Metagenomic insights into the response of rhizosphere microbial to precipitation changes in the alpine grasslands of northern Tibet.

Water changes caused by precipitation may affect the elemental cycle of ecosystems by influencing soil microorganisms. In this study, precipitation control experiment was conducted in semi-arid alpine grasslands in northern Tibet, and plots were set up and divided into increased water (IW) and decreased water (DW) plots. Moreover, the link between functional genes and soil environmental factors, and the responses of the microbial community functions to precipitation-induced water variations were studied using metagenomic sequencing. To clarify the roles of various proteins and metabolites in the semi-arid alpine grasslands of northern Tibet, functional annotations of clusters of orthologous groups of proteins, Kyoto Encyclopedia of Genes and Genomes, and carbohydrate-active enzyme of the sequencing data were conducted. The results showed that the absolute abundance of microbial functional genes in IW was significantly higher than that in the control check (CK, natural precipitation) and DW. However, the absolute abundance did not significantly differ between CK and DW. There was no significant difference among the four plant species (Stipa purpurea, Carex moocroftii, Othropis microphylla, and Artemisia capillaris) considered in this study. These results indicated that microbial functions were mainly affected by water and do not depend on the species, and that the effect of IW was greater than that of DW. Further, we found that soil C, N, K, and other nutrients play vital roles in microbial growth, microbial functional genes were not affected by pH; however, soil C, N, and K nutrients and functional genes were negative correlated. Overall, this study enhances our understanding of the responses of microorganisms to precipitation and can be used as a valuable reference for understanding the drought resistance of soil microorganisms in semi-arid and alpine regions.

Responses of soil bacterial communities to precipitation change in the semi-arid alpine grassland of Northern Tibet.

A change in precipitation can profoundly change the structure of soil microbial communities, especially in arid and semi-arid areas which are limited by moisture conditions. Therefore, it is crucial to explore how soil bacterial community composition and diversity will respond to variation in precipitation. Here we conducted a precipitation control experiment to simulate precipitation change by reducing and increasing rainfall by 25%, 50%, and 75% in the alpine grasslands of northern Tibet. The composition, diversity, and species interaction network of soil microbial community were studied by high-throughput sequencing, and the relationship between microbial community species and soil environmental factors was analyzed. Our results showed that Proteobacteria (45%-52%) and Actinobacteria (37%-45%) were the dominant bacteria in the soil. The alpha diversity index based on Shannon, Chao1, and Simpson indices revealed that precipitation change had no significant effect on richness and evenness of soil microbial communities. Non-metric multidimensional scaling (NMDS) and analysis of similarities (ANOSIM) showed that a clear separation of soil microbial communities between D2(-50%),D3(-75%) and W2(+50%), W3(+75%) treatments. The microbial interaction network indicated that the water-increasing treatment group had closer connections, and Proteobacteria and Actinomycetes were the core species. Furthermore, there was a stronger positive correlation between species in the water-reducing treatment group, the contribution of Proteobacteria decreased significantly, the role of connecting hub decreased, and Actinomycetes became the most important core microbial species. In addition, soil water content (SWC) and available phosphorus (AP) were closely related to the variations in soil microbial compositions. The findings of this study provide a theoretical basis for the driving mechanism of global climate change on soil microbial community and grassland ecosystem in alpine grassland.

Rhizosphere soil microbial community and its response to different utilization patterns in the semi-arid alpine grassland of northern Tibet.

As the link between plants and soils, rhizosphere soil microorganisms play an important role in the element cycle. This study aimed to understand the response of the rhizosphere soil microbial community structure and interaction network to grassland utilization in the alpine steppe of the northern Tibet Plateau. High-throughput sequencing was employed to study the composition, diversity, and species interaction network of rhizosphere soil microbial communities under grazing, mowing, and enclosing treatments. Proteobacteria (47.19%) and Actinobacteria (42.20%) were the dominant bacteria in the rhizosphere soil. There was no significant difference in relative abundance among rhizosphere soil microorganisms at phylum and genus levels, but differences were found in Chlorobi, Ignavibacteriae, and Micromonospora. The alpha diversity index based on Shannon, Chao1, and Simpson indices revealed that except for a significant difference in the Shannon index of the Artemisia nanschanica group, the richness and evenness of rhizosphere soil microbial communities among all groups were similar. Non-metric multidimensional scaling (NMDS) and multi-response permutation procedure (MRPP) analyses showed that the inter-group differences of three plants (Stipa purpurea, Carex moorcroftii, and Artemisia nanschanica) were greater than the differences within the groups; however, only the inter-group difference with the Stipa purpurea group was significant. The microbial interaction network showed that the network complexity of the Artemisia nanschanica group and the enclosing treatment, which were not easily influenced by external factors, were higher than those of the other groups and treatments; this again demonstrated that Proteobacteria and Actinobacteria were the network core microbial species in alpine steppe of the northern Tibet Plateau and were crucial for maintaining stability of the microbial communities. Findings from this study provide a theoretical basis for the restoration of degraded alpine grassland and the development of microbial functions.

Wax composition and concentration in jujube (Ziziphus jujuba Mill.) cultivars with differential resistance to fruit cracking.

Fruit cracking is a key problem restricting the development of the jujube (Ziziphus jujuba) industry, and is closely related to the distribution of the wax layer on the surface of the fruit. Three jujube cultivars with different levels of cracking resistance, namely 'Popozao', 'Banzao', and 'Hupingzao', were selected for comparison. Cracks on the cuticular membrane (CM) of 'Hupingzao' widened and deepened during the coloring period. The wax level of highly cracking-resistant 'Popozao' was significantly higher than that of 'Hupingzao' during the fruit coloring period. The fruit wax composition of the three jujube cultivars were quite similar, consisting mainly of alkanes, triterpenoids, aldehydes, amines, phenols, esters, ketones, fatty acids, primary alcohols, and other, unclassified compounds. Fatty acids, primary alcohols, and alkanes were the predominant fruit wax compounds of the three cultivars. We further analyzed the carbon chain length of aliphatic compounds and found that the concentration of fatty acids in 'Popozao' was significantly lower than that in 'Banzao' and 'Hupingzao' during the coloring period. Moreover, C28-30 were the most abundant primary alcohols during fruit development. Highly cracking-resistant cultivar 'Popozao' contains more very-long-chain alkanes and aldehydes (carbon atom >20) than 'Banzao' and 'Hupingzao' during the coloring period. In addition, we assessed the expression levels of 11 genes involved in fatty acid biosynthesis, elongation, and degradation, and in wax biosynthesis. Gene expression analysis indicated that KCS1, CER1, CYP86B1, and CYP86A play crucial roles in wax formation on jujube fruit. In conclusion, fruit cracking was correlated with whether wax synthesis is coordinated with fruit enlargement and'Popozao' has a stronger ability to synthesize very-long-chain alkanes and aldehydes. Understanding the diff ;erences in the cuticular wax and the activities of the corresponding genes in jujube cultivars with different sensitivities to cracking will provide a specific way to prevent fruit cracking.

[The quality control of carbonized cortex moutan].

OBJECTIVE: To set up method for the quality control of carbonized Cortex Moutan. METHODS: The optimized processing technology of carbonized Cortex Moutan was selected by the time of blood coagulation. Besides, the contents of tannin, adsorbability, paeonol and peoniflorin were researched. RESULTS: To parch the pieces 5 minutes at the temperature of 22 degrees C was the optimized processing technology. CONCLUSION: This study provides a reference to the institution for the quality standard of carbonized Cortex Moutan.