[Effect of seasonal distribution in precipitation on soil nitrogen mineralization in a subtropical forest]. / é™æ°´å­£èŠ‚æ€§åˆ†é å¯¹äºšçƒ­å¸¦æ£®æž—åœŸå£¤æ°®çŸ¿åŒ–çš„å½±å“.

Soil N mineralization is a key process of nutrient cycling in ecosystems. The mechanism of the seasonal distribution of precipitation on soil N mineralization remains unclear. We conducted a precipitation manipulation experiment in a subtropical forest in the middle and lower reaches of the Yangtze River in China from 2020 to 2022, with three treatments, including control (CK), decreased precipitation in the dry season with extremely increased precipitation in the wet season (T1), and decreased precipitation in the dry season with proportionally increased precipitation in the wet season (T2). With in situ resin core method, we explored the effect of seasonal distribution of precipitation on soil N mineralization. The results showed that T1 and T2 significantly decreased dry season net nitrification rate by 57.9% and 72.5% and the net N mineralization rate by 82.5% and 89.6%, respectively, and significantly increased wet season net nitrification rate by 64.3% and 79.5% and net N mineralization rate by 64.2% and 81.1%, respectively. Proportionally increased precipitation in the wet season was more conducive to soil N mine-ralization process than extremely increased precipitation in the wet season. Results of the structural equation model showed that change in seasonal distribution of precipitation could significantly affect soil N mineralization processes in the subtropical forest by changing soil water content, ammonium nitrogen, microbial biomass nitrogen, and soil C:N. Our results had important reference for understanding soil nitrogen cycling and other ecological processes, and were conducive to more accurate assessment on the impacts of future changes in seasonal precipitation pattern on subtropical forest ecosystems.

Germline FOXJ2 overexpression causes male infertility via aberrant autophagy activation by LAMP2A upregulation.

Spermatogenesis is a complex biological process that produces haploid spermatozoa and requires precise regulation by many tissue-specific factors. In this study, we explored the role and mechanism of Fork head box J2 (FOXJ2, which is highly expressed in spermatocytes) in the regulation of spermatogenesis using a germline-specific conditional Foxj2 knock-in mouse model (Stra8-Cre; Foxj2 tg/tg mouse). Foxj2 overexpression in mouse testes led to spermatogenesis failure, which started at the initiation of meiosis, and resulted in male infertility. Lysosomes and autophagy-related genes were upregulated in Stra8-cre; Foxj2 tg/tg mouse testes and the number of autolysosomes in the spermatocytes in Stra8-cre; Foxj2 tg/tg mice was increased. Chromatin immunoprecipitation-PCR and Dual-luciferase reporter assays showed that Lamp2 (encoding lysosome-associated membrane protein-2) was a target of FOXJ2. Foxj2 overexpression increased the expression levels of Lamp2a and Hsc70 (70-kDa cytoplasmic heat shock protein) in the Stra8-cre; Foxj2 tg/tg mouse testes. Our results suggested that Foxj2 overexpression in the germ cells of mouse testes affects chaperone-mediated autophagy by upregulating LAMP2A, leading to spermatogenesis failure at the initiation of meiosis, thus resulting in male infertility. Our findings provide a new insight into the function of FOXJ2 in spermatogenesis and the significance of autophagy regulation in spermatogenesis.

[Impact of overexpressed FOXJ2 on mouse spermatogenesis and its action mechanism].

OBJECTIVE: To analyze the phenotype of the male reproductive system in the germline-specific conditional Foxj2 knock-in mouse model (Stra8-cre; Foxj2tg/+), identify a target gene of the transcription factor FOXJ2, and investigate the effect of the overexpression of Foxj2 on mouse spermatogenesis and its action mechanism. METHODS: Based on the Cre-loxP recombination system, we generated a germline-specific conditional Foxj2 knock-in mouse model (Stra8-cre; Foxj2tg/+). We determined male fertility by counting the number of pups per litter and the fertilization rate after intracytoplasmic sperm injection (ICSI), observed the morphology of the testes and epididymides by HE staining, examined the sperm quality by computer assisted sperm analysis (CASA), detected the expression and localization of Cx43 in the testis by RT-qPCR, Western blot and immunohistochemistry, and verified the binding site of FOXJ2 to the Cx43 promoter using ChIP-PCR and dual luciferase reporter assay. RESULTS: The number of pups per litter and fertilization rate after ICSI were lower in the Stra8-cre; Foxj2tg/+ male mice than in the controls, and so were the size and weight of the testis. HE staining exhibited obvious exfoliation of germ cells and dramatically decreased spermatocytes and spermatids in the seminiferous tubules of the Stra8-cre; Foxj2tg/+ mice. Moreover, sperm concentration in the cauda epididymides was reduced, and the transcription and expression levels of Cx43 in the testis were increased. ChIP-PCR and dual luciferase reporter assay showed direct binding of FOXJ2 to the Cx43 promoter in the testis. CONCLUSIONS: Overexpressed FOXJ2 may lead to spermatogenic failure and subfertility in Stra8-cre; Foxj2tg/+ male mice by upregulating the expression of Cx43.

[Influence of snow depth changes on leaf litter decomposition of Fraxinus mandshurica and Larix gmelinii]. / æ¨¡æ‹Ÿé›ªè¢«å˜åŒ–å¯¹æ°´æ›²æŸ³å’Œå ´å®‰è½å¶æ¾å‡‹è½å¶åˆ†è§£çš„å½±å“.

Changes in snowpack induced by climate change can profoundly affect forest litter decomposition. A snow depth manipulation experiment with three treatments (i.e.,control,snow addition, and snow removal) was conducted to assess the effects of snow depth changes on leaf litter decomposition of two temperate tree species [Manchurian ash (Fraxinus mandshurica) and Dahurian larch (Larix gmelinii)]. The annual loss of the litter mass after one year decomposition varied between 51.3% and 57.4% for the ash and between 21.7% and 31.4% for the larch. The decomposition constants (k) ranged from 0.048 to 0.057 and from 0.022 to 0.030 for these two species respectively.The greatest k value occurred under the snow addition treatment, while the least occurred under the snow removal treatment.Snow addition treatment shortened the 50% and 95% decomposition time by 1.1 months and 4.2 months for the ash, respectively, and by 3.7 months and 15.5 months for the larch, respectively. The snow removal treatment lengthened those decomposition time by 1.8 months and 6.4 months for the ash,and by 5.0 months and 21.1 months for the larch, respectively. Litter decomposition rate was significantly correlated with tree species, snow depth, decomposition time, and soil temperature, but its major influencing factors varied with decomposition stage. Soil temperature and the initial litter quality were the major factors affecting decomposition rates during the snow covered and following snow free periods, respectively. Our findings highlight that changes in snow depth exert significantly instantaneous and prolonged effects on forest litter decomposition.

[Effects of changes in seasonal snow-cover on litter decomposition and soil nitrogen dynamics in forests.] / 季节性雪被变化对森林凋落物分解及土壤氮动态的影响.

Changes in snow-cover patterns induced by global climate change profoundly influence ecological processes in terrestrial ecosystems, including litter decomposition and soil nutrient cycling. Forest, a major terrestrial ecosystem, plays a crucial role in global biogeochemical cycling. Here, we reviewed the effects of changes in seasonal snow-cover on litter decomposition and soil nitrogen (N) cycling in forests. Global climate change would result in increasing or decreasing seasonal snow-cover depending on local conditions, with direct and indirect effects on forest litter decomposition. The changes in seasonal snow-cover would directly affect decomposition process by changing environmental temperature and moisture, litter quality, and decomposer dynamics, and would indirectly influence decomposition via altering community structure, vegetation phenology, and soil nutrients. Meanwhile, the changes in seasonal snow-cover would modify forest soil N dynamics through changing N enrichment, soil temperature and moisture, freeze-thaw cycle, forest community, subnivean fauna and microorganisms. Further studies in this field should focus on: 1) employing experiments with divergent protocols to simulate diverse changing patterns of seasonal snow-cover under the global climate change scenarios; 2) the effects of the seasonal snowmelt leaching on forest litter decomposition and soil N dynamics; 3) elucidating mechanisms underlying forest litter decomposition and soil N dynamics driven by changes in seasonal snow-cover patterns in different ecosystems and climate zones; and 4) quantifying the instantaneous and prolonged effects of changes in seasonal snow-cover on forest litter decomposition and soil N dynamics in the snow-covered and snow-free seasons, respectively. These studies will provide theoretical basis and solid data support for the understanding and model-prediction of the responses of the biogeochemical cycle in terrestrial ecosystems to global climate change.