Labile organic carbon (LOC) fractions and related enzyme activities in soils are considered to be early and sensitive indicators of soil quality changes. We investigated the influences of fertilization and residue incorporation on LOC fractions, enzyme activities, and the carbon pool management index (CPMI) in a 10-year field experiment. The experiment was composed of three treatments: (1) no fertilization (control), (2) chemical fertilizer application alone (F), and (3) chemical fertilizer application combined with incorporation of wheat straw residues (F + R). Generally, the F + R treatment led to the highest concentrations of the LOC fractions. Compared to the control treatment, the F + R treatment markedly enhanced potential activities of cellulase (CL), β-glucosidase (BG), lignin peroxidase (LiP), and manganese peroxidase (MnP), but decreased laccase (LA) potential activity. Partial least squares regression analysis suggested that BG and MnP activities had a positive impact on the light-fraction organic carbon (LFOC), permanganate-oxidizable carbon (POXC), and dissolved organic carbon (DOC) fractions, whereas laccase activity had a negative correlation with those fractions. In addition, the F + R treatment significantly increased the CPMI compared to the F and control treatments. These results indicated that combining fertilization with crop residues stimulates production of LOC and could be a useful approach for maintaining sustainable production capacity in lime concretion black soils along the Huai River region of China.

No abstract

The use of alkaline solutions, especially 0.1 to 0.5 M NaOH solutions, for the extraction of humic substances (HS) from soils is controversial because of the potential for chemical and physical alteration of the organic materials in soils. Therefore, it is important to investigate the effects of NaOH extraction on the chemical structure of natural organic matter (NOM) in terrestrial ecosystems. By using solid-state nuclear magnetic resonance, we investigated the impact of NaOH and water extractions on the chemical structure of insoluble and extractable fractions of three model components of NOM: cellulose, van Soest lignin, and peat. We found both sp 2 -hybridized and carboxyl C groups occurred in the NaOH-extractable cellulose fraction relative to the bulk cellulose. Compounds solubilized from the lignin by treatment with 0.1 M NaOH were dominated by aromatic C-O, aromatic C, and OCH 3 functional groups, indicating that some free phenolic monomers were extracted by the alkaline solution. Compared with the bulk peat, the concentration of COO/NCO and sp 2 -hybridized C in NaOH-reconstituted peat sample increased by 40 and 5%, respectively, whereas the concentration of carbohydrate C decreased by 14%. In summary, the chemical structures of cellulose, van Soest lignin, and the peat were altered to some extent by the 0.1 M NaOH extraction. These observations provide useful context in the consideration of potential alterations in chemical composition when one interprets results of HS extractions employing NaOH solutions. Future research will establish the proportion of these alterations that may result from an alternative, slower procedure for acidifying solutions after NaOH extraction.

Simultaneous targeting multiple genes is a big advantage of CRISPR (clustered regularly interspaced short palindromic repeats) genome editing but challenging to achieve in CRISPR screening. The crosstalk among genes or gene products is a common and fundamental mechanism to ensure cellular stability and functional diversity. However, the screening approach to map high-order gene combinations to the interesting phenotype is still lacking. Here, we developed a universal in-library ligation strategy and applied it to generate multiplexed CRISPR library, which could perturb four pre-designed targets in a cell. We conducted in vivo CRISPR screening for potential guide RNA (gRNA) combinations inducing anti-tumor immune responses. Simultaneously disturbing a combination of three checkpoints in CD8+ T cells was demonstrated to be more effective than disturbing Pdcd1 only for T cell activation in the tumor environment. This study developed a novel in-library ligation strategy to facilitate the multiplexed CRISPR screening, which could extend our ability to explore the combinatorial outcomes from coordinated gene behaviors.

No abstract