Hypoxia is a common feature of many solid tumours, including cervical cancer. Aggressive tumour progression is mostly associated with hypoxia. Furthermore, hypoxic conditions in tumours are also associated with resistance to chemotherapy and radiation, and with poor prognosis. Hypoxia inducible factor (HIF)-1, composed of a constitutively expressed β-subunit (HIF-β/ARNT) and one of the three known oxygen-regulated α-subunits, HIF-1α, HIF-2α, or HIF-3α, mediates the tumour cell response to hypoxia. The distinction between the roles of HIF-1α and HIF-2α in tumorigenesis is not clearly delineated. Therefore, the aim of the present study was to investigate the effect of HIF-2α on the characteristics of a cervical cancer cell line and to compare the functions of HIF-1α and HIF-2α. The present study demonstrated that the levels of HIF-1α and HIF-2α expression increased under hypoxic exposure compared with normoxia. The major difference was the temporal expression of HIF-1α and HIF-2α, with expression of the two proteins peaking at different time-points. In addition, HIF-1α and HIF-2α had similar effects on proliferation, cell cycle and apoptosis. Suppression of expression of HIF-1α or HIF-2α inhibited proliferation, induced G1-phase arrest and promoted apoptosis in the cervical cancer cell line CaSki. However, the effects of HIF-1α and HIF-2α on invasion and cell autophagy were different. The inhibitory effect of HIF-1α on cell invasion was stronger compared with HIF-2α, while the inhibitory effect of HIF-1α on cell autophagy was weaker compared with HIF-2α. Together, these results demonstrate that HIF-1α and HIF-2α have similar effects on the characteristics of a cervical cancer cell line. The major difference that the authors observed between the effects exerted by the two proteins on the cervical cancer cell line studied is the extent of their effect on invasion and autophagy.

Background: Hypoxia-induced autophagy is a crucial factor that induces chemotherapy resistance in tumor cells. As a key regulator facilitating the adaptation of solid tumors to hypoxia, the role of hypoxia-inducible factors (HIFs) in regulating hypoxia-induced chemotherapy resistance and autophagy has been extensively studied. However, the majority of studies have mainly focused on HIF-1. Direct evidence concerning the role of HIF2A in cisplatin resistance is sparse, and its underlying mechanism is not yet known. Methods: Animal models were constructed by subcutaneously injecting cervical cancer cells stably overexpressing HIF2A (LV-HIF2A) with or without intraperitoneal injection of cisplatin. Tumor size and weight were evaluated to determine tumor growth. Apoptosis was detected by TUNEL assay and protein expression by western blotting. Results: Nude mice injected with cells overexpressing HIF2A showed larger and heavier tumors than those in mice injected with negative control lentivirus (LV-NC)-infected cells, with or without cisplatin. Fewer apoptotic cells were noted in tumor tissues from the LV-HIF2A group than from the LV-NC group, with or without cisplatin. Additionally, expression of the anti-apoptotic protein, B-cell lymphoma 2 (BCL2), and autophagy-related proteins, beclin 1 and autophagy related 5 (ATG5), were found to be higher in the LV-HIF2A group than in the LV-NC group, regardless of cisplatin treatment. Moreover, expression of the pro-apoptotic protein, BCL2-associated X (BAX), was lower in tumor tissues from the LV-HIF2A group than from the LV-NC group. Effect of HIF2A overexpression on cisplatin sensitivity was found to be alleviated in vivo by the autophagy inhibitor, 3-methyladenine (3-MA). Conclusions: HIF2A overexpression promoted tumor growth and autophagy but suppressed apoptosis in vivo, with or without cisplatin. The HIF2A overexpression-affected cisplatin sensitivity was alleviated by 3-MA. Therefore, we suggest that HIF2A overexpression reduces cisplatin sensitivity in cervical cancer by inducing excessive autophagy.

Low-temperature stress (LTS) is a major limiting factor for rice production in high-latitude regions. Many studies have reported the impacts of LTS on leaf photosynthesis and yield, but few of them explored the response of photosynthesis, chloroplast ultrastructure, pollen fertility, cold stress adaptation to LTS at different growth stages of rice. In this study, we conducted a two-year temperature-controlled field experiment (in 2023 and 2024) to investigate the effects of LTS at the tillering, booting, and heading stages on physiological and biochemical characteristics, plant growth, pollen fertility, and grain yield for a japonica rice cultivar (Longgeng31). The results showed that rice photosynthesis gradually decreased as the LTS temperature was decreasing and the LTS duration was increasing. The net photosynthetic rate (P_n) decreased the most at the booting stage, followed by the tillering, and the heading stages. Compared with controlled group (CK), the LTS treatment at 11.5°C for 3–10 days significantly reduced P_n by 52.2% ~ 62.7%, 85.3% ~ 93.9% and 39.3% ~ 44.9%, at the tillering stage, booting and heading stages respectively. Increasing LTS intensity and duration caused distorted chloroplast morphology and reduced plant height. The concentrations of the antioxidant and osmotic regulation systems in rice peaked after 7 days of LTS treatment, indicating that the stress response to LTS showed a trend of initially increasing and subsequently decreasing. The grain yield decreased the most under LTS at the booting stage by 59.30%−88.76% on D10, followed by the heading and tillering stages. After 10 days of exposure to LTS, the pollen viability decreased most significantly at the heading stage by 44.67%, followed by the booting and the tillering stages. These findings could provide a theoretical basis for identifying and evaluating LTS in rice under field conditions, and provide a methodological reference for the identification and monitoring of LTS in other crops, thereby holding significant practical implications.

This study analyzed temperature and yield data from 34 meteorological stations in Heilongjiang Province during 1961–2020. Four climate averages (P₁, P₂, P₃, and P₄) were determined based on their respective time distributions (1961–1990, 1971–2000, 1981–2010, and 1991–2020). The national standard temperature anomaly index was used to identify delayed chilling damage in rice cultivation compared to these climate averages. Climate tendency rate analysis, Mann–Kendall detection, and linear regression methods were employed to examine the relationship between temperature anomaly and rice yield from May to September. The results showed that there were noticeable differences in recognizing delayed chilling damage across different climate averages from 1961 to 2020. The average duration of chilling damage under P₁, P₂, P₃, and P₄ was, respectively, estimated as 8.5 years, 13.3 years, 21.4 years, and 30.9 years, with severe cold damage accounting for a significant portion (68.2–76.0%) of the total chilling damage period. The occurrence of severe cold damage increased significantly over time while light and moderate cold damage did not show a clear increasing or decreasing trend. Based on the test results, P₃ was found to be the most suitable climate average for identifying delayed chilling damage in rice cultivation from 1961 to 2020. Moreover, the incidence of chilling damage revealed declining trend over time. There was a high incidence of chilling damage in the 1960s and 1970s, followed by a decrease from the 1980s to the mid 1990s, and finally a low-incidence period after the mid-1990s. Spatially, the western regions experienced greater occurrence of chilling damage than the eastern regions. Additionally, there was a highly significant positive correlation (p < 0.01) between temperature anomalies from May to September and relative meteorological yield of rice. As temperature anomalies decreased during this period, there was an observed downward trend in relative meteorological yield of rice, indicating that delayed cold injury had a negative impact on rice production.

Rainfall erosivity plays a crucial role in assessing and forecasting soil erosion. Accurate assessment of rainfall erosivity and understanding its spatiotemporal distribution patterns can provide valuable insights for protecting black soil in Northeast China. In this study, we utilized daily rainfall observation data from 142 meteorological stations spanning the years 1961 to 2020 and one-hour precipitation data from 20 stations for 2019 and 2020 in the Black Soil Region in Northeast China (NEBS). We calculated rainfall erosivity using both the classical algorithm and a daily rainfall model, verifying the accuracy of daily rainfall data in calculating erosivity. We then conducted a comprehensive analysis of the spatiotemporal characteristics of rainfall erosivity in NEBS and its constituent provinces and districts, employing trend analysis, wavelet analysis, and IDW (Inverse Distance Weighted) spatial interpolation. Our findings indicate that the semi-monthly model is suitable for calculating rainfall erosivity in NEBS. The correlation coefficients between rainfall erosivity calculated using the classical algorithm and that estimated using the semi-monthly model were 0.9804 and 0.9894 for the years 2019 and 2020, respectively. The intra-annual distribution curves of rainfall erosivity in NEBS and each province or district displayed a single peak, with a prominent peak occurring in the latter half of July. Notably, the total proportion of erosivity generated by rainfall in July and August ranged from 65.4 to 67.7%, underscoring a high degree of concentration. Over the period from 1961 to 2020, the spatial distribution of annual rainfall erosivity (referred to as \({{R}_{a}}\)) in NEBS exhibited a general decreasing trend from south to northwest and northeast. Temporal changes showed an overall non-significant fluctuating upward trend, with \({{R}_{a}}\) at 81.7% of the stations displaying an upward trajectory, and 32.8% of these stations showing a significant increase (P < 0.1). The temporal variation characteristics of each province and region were as follows: \({{R}_{a}}\) showed a significant upward trend (P < 0.05) in Heilongjiang, while the increase and decrease trends in the other three provinces or regions were less pronounced. Notably, the \({{R}_{a}}\) in NEBS and each province or region from 1961 to 2020 exhibited a significant cycle of 3–4 years on a smaller scale.

Agro-meteorological disasters are a significant cause of crop yield reduction. Northeast China is a major base for commodity grain production and is also highly sensitive to climate change. Early frost is one of the most significant meteorological disasters in Northeast China. The typical weather system serves as the primary meteorological cause of the occurrence of early frost. The Northeast Cold Vortex is a cyclonic system of certain intensity located in Northeast China, which has the potential to induce severe weather conditions such as extreme low temperatures and intense convection. Despite extensive research on the first occurrence of frost in Northeast China, the evolutionary characteristics under the combined influence of climate change and the Northeast Cold Vortex remain unclear. This limitation hinders the development of effective monitoring and early warning systems for early frost, as well as the formulation of disaster prevention and mitigation plans for crop production. Therefore, this study aims to objectively document the occurrence of early frost in maize crops in Northeast China from 1961 to 2021 under the influence of the Northeast Cold Vortex. It seeks to unveil the climatic characteristics and evolutionary patterns of early frost events in maize crops within this region, considering the impact of the Northeast Cold Vortex. Additionally, it endeavors to analyze the factors contributing to varying degrees of early frost caused by the Northeast Cold Vortex. The results showed that the occurrence of both early frost and frost influenced by the Northeast Cold Vortex exhibited a declining trend. Furthermore, there was also a decreasing proportion of initial frost attributed to the Northeast Cold Vortex, with a decline rate of 2% per decade, indicating a diminishing dominance of initial frost caused by this weather system. The onset date for the early frost under the influence of the Northeast Cold Vortex progressively advanced from southeast to northwest, occurring 4 days earlier than during the period from 1961 to 1990 between 1991 and 2021. While early frost displayed an increasing spatial distribution from southeast to northwest, it is noteworthy that the majority concentration of the Northeast Cold Vortex was observed in central regions, highlighting its predominant role in causing early frost in Northeast China.