The chromosome-level holly (Ilex latifolia) genome reveals key enzymes in triterpenoid saponin biosynthesis and fruit color change.

The Ilex L. (hollies) genus of Aquifoliaceae shows high species diversity in tropical and subtropical regions of Asia and South America. Throughout the range of the genus, Ilex species have been widely used in beverage and medicine production and as ornamentals. Here, we assembled a high-quality, chromosome-level genome of Ilex latifolia, which has extremely high economic value because of its useful secondary metabolite production and the high ornamental value of its decorative red berries. The 99.8% genome sequence was anchored to 20 pseudochromosomes, with a total length of 766.02 Mb and a scaffold N50 of 33.45 Mb. Based on the comparative genomic analysis of 14 angiosperm species, we recovered I. latifolia as the sister group to all other campanulids. Two whole-genome duplication (WGD) events were identified in hollies: one shared ancient WGD in the ancestor of all eudicots and a recent and independent WGD in hollies. We performed a genome-wide search to screen candidate genes involved in the biosynthesis of pentacyclic triterpenoid saponins in I. latifolia. Three subfamilies of CYP450 (CYP71A, CYP72A, and CYP716A) appear to have expanded. The transcriptomic analysis of I. latifolia leaves at five developmental stages revealed that two CYP716A genes and one CYP72A gene probably play important roles in this biosynthetic pathway. In addition, we totally identified 12 genes in the biosynthesis pathways of pelargonidin and cyanidin and observed their differential expression in green and red fruit pericarps, suggesting an association between pelargonidin and cyanidin biosynthesis and fruit pericarp color change. The accumulation of pelargonidin and cyanidin is expected to play an important role in the ornamental value of I. latifolia. Altogether, this study elucidated the molecular basis of the medicinal and ornamental value of I. latifolia, providing a data basis and promising clues for further applications.

Complete plastome sequence of Hoya carnosa (L. f.) R. Br. (Apocynaceae).

Hoya is a remarkable genus with high horticultural ornamental value. In this study, we report and characterize the complete plastid genome sequence of Hoya carnosa. The complete chloroplast genome was 176,340 bp in length, which includes a pair of inverted repeat regions (IRs) of 41,381 bp separated by a large single copy region (LSC) 91,281 bp and a small single copy region (SSC) 2,297 bp. Interestingly, IRs expanded into SSC, with the result that most of the genes in SSC were duplicated. This chloroplast genome contained 110 genes, including 76 protein-coding genes, 30 tRNA genes, and 4 rRNA genes. The complete plastome sequence of H. carnosa will provide some useful information for future phylogenetic study of Hoya and its horticultural application.

The complete chloroplast genome of the highly poisonous plant Cerbera manghas L. (Apocynaceae).

The complete chloroplast genome of Cerber amanghas L., a species of the tribe Plumerieae of the family Apocynaceae, is determined for the first time here. The chloroplast genome is 154,428 bp long, containing a large single-copy region (LSC) of 85,138 bp and a small single-copy region (SSC) of 17,390 bp, which are separated by a pair of 25,950 bp long inverted repeat regions (IRs). It encodes a total of 115 genes, including 81 unique protein-coding genes, 30 unique tRNA genes, and 4 unique rRNA genes.Phylogenetic analysis revealed that C.manghas is a member of the paraphyletic tribe Plumerieae of Apocynaceae and is closely related to Thevetia peruviana.

[Nitrite Type Denitrifying Phosphorus Removal Capacity of Cycle Activated Sludge Technology Processes Under Different Inducing Patterns].

A modified cyclic activated sludge technology (CAST) reactor was utilized to investigate the phosphorus and nitrogen removal performance under different inducing patterns in this experiment. The results show that nitrite addition under anoxic conditions has a more inhibitory effect on the denitrifying phosphorus removal performance of the sludge. The phosphorus removal performance of the system was least effective when nitrite dosage was 5 mg·L-1. Compared to an anoxic addition system, the CAST system is more stable under aerobic addition conditions. The phosphorus removal properties have a slight fluctuation during each initial operating condition when the nitrite concentrations are 5, 10 and 15 mg·L-1, respectively. However, the phosphorus removal rate was observed to recover quickly and remain stable at more than 95% after acclimatizing for 10, 6, and 34 days, respectively. The effluent phosphorus concentration was less than 0.5 mg·L-1 in all cases. It was also found that the phosphorus removal performance deteriorated drastically when the nitrite dosage was 20 mg·L-1. Nevertheless, the nitrite type denitrifying phosphorus uptake capacity of the sludge was 10.4 times greater than that of the sludge before acclimatizing, suggesting that the phosphorus performance deterioration due to nitrite addition could be relieved and long-term addition is beneficial to enriching denitrifying phosphorus accumulating bacteria using NO2- as an electron acceptor. Moreover, the sludge settling performance was found to be effective and the sludge concentration decreased continuously when adding a certain concentration of nitrite under aerobic conditions, which is of significant for sludge reduction.

[Synergetic Inhibitory Effect of Free Ammonia and Aeration Phase Length Control on the Activity of Nitrifying Bacteria].

Three sequencing batch reactors (SBRs) labeled with R(Ahead), R(Exact) and R(Exceed) were employed to investigate the synergetic inhibition effect of free ammonia (FA) and length of aeration phase on the activity of ammonia-oxidizing bacteria ( AOB) and nitrite- oxidizing bacteria (NOB) after shortcut nitritation was achieved in the systems. The experiments were conducted under the conditions of three FA concentrations (0.5, 5. 1, 10.1 mg · L⁻¹) combined with three kinds of aeration time (t(Exact): the time when ammonia oxidation was completed; t(Ahead): 30 min ahead of the time when ammonia oxidation was completed; t(Exceed): 30 min exceeded when the time ammonia oxidation was completed). It was found that short-cut nitrification could be successfully established in three reactors with a FA level of 10.1 mg · L⁻¹. Meanwhile, the speed of achieving nitritation was in the sequence of R(Ahead) > R(Exact) > R(Exceed) with operational cycles of 56, 62 and 72, respectively. Compared to AOB, NOB in the three reactors was observed to be more sensitive to FA, resulting in AOB activity higher than NOB activity throughout the whole experimental period. Moreover, there was great difference in the activity coefficient ( η) between AOB and NOB. The activity coefficients of AOB were in the order of η(RExact) > η(RExceed) > η(RAhead) with the values of 104.4%, 100% and 85.8%, respectively. Nevertheless, the activity coefficients of NOB were in the order of η(RExceed) > η(RExact) > η(RAhead) with the values of 71.2%, 64.9% and 50.2%, respectively.

[Startup, stable operation and process failure of EBPR system under the low temperature and low dissolved oxygen condition].

A sequencing batch reactor (SBR) was started up and operated with alternating anaerobic/oxic (An/O) to perform enhanced biological phosphorus removal (EBPR) under the condition of 13-16 degrees C. The results showed that under the condition of low temperature, the EBPR system was successfully started up in a short time (<6 d). The reactor achieved a high and stable phosphorus removal performance with an influent phosphate concentration of 20 mg x L(-1) and the dissolved oxygen (DO) concentration of 2 mg x L(-1). The effluent phosphate concentration was lower than 0.5 mg x L(-1). It was found that decreasing DO had an influence on the steady operation of EBPR system. As DO concentration of aerobic phase decreased from 2 mg x L(-1) to 1 mg x L(-1), the system could still perform EBPR and the phosphorus removal efficiency was greater than 97.4%. However, the amount of phosphate released during anaerobic phase was observed to decrease slightly compared with that of 2 mg x L(-1) DO condition. Moreover, the phosphorus removal performance of the system deteriorated immediately and the effluent phosphate concentration couldn't meet the national integrated wastewater discharge standard when DO concentration was further lowered to 0.5 mg x L(-1). The experiments of increasing DO to recover phosphorus removal performance of the EBPR suggested the process failure resulted from low DO was not reversible in the short-term. It was also found that the batch tests of anoxic phosphorus uptake using nitrite and nitrate as electron acceptors had an impact on the stable operation of EBPR system, whereas the resulting negative influence could be recovered within 6 cycles. In addition, the mixed liquid suspended solids (MLSS) of the EBPR system remained stable and the sludge volume index (SVI) decreased to a certain extend in a long run, implying long-term low temperature and low DO condition favored the sludge sedimentation.