ABSTRACT
Improving the soil structure and fertility of saline-alkali land is a major issue in establishing a sustainable agro-ecosystem. To explore the potential of different straw returning in improving saline-alkaline land, we utilized native saline-alkaline soil (SCK), wheat straw-returned saline-alkaline soil (SXM) and rapeseed straw-returned saline-alkaline soil (SYC) as our research objects. Soil physicochemical properties, fungal community structure and diversity of saline-alkaline soils were investigated in different treatments at 0-10 cm, 10-20 cm and 20-30 cm soil depths. The results showed that SXM and SYC reduced soil pH and total salinity but increased soil organic matter, alkali-hydrolyzable nitrogen, available phosphorus, total potassium, etc., and the enhancement effect of SYC was more significant. The total salinity of the 0-10 cm SCK soil layer was much higher than that of the 10-30 cm soil layers. Fungal diversity and abundance were similar in different soil layers in the same treatment. SXM and SYC soil had higher fungal diversity and abundance than SCK. At the genus level, Plectosphaerella, Mortierella and Ascomycota were the dominant groups of fungal communities in SXM and SYC. The fungal diversity and abundance in SXM and SYC soils were higher than in SCK soils. Correlation network analysis of fungal communities with environmental factors showed that organic matter, alkali-hydrolyzable nitrogen and available phosphorus were the main environmental factors for the structural composition of fungal communities of Mortierella, Typhula, Wickerhamomyces, Trichosporon and Candida. In summary, straw returning to the field played an effective role in improving saline-alkaline land, improving soil fertility, affecting the structure and diversity of the fungal community and changing the interactions between microorganisms.
ABSTRACT
The CUP-SHAPED COTYLEDON2 (CUC2) gene plays an important role in the formation of apical meristem and organ edges in plants. The apical meristematic tissue of Brassica rapa (B. rapa) is associated with cold resistance, however, the role of the CUC2 gene in cold resistance of B.rapa is unclear. In this study, we used bioinformatics software to analyze the structure of BrCUC2 gene, real-time fluorescence quantitative PCR to detect the expression level of BrCUC2, constructed transgenic Arabidopsis thaliana by the flower dipping method and subcellular localization for functional validation. The results showed that, we isolated a 1104 bp open reading frame of BrCUC2 from the winter B. rapa cultivar 'Longyou 7'. The BrCUC2 contains a highly conserved domain belonging to the NAM superfamily. Its homologus CUC genes contain similar conserved motifs and are closely related to Brassica oleracea (B.oleracea), and the N-terminal of amino acid sequence contains NAC domain. BrCUC2 protein was localized in the nucleus and self-activation tests showed that pGBKT7-BrCUC2 had self-activation. Tissue-specific expression analysis and promoter ß-Glucuronidase (GUS) activity showed that BrCUC2 had high expression levels in B. rapa growth points and A. thaliana leaf edges, stems and growth points. After low-temperature stress, BrCUC2 showed greater expression in 'Longyou 7,' which presents strong cold resistance and concave growth points, than in 'Longyou 99,' which presents weak cold resistance and protruding growth points. BrCUC2 promoter contains multiple elements related to stress responses. BrCUC2 overexpression revealed that the phenotype did not differ from that of the wild type during the seedling stage but showed weak growth and a dwarf phenotype during the flowering and mature stages. After low-temperature treatment, the physiological indexes and survival rate of BrCUC2-overexpression lines of Arabidopsis thaliana (A. thaliana) were better than those of the wild type within 12 h, although differences were not observed after 24 h. These results showed that BrCUC2 improved the low-temperature tolerance of transgenic A. thaliana within a short time. It can provide a foundation for the study of cold resistance in winter B. rapa.
