Niu, J. | Search bioRxiv

bioRxiv2018

SmbHLH37 functions antagonistically with SmMYC2 in regulating jasmonate-mediated biosynthesis of phenolic acids in Salvia miltiorrhiza

Jasmonates (JAs) are integral to various defense responses and induce biosynthesis of many secondary metabolites. MYC2, a basic helix-loop-helix (bHLH) transcription factor (TF), acts as a transcriptional activator of JA signaling. MYC2 is repressed by the JASMONATE ZIM-domain (JAZ) proteins in the absence of JA, but de-repressed by the protein complex SCFCOI1 on perception of JA. We previously reported that overexpression of SmMYC2 promotes the production of salvianolic acid B (Sal B) in Salvia miltiorrhiza. However, the responsible molecular mechanism is unclear. Here, we showed that SmMYC2 binds to and activates the promoters of its target genes SmTAT1, SmPAL1, and SmCYP98A14 to activate Sal B accumulations. SmbHLH37, a novel bHLH gene significantly up-regulated by constitutive expression of SmMYC2, was isolated from S. miltiorrhiza for detailed functional characterization. SmbHLH37 forms a homodimer and interacts with SmJAZ3/8. Overexpression of SmbHLH37 substantially decreased yields of Sal B. SmbHLH37 binds to the promoters of its target genes SmTAT1 and SmPAL1 and blocks their expression to suppress the pathway for Sal B biosynthesis. These results indicate that SmbHLH37 negatively regulates JA signaling and functions antagonistically with SmMYC2 in regulating Sal B biosynthesis in S. miltiorrhiza.

plant biology↗

bioRxiv2017

Endothelial Cell-Specific MCPIP Deletion Causes Endothelial Dysfunction and Impairs Post-ischemic Angiogenesis in Vivo

Vascular endothelial cells (ECs) play an important role in angiogenesis and inflammatory responses. MCPIP (also known as Zc3h12a or Regnase-1), a newly identified suppressor of cytokine signaling, is expressed in endothelial cells. To directly test the role of endothelium-derived MCPIP in cardiovascular pathophysiology, we specifically targeted deletion of the murine MCPIP gene in the endothelium by using the loxP/Cre system. A floxed MCPIP knock in mouse line was crossbred with VEcadherin5-Cre mice to generate offspring with deletion of the MCPIP gene in ECs (ECKO). Ablation of MCPIP in ECs resulted in systemic inflammation, anemia, splenomegaly, increased vessel permeability, muscle wasting, endothelial dysfunction, thrombus formation, impaired blood perfusion, and reduced lifespan in these mice. Serum levels of cytokines, chemokines, and biomarkers of EC dysfunction were significantly elevated in the ECKO mice, suggesting a hypercytokinemia. These mice also were more susceptible to lipopolysaccharide-induced death. When subjected to ischemia, these mice showed defective post-ischemic angiogenesis and impaired blood flow recovery in hind limb ischemia and stroke models, as well as in wound healing. This effect was associated with an increased cellular infiltration, cytokine expression, and decreased angiogenic factors. Moreover, MCPIP-deficient ECs displayed decreased vascular sprouting and tube elongation in ex vivo aortic ring assay. MCPIP-knockdown in cultured ECs enhanced NF-{kappa}B activity and dysregulated synthesis of microRNAs linked with elevated cytokines and biomarkers of EC dysfunction. These data show, for the first time, that constitutive expression of MCPIP in ECs is essential to maintain ECs in a quiescent state by serving as an important negative feedback regulator that keeps the inflammatory signaling suppressed.

pathology↗