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Nitrate-dependent anaerobic oxidation of methane (AOM) is a new pathway to reduce methane emissions from paddy ecosystems. The elevated atmospheric CO2 concentration can affect methane emissions from paddy ecosystems, but its impact on the process of nitrate-dependent AOM is poorly known. Based on the automatic CO2 control platform with open top chambers and the 13CH4 stable isotope experiments, the responses of the activity of nitrate-dependent AOM, abundance and community composition of Candidatus Methanoperedens nitroreducens (M. nitroreducens) -like archaea to the gradual increase of CO2 concentration were investigated in paddy fields. We set up two CO2 concentration treatments, including an ambient CO2 and a gradual increase of CO2 (increase of 40 µL ⋅ L-1 per year above ambient CO2 concentration until 160 µL ⋅L-1). The results showed the nitrate-dependent AOM rate of 0.7-11.3 nmol CO2 ⋅ g-1 ⋅ d-1 in the studied paddy fields, and quantitative PCR showed the abundance of M. nitroreducens-like archaeal mcrA genes of 2.2x 106-8.5x 106 copies ⋅ g-1. Compared to the ambient CO2 treatment, the slow elevated CO2 treatment enhanced the nitrate-dependent AOM rate and stimulated the abundance of M. nitroreducens-like archaea, particularly in 5-10 cm soil layer. The gradual increased CO2 concentration treatment did not change the community composition of M. nitroreducens-like archaea, but significantly decreased their diversity. The soil organic carbon content was an important factor influencing the nitrate-dependent AOM process. Overall, our results showed that the gradual increase of CO2 concentration could promote the nitrate-dependent AOM, suggesting its positive role in mitigating methane emissions from paddy ecosystems under future climate change. [ABSTRACT FROM AUTHOR]

SBP-box (Squamosa-promoter binding protein) genes are a type of plant-specific transcription factor and play important roles in plant growth, signal transduction and stress response. However, little is known about the SBP-box genes in pepper (CaSBP), especially in the process of Phytophthora capsici infection. In this study, a novel gene (CaSBP12) was selected from the CaSBP gene family, which was isolated from the pepper genome database in our previous study. The CaSBP12 gene was located in the nucleus of the cell and its silencing in the pepper plant enhanced the defense response against Phytophthora capsici infection. After inoculation with Phytophthora capsici, the root activity of the CaSBP12-silenced plants is compared to control plants, while malondialdehyde (MDA) content is compared viceversa. Additionally, the expression of defense related genes (CaPO1, CaSAR8.2, CaBPR1, and CaDEF1) in the silenced plants were induced to different degrees and the peak of CaSAR8.2 and CaBPR1 were higher than that of CaDEF1. The CaSBP12 over-expressed Nicotiana benthamiana plants were more susceptible to Phytophthora capsici infection with higher EC (electrical conductivity) and MDA contents as compared to the wild-type. The relative expression of defense related genes (NbDEF, NbNPR1, NbPR1a, and NbPR1b) in transgenic and wild-type Nicotiana benthamiana plants were induced, especially the NbPR1a and NbPR1b. In conclusion, these results indicate that CaSBP12 gene negative regulates the defense response against Phytophthora capsici infection which suggests their potentially significant role in plant defense. To our knowledge, this is the first report on CaSBP gene which negative regulate defense response. [ABSTRACT FROM AUTHOR]

Plant aquaporins are responsible for water transmembrane transport, which play an important role on abiotic and biotic stresses. A novel plasma membrane intrinsic protein of CaPIP1-1 was isolated from the pepper P70 according to transcriptome databases of Phytophthora capsici inoculation and chilling stress library. CaPIP1-1 , which is 1155 bp in length with an open reading frame of 861 bp, encoded 286 amino acids. Three introns, exhibited CT/AC splice junctions, were observed in CaPIP1-1 . The numbers and location of introns in CaPIP1-1 were the same as observed in tomato and potato. CaPIP1-1 was abundantly expressed in pepper fruit. Increased transcription levels of CaPIP1-1 were found in the different stresses, including chilling stress, salt stress, mannitol stress, salicylic acid, ABA treatment and Phytophthora capsici infection. The expression of CaPIP1-1 was downregulated by 50 μM HgCl 2 and 100 μM fluridone. The pepper plants silenced CaPIP1-1 in cv. Qiemen showed growth inhibition and decreased tolerance to salt and mannitol stresses using detached leaf method. [ABSTRACT FROM AUTHOR]

Nitrate-dependent anaerobic oxidation of methane (AOM) is a new pathway to reduce methane emissions from paddy ecosystems. The elevated atmospheric CO 2 concentration can affect methane emissions from paddy ecosystems, but its impact on the process of nitrate-dependent AOM is poorly known. Based on the automatic CO 2 control platform with open top chambers and the 13 CH 4 stable isotope experiments, the responses of the activity of nitrate-dependent AOM, abundance and community composition of Candidatus Methanoperedens nitroreducens ( M. nitroreducens )-like archaea to the gradual increase of CO 2 concentration were investigated in paddy fields. We set up two CO 2 concentration treatments, including an ambient CO 2 and a gradual increase of CO 2 (increase of 40 μL·L -1 per year above ambient CO 2 concentration until 160 μL·L -1 ). The results showed the nitrate-dependent AOM rate of 0.7-11.3 nmol CO 2 ·g -1 ·d -1 in the studied paddy fields, and quantitative PCR showed the abundance of M. nitroreducens -like archaeal mcrA genes of 2.2×10 6 -8.5×10 6 copies·g -1 . Compared to the ambient CO 2 treatment, the slow elevated CO 2 treatment enhanced the nitrate-dependent AOM rate and stimulated the abundance of M. nitroreducens -like archaea, particularly in 5-10 cm soil layer. The gradual increased CO 2 concentration treatment did not change the community composition of M. nitroreducens -like archaea, but significantly decreased their diversity. The soil organic carbon content was an important factor influencing the nitrate-dependent AOM process. Overall, our results showed that the gradual increase of CO 2 concentration could promote the nitrate-dependent AOM, suggesting its positive role in mitigating methane emissions from paddy ecosystems under future climate change.

Paddy fields are one of the most important methane sources, which have great impacts on climate change. The nitrite-dependent anaerobic methane oxidation, by NC10 phylum bacteria- Candidatus Methylomirabilis oxyfera ( M. oxyfera )-like bacteria, is a new process regulating methane emission from paddy fields. However, little is known about the spatial and temporal variations of M. oxyfera -like bacterial communities and the regulating factors in paddy soils. We investigated the community composition, diversity, and abundance of M. oxyfera -like bacteria in 0-40 cm depth of paddy soils at key growth stages of rice, including tillering, jointing, flowering, and milky stages. Results of high-throughput sequencing showed that community composition of M. oxyfera -like bacteria differed significantly among different soil layers, while no significant variation was observed among different rice growth stages. The diversity of M. oxyfera -like bacteria increased with soil depth. Real-time quantitative PCR showed that the 16S rRNA gene abundance of M. oxyfera -like bacteria ranged from 5.73×10 6 to 2.56×10 7 copies·g -1 (dry weight), with the highest gene abundance in the 10-20 cm layer. Further, the abundance of these bacteria showed a decreasing trend with rice growth. Soil organic carbon content and soil pH were correlated with the M. oxyfera -like bacterial community structures and abundance. In all, our results suggested a certain degree of heterogeneity of spatial and temporal distribution of M. oxyfera -like bacterial communities in paddy soils, which was largely influenced by soil organic carbon and soil pH.