To comprehensively understand the responses of carbohydrate metabolism and transport to different levels of nitrogen supply in growing shoot tips of crabapple (Malus hupehensis Rehd), enzyme activities and related genes involved in the sugar metabolism pathway were investigated. The nitrogen and chlorophyll content of plants increased with increasing nitrogen supply. High nitrogen application increased the net photosynthesis rate and the growth rate of shoot tips but decreased the synthesis capability of sucrose and sorbitol in mature leaves. However, the shoot tips of plants under high-nitrogen treatment had higher contents of sucrose and sorbitol than did those under low-nitrogen treatment, while the activity of sucrose phosphate synthase and aldose-6-phosphate was increased and the transporters MdSOT and MdSUT were up-regulated. Moreover, the activities of enzymes involved in sucrose and hexose metabolism (including sucrose synthase, fructokinase, and hexokinase) were enhanced in the shoot tips of plants under high-nitrogen conditions, and the expression levels of MdSUSY3 and MdHK1 were significantly up-regulated. These findings indicate that a high nitrogen supply increases the metabolic capacity of assimilatory substances in shoot tips, accelerates the efficiency of sugar utilization and eventually leads to a rapid increase in the growth of shoot tips. Our results highlight that high nitrogen increases the capacity of sugar unloading and metabolic utilization in growing shoot tissues.

BACKGROUND Preimplantation genetic testing (PGT) includes methods that allow embryos to be tested for severe inherited diseases or chromosomal abnormalities. In addition to IVF/ICSI and repeated freezing and thawing of the embryos, PGT requires a biopsy to obtain embryonic genetic material for analysis. However, the potential effects of PGT on obstetric and neonatal outcomes are currently uncertain. OBJECTIVE AND RATIONALE This study aimed to investigate whether pregnancies conceived after PGT were associated with a higher risk of adverse obstetric and neonatal outcomes compared with spontaneously conceived (SC) pregnancies or pregnancies conceived after IVF/ICSI. SEARCH METHODS PubMed, EMBASE, MEDLINE, Web of Science and The Cochrane Library entries from January 1990 to January 2021 were searched. The primary outcomes in this study were low birth weight (LBW) and congenital malformations (CMs), and the secondary outcomes included gestational age, preterm delivery (PTD), very preterm delivery (VPTD), birth weight (BW), very low birth weight (VLBW), neonatal intensive care unit (NICU) admission, hypertensive disorders of pregnancy (HDP), gestational diabetes, placenta previa and preterm premature rupture of membranes (PROM). We further pooled the results of PGT singleton pregnancies. Subgroup analyses included preimplantation genetic diagnosis (PGD), preimplantation genetic screening (PGS), cleavage-stage biopsy combined with fresh embryo transfer (CB-ET) and blastocyst biopsy combined with frozen-thawed embryo transfer (BB-FET). OUTCOMES This meta-analysis included 15 studies involving 3682 babies born from PGT pregnancies, 127 719 babies born from IVF/ICSI pregnancies and 915 222 babies born from SC pregnancies. The relative risk (RR) of LBW was higher in PGT pregnancies compared with SC pregnancies (RR = 3.95, 95% confidence interval [CI]: 2.32–6.72), but the risk of CMs was not different between the two groups. The pooled results for the risks of LBW and CMs were similar in PGT and IVF/ICSI pregnancies. The risks of PTD (RR = 3.12, 95% CI: 2.67–3.64) and HDP (RR = 3.12, 95% CI: 2.18–4.47) were significantly higher in PGT pregnancies compared with SC pregnancies. Lower gestational age (mean difference [MD] = −0.76 weeks, 95% CI −1.17 to −0.34) and BW (MD = −163.80 g, 95% CI: −299.35 to −28.24) were also noted for PGT pregnancies compared with SC pregnancies. Nevertheless, compared with IVF/ICSI pregnancies, the risks of VPTD and VLBW in PGT pregnancies were significantly decreased by 41% and 30%, respectively, although the risk of HDP was still significantly increased by 50% in PGT pregnancies compared with IVF/ICSI pregnancies. The combined results of obstetric and neonatal outcomes of PGT and IVF/ICSI singleton pregnancies were consistent with the overall results. Further subgroup analyses indicated that both PGD and PGS pregnancies were associated with a higher risk of PTD and a lower gestational age compared with SC pregnancies. WIDER IMPLICATIONS This meta-analysis showed that PGT pregnancies may be associated with increased risks of LBW, PTD and HDP compared with SC pregnancies. The overall obstetric and neonatal outcomes of PGT pregnancies are favourable compared with those of IVF/ICSI pregnancies, although PGT pregnancies were associated with a higher risk of HDP. However, because the number of studies that could be included was limited, more randomised controlled trials and prospective cohort studies are needed to confirm these conclusions.

Melatonin has been reported to play roles in regulating carbohydrate levels and plant growth. However, little is known about the exact mechanism by which melatonin regulates sugar levels and growth in plants. In this study, it was found that high levels of melatonin inhibited the growth of wild-type (WT) apple plants and induced significant accumulations of fructose, glucose, and sucrose in apple leaves, while MdFRK2 expression was significantly downregulated. MdFRK2 promoter transiently expressed in tobacco leaves further supported that the expression of MdFRK2 could be inhibited by exogenous melatonin. After applying exogenous melatonin, the suppression of MdFRK2 expression was significantly rescued in transgenic apples overexpressing MdFRK2 via the 35S promoter. Fructose, glucose, and sucrose concentrations increased less as compared to WT apple plants. Wild-type plants showed a stunted phenotype 21 days after melatonin treatment, while MdFRK2 -overexpressing plants exhibited slightly inhibited growth, indicating that the downregulated MdFRK2 expression in response to melatonin was involved in melatonin-mediated growth inhibition. Taken together, these results demonstrate the involvement of MdFRK2 in melatonin-induced sugar accumulation and growth inhibition. Our findings shed light on the roles played by MdFRK2 in connecting melatonin action and plant growth.

annulation of phosphoryl diazomethylarenes and pyridinium 1,4-zwitterionic thiolates generates various trifunctionalized dialkyl 1-phosphoryl-1,9adihydropyrido[2,1-c][1,4]thiazine-3,4-dicarboxylates in good to excellent yields and diastereoselectivities. The annulation involves the nucleophilic attack of thiolates on diazomethylarene-generated carbenes followed by an intramolecular cyclization, is free of catalysts, is atom-economical, and has mild reaction conditions.

No abstract