Differential effects of winter cold stress on soil bacterial communities, metabolites, and physicochemical properties in two varieties of Tetrastigma hemsleyanum Diels & Gilg in reclaimed land.

Tetrastigma hemsleyanum Diels & Gilg (TDG) has been recently planted in reclaimed lands in Zhejiang Province, China, to increase reclaimed land use. Winter cold stress seriously limits the growth and development of TDG and has become the bottleneck limiting the TDG planting industry. To investigate the defense mechanisms of TDG toward winter cold stress when grown on reclaimed land, a combined analysis of soil bacterial communities, metabolites, and physicochemical properties was conducted in this study. Significant differences were observed in the composition of soil bacterial communities, metabolites, and properties in soils of a cold-tolerant variety (A201201) compared with a cold-intolerant variety (B201810). The fresh weight (75.8% of tubers) and dry weight (73.6%) of A201201 were significantly higher than those of B201810. The 16S rRNA gene amplicon sequencing of soil bacteria showed that Gp5 (25.3%), Gemmatimonas (19.6%), Subdivision3 (16.7%), Lacibacterium (11.9%), Gp4 (11.8%), Gp3 (10.4%), Gp6 (7.0%), and WPS-1 (1.2%) were less common, while Chryseolinea (10.6%) were more common in A201201 soils than B201810 soils. Furthermore, linear discriminant analysis of effect size identified 35 bacterial biomarker taxa for both treatments. Co-occurrence network analyses also showed that the structures of the bacterial communities were more complex and stable in A201201 soils compared to B201810 soils. In addition, ultra-high-performance liquid chromatography coupled to mass spectrometry analysis indicated the presence of significantly different metabolites in the two soil treatments, with 10 differentially expressed metabolites (DEMs) (8 significantly upregulated by 9.2%-391.3% and 2 significantly downregulated by 25.1%-73.4%) that belonged to lipids and lipid-like molecules, organic acids and derivatives, and benzenoids. The levels of those DEMs were significantly correlated with the relative abundances of nine bacterial genera. Also, redundancy discriminant analysis revealed that the main factors affecting changes in the bacterial community composition were available potassium (AK), microbial biomass nitrogen (MBN), microbial biomass carbon (MBC), alkaline hydrolysis nitrogen (AHN), total nitrogen (TN), available phosphorus (AP), and soil organic matter (SOM). The main factors affecting changes in the metabolite profiles were AK, MBC, MBN, AHN, pH, SOM, TN, and AP. Overall, this study provides new insights into the TDG defense mechanisms involved in winter cold stress responses when grown on reclaimed land and practical guidelines for achieving optimal TDG production.IMPORTANCEChina has been undergoing rapid urbanization, and land reclamation is regarded as a viable option to balance occupation and compensation. In general, the quality of reclaimed land cannot meet plant or even cultivation requirements due to poor soil fertility and high gravel content. However, Tetrastigma hemsleyanum Diels & Gilg (TDG), extensively used in Chinese herbal medicine, can grow well in stony soils with few nutrients. So, to increase reclaimed land use, TDG has been cultivated on reclaimed lands in Zhejiang Province, China, recently. However, the artificial cultivation of TDG is often limited by winter cold stress. The aim of this study was to find out how TDG on reclaimed land deal with winter cold stress by looking at the bacterial communities, metabolites, and physicochemical properties of the soil, thereby guiding production in practice.

Role of plant metabolites in the formation of bacterial communities in the rhizosphere of Tetrastigma hemsleyanum.

Tetrastigma hemsleyanum Diels et Gilg, commonly known as Sanyeqing (SYQ), is an important traditional Chinese medicine. The content of bioactive constituents varies in different cultivars of SYQ. In the plant growth related researches, rhizosphere microbiome has gained significant attention. However, the role of bacterial communities in the accumulation of metabolites in plants have not been investigated. Herein, the composition of bacterial communities in the rhizosphere soils and the metabolites profile of different SYQ cultivars' roots were analyzed. It was found that the composition of microbial communities varied in the rhizosphere soils of different SYQ cultivars. The high abundance of Actinomadura, Streptomyces and other bacteria was found to be associated with the metabolites profile of SYQ roots. The findings suggest that the upregulation of rutin and hesperetin may contribute to the high bioactive constituent in SYQ roots. These results provide better understanding of the metabolite accumulation pattern in SYQ, and also provide a solution for enhancing the quality of SYQ by application of suitable microbial consortia.

Comparative proteomic analysis of Arabidopsis mature pollen and germinated pollen.

Proteomic analysis was applied to generating the map of Arabidopsis mature pollen proteins and analyzing the differentially expressed proteins that are potentially involved in the regulation of Arabidopsis pollen germination. By applying 2-D electrophoresis and silver staining, we resolved 499 and 494 protein spots from protein samples extracted from pollen grains and pollen tubes, respectively. Using the matrix-assisted laser desorption ionization time-of-flight mass spectrometry method, we identified 189 distinct proteins from 213 protein spots expressed in mature pollen or pollen tubes, and 75 new identified proteins that had not been reported before in research into the Arabidopsis pollen proteome. Comparative analysis revealed that 40 protein spots exhibit reproducible significant changes between mature pollen and pollen tubes. And 21 proteins from 17 downregulated and six upregulated protein spots were identified. Functional category analysis indicated that these differentially expressed proteins mainly involved in signaling, cellular structure, transport, defense/stress responses, transcription, metabolism, and energy production. The patterns of changes at protein level suggested the important roles for energy metabolism-related proteins in pollen tube growth, accompanied by the activation of the stress response pathway and modifications to the cell wall.