CO interacts with JAZ repressors and bHLH subgroup IIId factors to negatively regulate jasmonate signaling in Arabidopsis seedlings

Abstract

CONSTANS (CO) is a master flowering-time regulator that integrates photoperiodic and circadian signals in Arabidopsis thaliana. CO is expressed in multiple tissues, including young leaves and seedling roots, but little is known about the roles and underlying mechanisms of CO in mediating physiological responses other than flowering. Here, we show that CO expression is responsive to jasmonate. CO negatively modulated jasmonate-imposed root growth inhibition and anthocyanin accumulation. Seedlings from co mutants were more sensitive to jasmonate, whereas overexpression of CO resulted in plants with reduced sensitivity to jasmonate. Moreover, CO mediated the diurnal gating of several jasmonate-responsive genes under long-day conditions. We demonstrate that CO interacts with JASMONATE ZIM-DOMAIN (JAZ) repressors of jasmonate signaling. Genetic analyses indicated that CO functions in a CORONATINE-INSENSITIVE1 (COI1)-dependent manner to modulate jasmonate responses. Furthermore, CO physically associated with the basic helix-loop-helix (bHLH) subgroup IIId transcription factors bHLH3 and bHLH17. CO acted cooperatively with bHLH17 in suppressing jasmonate signaling, but JAZ proteins interfered with their transcriptional functions and physical interaction. Collectively, our results reveal the crucial regulatory effects of CO on mediating jasmonate responses, and explain the mechanism by which CO works together with JAZ and bHLH subgroup IIId factors to fine-tune jasmonate signaling.

MdbHLH162 connects the gibberellin and jasmonic acid signals to regulate anthocyanin biosynthesis in apple

“…Considering the antagonism of JA and GA in regulating anthocyanin biosynthesis (Figures 1A, B, S1), we continued to explore the effect of MdJAZ1 and MdJAZ2 on the GA-MdRGL2a-MdbHLH162 regulatory pathway. MdJAZ1 and MdJAZ2 favored inhibiting anthocyanin by MdbHLH162 releasing MdbHLH162 from the MdRGL2a-MdbHLH162 complex (Figure 8), which is similar to previous studies on JAZ protein regulatory patterns (Han et al, 2020(Han et al, , 2023An et al, 2021b;Zhang et al, 2023). The JA-MdJAZ1/2-MdbHLH162-MdRGL2a module enables MdbHLH162 to connect the GA and JA signals.…”

The MdNAC72‐MdABI5 module acts as an interface integrating jasmonic acid and gibberellin signals and undergoes ubiquitination‐dependent degradation regulated by MdSINA2 in apple

“…The JAZ proteins have no transcriptional regulation function, but they expand regulatory roles in plant growth and development and coordinate the crosstalk between JA and other plant hormones by interacting with multiple TFs (Santner & Estelle, 2007; Pauwels & Goossens, 2011; Kazan & Manners, 2012). Arabidopsis MYB21/24/30/75, GL1/3, EGL3, TT8, ICE1/2, MYC2/3/4, RHD6, ABI3/5, CO, and ARF10/16 (Fernández‐Calvo et al ., 2011; Qi et al ., 2011; Song et al ., 2011; Hu et al ., 2013; Lv et al ., 2017; Ju et al ., 2019; Han et al ., 2020, 2023; Pan et al ., 2020; Mei et al ., 2023), tomato SlHD8 (Hua et al ., 2021), apple MdMYC2, MdABI4, MdBBX37, MdTRB1, MdVQ10, MdBIM1, and MdbHLH162 (An et al ., 2021a,b,c, 2022, 2023a, 2024; Zhang et al ., 2023) are JAZ interacting proteins. JAZ proteins work by reducing the transcriptional activity of target proteins or disrupting protein–protein interactions.…”

Involvement of CONSTANS-like Proteins in Plant Flowering and Abiotic Stress Response

“…Conversely, AtCO negatively mediates salt tolerance in Arabidopsis by interacting with four ABSCISIC ACID-RESPONSIVE ELEMENT BINDING FACTORS (ABF1, ABF2, ABF3, and ABF4) [150]. Additionally, CO is also a JAZ-binding factor that participates in jasmonic acid signal transduction through protein interactions [151]. OMG1, an uncharacterized Arabidopsis III class COL protein, functions as a regulator of the ROS pathway by modulating the expression of ROS pathway-related genes MYB77 and GRX480 [152].…”