Feedback loop promotes sucrose accumulation in cotyledons to facilitate sugar-ethylene signaling-mediated, etiolated-seedling greening.

De-etiolation is indispensable for seedling survival and development. However, how sugars regulate de-etiolation and how sugars induce ethylene (ET) for seedlings to grow out of soil remain elusive. Here, we reveal how a sucrose (Suc) feedback loop promotes de-etiolation by inducing ET biosynthesis. Under darkness, Suc in germinating seeds preferentially induces 1-amino-cyclopropane-1-carboxylate synthase (ACS7; encoding a key ET biosynthesis enzyme) and associated ET biosynthesis, thereby activating ET core component ETHYLENE-INSENSITIVE3 (EIN3). Activated EIN3 directly inhibits the function of Suc transporter 2 (SUC2; a major Suc transporter) to block Suc export from cotyledons and thereby elevate Suc accumulation of cotyledons to induce ET. Under light, ET-activated EIN3 directly inhibits the function of phytochrome A (phyA; a de-etiolation inhibitor) to promote de-etiolation. We therefore propose that under darkness, the Suc feedback loop (Suc-ACS7-EIN3-|SUC2-Suc) promotes Suc accumulation in cotyledons to guarantee ET biosynthesis, facilitate de-etiolation, and enable seedlings to grow out of soil.

Glucose- and sucrose-signaling modules regulate the Arabidopsis juvenile-to-adult phase transition.

CINV1, converting sucrose into glucose and fructose, is a key entry of carbon into cellular metabolism, and HXK1 functions as a pivotal sensor for glucose. Exogenous sugars trigger the Arabidopsis juvenile-to-adult phase transition via a miR156A/SPL module. However, the endogenous factors that regulate this process remain unclear. In this study, we show that sucrose specifically induced the PAP1 transcription factor directly and positively controls CINV1 activity. Furthermore, we identify a glucose feed-forward loop (sucrose-CINV1-glucose-HXK1-miR156-SPL9-PAP1-CINV1-glucose) that controls CINV1 activity to convert sucrose into glucose signaling to dynamically control the juvenile-to-adult phase transition. Moreover, PAP1 directly binds to the SPL9 promoter, activating SPL9 expression and triggering the sucrose-signaling-mediated juvenile-to-adult phase transition. Therefore, a glucose-signaling feed-forward loop and a sucrose-signaling pathway synergistically regulate the Arabidopsis juvenile-to-adult phase transition. Collectively, we identify a molecular link between the major photosynthate sucrose, the entry point of carbon into cellular metabolism, and the plant juvenile-to-adult phase transition.

Effects of three blood purification methods on serum fibroblast growth factor-23 clearance in patients with hyperphosphatemia undergoing maintenance hemodialysis.

The aim of the present study was to investigate the effects of three blood purification methods on fibroblast growth factor-23 (FGF-23) clearance in patients with hyperphosphatemia undergoing maintenance hemodialysis (MHD). In addition, the correlation between serum FGF-23 and phosphorus (Pi) levels and the clinical implications were identified. Sixty-five MHD patients with hyperphosphatemia were randomly divided into three groups: Hemodialysis, HD (n=23); hemodiafiltration, HDF (n=21); and hemodialysis+hemoperfusion, HD+HP (n=21) groups. Serum Pi, FGF-23, blood urea nitrogen, serum creatinine and associated bio-marker levels were measured prior to and following treatment. The expression level of serum FGF-23 was observed to be positively correlated with Pi (r=0.45, P<0.01). The three blood purification methods that were adopted for the present study exhibited significant and effective clearance of serum Pi (P<0.05). The post-treatment serum FGF-23 levels were significantly decreased in the HDF and HD+HP groups (P<0.05). Therefore, HDF may be an effective method for clearing serum FGF-23 in MHD patients exhibiting hyperphosphatemia.