveal one means by which GAs suppress cellular competence to respond to JA. Because DELLAs serve as central regulators that mediate the crosstalk of various phytohormones, our model also suggests a candidate mechanism by which JA signaling may be fine-tuned by other signaling pathways through DELLAs.

A bHLH-Type Transcription Factor, ABA-INDUCIBLE BHLH-TYPE TRANSCRIPTION FACTOR/JA-ASSOCIATED MYC2-LIKE1, Acts as a Repressor to Negatively Regulate Jasmonate Signaling inArabidopsis

“…However, new insights have recently emerged on the regulatory mechanisms of JA signaling, including identification of JAZ binding partners, and the influence of circadian rhythms and hormonal crosstalk (Hou et al, 2010;Qi et al, 2011;Song et al, 2011;Goodspeed et al, 2012;Hong et al, 2012;Shin et al, 2012;Yang et al, 2012). These suggest that JA signaling encompasses multiple complicated regulatory mechanisms.…”

“…These data indicate the possibility that JA-activated MYC2 induces expression of early JA-responsive target genes, including JAZs, MYC2, and JAM1, and then de novosynthesized JAM1 negatively regulates the upregulated genes by competition for the same cis-regulatory elements as MYC2. Several JA-biosynthetic enzyme genes are directly regulated by MYC2 and likely to be bound by JAM1 ( Figure 7C) (Hou et al, 2010). Once the high expression of these genes activated by MYC2 begins to be downregulated by JAM1 and JAZ, production of JA and JA-Ile is also downregulated.…”

“…TAT1 and JAZ3 are known to be direct targets of MYC2 and contain putative MYC2 target site(s) within 1000 and 418 bp upstream of the translational start site, respectively ( Figure 8A) (see Supplemental Figures 20D and 20E online) (Chini et al, 2007;Hou et al, 2010). To examine binding of JAM1 to putative MYC2 target sites in the TAT1 and JAZ3 upstream regions, we prepared reporter plasmids in which the LUC reporter was fused with 1000 and 418 bp upstream regions of TAT1 and JAZ3, respectively ( Figure 8A) (see Supplemental Figure 20E online).…”

“…myc2 mutants are defective in JA-mediated root growth inhibition, the expression of JA-responsive genes, and responses to pathogens (Boter et al, 2004;Lorenzo et al, 2004;Chini et al, 2007;Thines et al, 2007). MYC2 directly activates the expression of JAZs and several JA biosynthetic genes (Chini et al, 2007;Thines et al, 2007;Hou et al, 2010). The MYC3 and MYC4 transcription factors are closely related to MYC2 and act additively with MYC2 to regulate different subsets of JA response genes (Cheng et al, 2011;Fernández-Calvo et al, 2011;Niu et al, 2011).…”

SUMO proteases OTS1 and 2 control filament elongation through a DELLA-dependent mechanism

“…Reduced filament elongation is also associated with defects in the Jasmonate (JA) pathway (Stintzi and Browse 2000). GA and JA signalling pathways exhibit different points of interactions through DELLA (Cheng et al 2009;Hou et al 2010;Qi et al 2014). Exogenous applications 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 of JA could rescue the reduced fertility of ots1-1 ots2-1 (Figure 1b).…”