Sclerotinia sclerotiorum (Lib.) de Bary is a necrotrophic fungal pathogen which causes disease in a wide range of plants. An observed decrease in photosynthetic performance is the primary reason for the reduction of crop yield induced by S. sclerotiorum. The H2C2O4 is the main pathogenic material secreted by S. sclerotiorum, but the effects of H2C2O4 acidity and the C2O42- ion on photosynthetic performance remain unknown. S. sclerotiorum infection significantly decreased photosynthetic O2 evolution and the maximum quantum yield of photosystem II (Fv/Fm) in tobacco leaves under high-light. H2C2O4 (the main pathogenic material secreted by S. sclerotiorum) with pH 4.0 also significantly decreased photosynthetic performance. However, treatment with H3PO4 and HCl at the same pH as H2C2O4 caused much less decrease in photosynthetic performance than H2C2O4 did. These results verify that the acidity of the H2C2O4 secreted by S. sclerotiorum was only partially responsible for the observed decreases in photosynthesis. Treatment with 40 mM K2C2O4 decreased Fv/Fm by about 70% of the levels observed under 40 mM H2C2O4, which further demonstrates that C2O42- was the primary factor that impaired photosynthetic performance during S. sclerotiorum infection. K2C2O4 treatment did not further decrease photosynthetic performance when D1 protein synthesis was fully inhibited, indicating that C2O42- inhibited PSII by repressing D1 protein synthesis. It was observed that K2C2O4 treatment inhibited the rate of RuBP regeneration and carboxylation efficiency. In the presence of a carbon assimilation inhibitor, K2C2O42 treatment did not further decrease photosynthetic performance, which infers that C2O42- inhibited PSII activity partly by repressing the carbon assimilation. In addition, it was showed that C2O42- treatment inhibited the PSII activity but not the PSI activity. This study demonstrated that the damage to the photosynthetic apparatus induced by S. sclerotiorum is not only caused by the acidity of H2C2O4, but also by C2O42- which plays a much more important role in damaging the photosynthetic apparatus. C2O42- inhibits PSII activity, as well as the rate of RuBP regeneration and carboxylation efficiency, leading to the over production of reactive oxygen species (ROS). By inhibiting the synthesis of D1, ROS may further accelerate PSII photoinhibition.

Background: Merozoite surface protein 1 (MSP1) plays an essential role in erythrocyte invasion by malaria parasites. The C-terminal 19-kDa region of MSP1 has long been considered one of the major candidate antigens for a malaria blood-stage vaccine against Plasmodium falciparum. However, there is limited information on the C-terminal 19-kDa region of Plasmodium ovale MSP1 (PoMSP1₁₉). This study aims to analyze the genetic diversity and immunogenicity of PoMSP1₁₉. Methods: A total of 37 clinical Plasmodium ovale isolates including Plasmodium ovale curtisi and Plasmodium ovale wallikeri imported from Africa into China and collected during the period 2012–2016 were used. Genomic DNA was used to amplify P. ovale curtisi (poc) msp1₁₉ (pocmsp1₁₉) and P. ovale wallikeri (pow) msp1₁₉ (powmsp1₁₉) genes by polymerase chain reaction. The genetic diversity of pomsp1₁₉ was analyzed using the GeneDoc version 6 programs. Recombinant PoMSP1₁₉ (rPoMSP1₁₉)-glutathione S-transferase (GST) proteins were expressed in an Escherichia coli expression system and analyzed by western blot. Immune responses in BALB/c mice immunized with rPoMSP1₁₉-GST were determined using enzyme-linked immunosorbent assay. In addition, antigen-specific T cell responses were assessed by lymphocyte proliferation assays. A total of 49 serum samples from healthy individuals and individuals infected with P. ovale were used for the evaluation of natural immune responses by using protein microarrays. Results: Sequences of pomsp1₁₉ were found to be thoroughly conserved in all the clinical isolates. rPoMSP1₁₉ proteins were efficiently expressed and purified as ~ 37-kDa proteins. High antibody responses in mice immunized with rPoMSP1₁₉-GST were observed. rPoMSP1₁₉-GST induced high avidity indexes, with an average of 92.57% and 85.32% for rPocMSP1₁₉ and rPowMSP1₁₉, respectively. Cross-reactivity between rPocMSP1₁₉ and rPowMSP1₁₉ was observed. Cellular immune responses to rPocMSP1₁₉ (69.51%) and rPowMSP1₁₉ (52.17%) induced in rPocMSP1₁₉- and rPowMSP1₁₉-immunized mice were found in the splenocyte proliferation assays. The sensitivity and specificity of rPoMSP1₁₉-GST proteins for the detection of natural immune responses in patients infected with P. ovale were 89.96% and 75%, respectively. Conclusions: This study revealed highly conserved gene sequences of pomsp1₁₉. In addition, naturally acquired humoral immune responses against rPoMSP1 were observed in P. ovale infections, and high immunogenicity of rPoMSP1₁₉ in mice was also identified. These instructive findings should encourage further testing of PoMSP1₁₉ for rational vaccine design. Graphical

Spring low temperatures are a serious natural threat to wheat production in the Huang-Huai wheat region, and they are often accompanied by weak light environments during the day. To elucidate the response patterns and adaptation mechanisms of winter wheat leaves to low-temperature and weak-light environments, we simultaneously measured prompt chlorophyll a fluorescence, delayed chlorophyll a fluorescence, and modulated 820 nm light reflection; moreover, we analyzed the effects of low temperature and weak light treatment for different duration (2 h and 4 h) on the donor-side activity of photosystem II (PSII), the degree of PSII unit dissociation, the efficiency of light energy absorption and capture by PSII, electron transfer to Q_A⁻ and PSI terminal, PSI activity and cyclic electron transport activity in isolated wheat leaves under controlled conditions. The results, which were corroborated using the three methods, revealed that in low-temperature and weak-light environments, the degree of PSII unit dissociation, and the efficiency of light energy absorption, capture, and electron transfer to Q_A⁻ decreased, while the donor-side activity remained unaffected. In contrast, the efficiency of electron transfer to the PSI terminal and the overall performance of photosynthetic electron transport increased. Comprehensive analysis suggests that the increase in the electron receptor pool at the PSI terminal under low-temperature stress is a crucial factor contributing to the enhanced electron transfer efficiency to the PSI terminal and the improved overall performance of the photosynthetic electron transport chain, which is also a crucial factor in the high cold tolerance of winter wheat.

Nitrogen (N) is a key nutrient influencing wheat growth, grain yield, and quality. A long-term field experiment was conducted using cultivar Zhengmai 1860 to clarify the effects of N topdressing on grain protein composition, starch accumulation, and yield. Treatments included a basal N application of 150 kg ha⁻¹ (N1) combined with four topdressing rates at jointing: 37.5, 75, 112.5, and 150 kg ha⁻¹ (N1 + 37.5, N1 + 75, N1 + 112.5, N1 + 150). Nitrogen topdressing significantly affected the physiological and biochemical characteristics of grains at different spike positions. Amylopectin, globulin, soluble starch (SS), and soluble starch synthase (SSS) accumulated most under 75–112.5 kg ha⁻¹, with N1 + 75 showing the strongest response in basal and middle spike grains. Amylose and granule-bound starch synthase (GBSS) peaked at the middle spike under N1 + 112.5. Protein component (gliadin, glutelin, albumin), amino acids, glutamate synthase (GOGAT), and glutamine synthetase (GS) increased progressively with higher N rates, with maximum accumulation at N1 + 150. Nitrogen topdressing also enhanced spike number (5.05–37.13%), grains per spike (3.86–16.22%), and 1000-grain weight (2.72–5.79%), with the highest yield (9451.7 kg ha⁻¹) at N1 + 112.5. These results highlight the critical role of optimized N management in improving grain composition and yield in wheat.