Jasmonate and Phytochrome A Signaling inArabidopsisWound and Shade Responses Are Integrated through JAZ1 Stability  

Abstract

Jasmonate (JA) activates plant defense, promotes pollen maturation, and suppresses plant growth. An emerging theme in JA biology is its involvement in light responses; here, we examine the interdependence of the JA-and light-signaling pathways in Arabidopsis thaliana. We demonstrate that mutants deficient in JA biosynthesis and signaling are deficient in a subset of high irradiance responses in far-red (FR) light. These mutants display exaggerated shade responses to low, but not high, R/FR ratio light, suggesting a role for JA in phytochrome A (phyA) signaling. Additionally, we demonstrate that the FR light-induced expression of transcription factor genes is dependent on CORONATINE INSENSITIVE1 (COI1), a central component of JA signaling, and is suppressed by JA. phyA mutants had reduced JA-regulated growth inhibition and VSP expression and increased content of cis-(+)-12-oxophytodienoic acid, an intermediate in JA biosynthesis. Significantly, COI1-mediated degradation of JASMONATE ZIM DOMAIN1-b-glucuronidase (JAZ1-GUS) in response to mechanical wounding and JA treatment required phyA, and ectopic expression of JAZ1-GUS resulted in exaggerated shade responses. Together, these results indicate that JA and phyA signaling are integrated through degradation of the JAZ1 protein, and both are required for plant responses to light and stress.

Interaction between MYC2 and ETHYLENE INSENSITIVE3 Modulates Antagonism between Jasmonate and Ethylene Signaling inArabidopsis

“…JA enhances anthocyanin accumulation and freezing tolerance (Hu et al, 2013b), inhibits seed germination (Miersch et al, 2008), hypocotyl elongation in the light and the ozone-induced spreading of cell death (Rao et al, 2000;Tuominen et al, 2004), and delays flowering (Robson et al, 2010). Conversely, ET suppresses anthocyanin accumulation (Jeong et al, 2010) and freezing tolerance and enhances seed germination (Linkies et al, 2009;Linkies and Leubner-Metzger, 2012), hypocotyl elongation in the light (Zhong et al, 2012), the ozone-induced spreading of cell death (Overmyer et al, 2000), and flowering (Ogawara et al, 2003).…”

“…Upon perception of JA signal (Fonseca et al, 2009;Yan et al, 2009;Sheard et al, 2010), the F-box protein CORO-NATINE INSENSITIVE1 (COI1) (Xie et al, 1998;Yan et al, 2009) recruits the JASMONATE ZIM-DOMAIN (JAZ) proteins (Chini et al, 2007;Thines et al, 2007;Yan et al, 2007) for degradation, which leads to the release of various downstream factors, including MYC2/JASMONATE INSENSITIVE1 (JIN1), MYC3, and MYC4 (Cheng et al, 2011;Fernández-Calvo et al, 2011;Niu et al, 2011), as well as WD-repeat/bHLH/MYB complex , MYB21, MYB24, and MYB57 (Mandaokar et al, 2006;Song et al, 2011) and the IIId bHLH factors (Nakata et al, 2013;Song et al, 2013b), which regulate diverse JA-mediated functions. These functions include root growth (Dathe et al, 1981;Chen et al, 2011), apical hook formation (Turner et al, 2002), flowering (Robson et al, 2010), stamen development (McConn and Browse, 1996;Song et al, 2011Song et al, , 2013a, leaf senescence (Ueda and Kato, 1980;Shan et al, 2011), secondary metabolism (De Geyter et al, 2012;Schweizer et al, 2013), drought responses (Seo et al, 2011), wounding responses (Mason and Mullet, 1990;Acosta et al, 2013;Mousavi et al, 2013), and defense against pathogen infection Vijayan et al, 1998;Melotto et al, 2006;Rowe et al, 2010;Yang et al, 2012;Zheng et al, 2012) and insect attack (McConn et al, 1997;…”

Plant Immunity: It’s the Hormones Talking, But What Do They Say?

“…Light signaling has been shown to strongly influence hormone-regulated defenses. For instance, Arabidopsis (Arabidopsis thaliana) plants display an altered sensitivity to JA-dependent defenses under conditions of crowding and shade, which is regulated via the photoreceptor phytochrome (Moreno et al, 2009;Robson et al, 2010). This results in a trade-off between resource investment in JA-dependent defense and increased growth to outcompete neighbors (Moreno et al, 2009).…”

Transcriptional Mechanism of Jasmonate Receptor COI1-Mediated Delay of Flowering Time in Arabidopsis

“…Although JA has been implicated in regulating flowering time in several plant species (Krajncic et al, 2006;Robson et al, 2010), the exact role of JA in regulating this important physiological process and the underlying molecular mechanism remains obscure. Here, we report that the COI1-dependent signaling pathway delays flowering of Arabidopsis by repressing the transcriptional expression of FT. We discovered that the APETALA2 (AP2) family TFs TARGET OF EAT1 (TOE1) and TOE2 interact with a subset of JAZ proteins and repress the transcription of FT. Our study uncovers the transcriptional mechanism of JA in regulating flowering time and highlights how the specificity of JA responses is determined.…”