The physiological and metabolic differences in maize under different nitrogen (N) levels are the basis of reasonable N management, which is vital in improving fertilizer utilization and reducing environmental pollution.  In this paper, on the premise of defining the N fertilizer efficiency and yield under different long-term N fertilization treatments, the corresponding differential metabolites and their metabolic pathways were analyzed by untargeted metabolomics in maize.  N stress, including deficiency and excess, affects the balance of carbon (C) metabolism and N metabolism by regulating C metabolites (sugar alcohols and tricarboxylic acid (TCA) cycle intermediates) and N metabolites (various amino acids and their derivatives).  L-alanine, L-phenylalanine, L-histidine, and L-glutamine decreased under N deficiency, and L-valine, proline, and L-histidine increased under N excess.  In addition to sugar alcohols and the above amino acids in C and N metabolism, differential secondary metabolites, flavonoids (e.g., kaempferol, luteolin, rutin, and diosmetin), and hormones (e.g., indoleacetic acid, trans-zeatin, and jasmonic acid) were initially considered as indicators for N stress diagnosis under this experimental conditions.  This study also indicated that the leaf metabolic levels of N2 (120 kg ha^–1 N) and N3 (180 kg ha^–1 N) were similar, consistent with the differences in their physiological indexes and yields over 12 years.  This study verified the feasibility of reducing N fertilization from 180 kg ha^–1 (locally recommended) to 120 kg ha^–1 at the metabolic level, which provided a mechanistic basis for reducing N fertilization without reducing yield, further improving the N utilization rate and protecting the ecological environment.

Phosphorus (P) is a nonrenewable resource and a critical element for plant growth that plays an important role in improving crop yield.  Excessive P fertilizer application is widespread in agricultural production, which not only wastes phosphate resources but also causes P accumulation and groundwater pollution.  Here, we hypothesized that the apparent P balance of a crop system could be used as an indicator for identifying the critical P input in order to obtain a high yield with high phosphorus use efficiency (PUE).  A 12-year field experiment with P fertilization rates of 0, 45, 90, 135, 180, and 225 kg P₂O₅ ha^–1 was conducted to determine the crop yield, PUE, and soil Olsen-P value response to P balance, and to optimize the P input.  Annual yield stagnation occurred when the P fertilizer application exceeded a certain level, and high yield and PUE levels were achieved with annual P fertilizer application rates of 90–135 kg P₂O₅ ha^–1.  A critical P balance range of 2.15–4.45 kg P ha^–1 was recommended to achieve optimum yield with minimal environmental risk.  The critical P input range estimated from the P balance was 95.7–101 kg P₂O₅ ha^–1, which improved relative yield (>90%) and PUE (90.0–94.9%).  In addition, the P input–output balance helps in assessing future changes in Olsen-P values, which increased by 4.07 mg kg^–1 of P for every 100 kg of P surplus.  Overall, the P balance can be used as a critical indicator for P management in agriculture, providing a robust reference for limiting P excess and developing a more productive, efficient and environmentally friendly P fertilizer management strategy.

Various genetic and biochemical characteristics exist in tea plant cultivars, and they largely determine production suitability and tea quality.  Here, we performed transcriptomic and metabolomic analyses of young shoots of seven tea cultivars and identified major regulatory transcription factors (TFs) for the characteristic metabolites in different cultivars based on weighted gene co-expression network analysis (WGCNA).  Phenotypically, we found that ‘Tieguanyin’ (TGY) and ‘Fujian Shuixian’ (FJSX), which are suitable for oolong tea, had higher catechin contents.  The metabolites of ‘Jinxuan’ (JX) were more prominent, especially the contents of phenolic acids, flavonoids, terpenes, and tannins, which were higher than those of the other six cultivars.  Moreover, ‘Fudingdabai’ (FDDB), which is suitable for white tea, was rich in amino acids, linolenic acid, and saccharides.  At the molecular level, hydroxycinnamoyl CoA quinate hydroxycinnamoyl transferase (HCT) (CsTGY12G0001876, and CsTGY06G0003042) led to the accumulation of chlorogenic acid in TGY.  The main reason for the higher l-ascorbic acid content in FJSX was the high expression levels of L-galactono-1,4-lactone hydrogenase (GalLDH) (CsTGY13G0000389) and Myo-inositol oxygenase (MIOX) (CsTGY14G0001769, and CsTGY14G0001770), which were regulated by WRKY (CsTGY11G0001197).  Furthermore, FDDB, ‘Longjing 43’ (LJ43), ‘Shuchazao’ (SCZ)  and ‘Baihaozao’ (BHZ) had higher free fatty acid contents, among which MYB (CsTGY14G0002344) may be a hub gene for the regulation of palmitoleic acid accumulation.  More importantly, we found that the shoots of TGY were green with purple, mainly due to the accumulation of anthocyanins and the downregulation of the Mg-protoporphyrin IX nonomethyl ester cyclase (MPEC) (CsTGY10G0001989) gene that affects chlorophyll synthesis.  These results will provide a theoretical reference for tea cultivar breeding and suitability.

Huahui 1 is an elite transgenic male sterile restorer line of wild rice abortive-type that expresses a Bacillus thuringiensis (Bt) δ-endotoxin and provides effective and economic control of lepidopteran insects. To exploit Huahui 1 to develop a new Bt rice, the insertion site of the Bt gene was determined by thermal asymmetric interlaced PCR (TAIL-PCR). Bt was located in the promoter region of LOC.Os10g10360, approximately 5.35 Mb from the telomere of the short arm of chromosome 10. For the first time, a Bt cytoplasmic male sterile (CMS) system was developed by introgressing Bt from Huahui 1. The recipient CMS system used consisted of Indonesia paddy rice-type II-32B (maintainer line) and II-32A (male sterile line). Marker-assisted selection was used to increase selection efficiency in the backcrossing program. In BC5F1, the Bt plant 85015-8 was selected for further analyses, as it had the highest SSR marker homozygosity. In addition, the linkage drag of the foreign Bt gene in 85015-8 was minimized to 8.01-11.46 Mb. The foreign Bt gene was then delivered from 85015-8 into II-32A. The resultant Bt II-32A and Bt II-32B lines were both resistant to lepidopteran in field trials, and agronomic traits were not disturbed. The maintainability of II-32B, and the male sterility and general combining ability of II-32A, were not affected by the Bt introgression. This study demonstrates a simple and fast approach to develop Bt hybrid rice.

The sheep genome harbours approximately 20 copies of endogenous beta-retroviruses (enJSRVs), and circumstantial evidence suggests that enJSRVs might play a role in mammalian reproduction, particularly placental morphogenesis. This study was aimed to assess the expression of mRNAs of an enJSRV and its receptor, HYAL2, in the uterus and conceptuses of Mongolian ewes throughout gestation, using real-time reverse transcription polymerase chain reaction and in situ hybridization analysis. The results showed that enJSRV and HYAL2 mRNAs were found to be expressed throughout gestation in the endometrium, chorion, placenta, and conceptus. The enJSRV mRNA was most abundant in the placenta on day 90 of pregnancy, in the endometrium on day 30 and 50, and in the chorion on day 70 and 110. However, HYAL2 mRNA was most abundant in the endometrium on day 30. These differences were all significantly different from each other (P<0.01). In situ hybridization showed that enJSRV and HYAL2 mRNAs were specifically expressed in endometrial luminal epithelium and glandular epithelium, trophoblastic giant binucleated cells (BNCs), endometrial caruncles, placental cotyledons, stroma, trophectoderm, as well as multinucleated syncytia of the placenta and blood vessel endothelial cells. Collectively, little is known about the molecular mechanisms by which trophoblastic differentiation and multinucleated syncytia formation are regulated by enJSRVs. However, the temporal and spatial distributions of enJSRV expression in the uterus and conceptus indicate that differentiation of BNCs and the formation of a multinucleated syncytiotrophoblast involve enJSRV and possibly its cellular receptor, HYAL2. Therefore, enJSRV and HYAL2 appear to play important roles in the female reproductive physiology in this breed of sheep.