iTRAQ Protein Profile Differential Analysis of Dormant and Germinated Grassbur Twin Seeds Reveals that Ribosomal Synthesis and Carbohydrate Metabolism Promote Germination Possibly Through the PI3K Pathway.

Grassbur is a destructive and invasive weed in pastures, and its burs can cause gastric damage to animals. The strong adaptability and reproductive potential of grassbur are partly due to a unique germination mechanism whereby twin seeds develop in a single bur: one seed germinates, but the other remains dormant. To investigate the molecular mechanism of seed germination in twin seeds, we used isobaric tags for relative and absolute quantitation (iTRAQ) to perform a dynamic proteomic analysis of germination and dormancy. A total of 1,984 proteins were identified, 161 of which were considered to be differentially accumulated. The differentially accumulated proteins comprised 102 up-regulated and 59 down-regulated proteins. These proteins were grouped into seven functional categories, ribosomal proteins being the predominant group. The authenticity and accuracy of the results were confirmed by enzyme-linked immunosorbent assay (ELISA) and quantitative real-time reverse transcription-PCR (qPCR). A dynamic proteomic analysis revealed that ribosome synthesis and carbohydrate metabolism affect seed germination possibly through the phosphoinositide 3-kinase (PI3K) pathway. As the PI3K pathway is generally activated by insulin, analyses of seeds treated with exogenous insulin by qPCR, ELISA and iTRAQ confirmed that the PI3K pathway can be activated, which suppresses dormancy and promotes germination in twin grassbur seeds. Together, these results show that the PI3K pathway may play roles in stimulating seed germination in grassbur by modulating ribosomal synthesis and carbohydrate metabolism.

[Effects of Vegetation Restoration on the Structure and Function of the Rhizosphere Soil Bacterial Community of Solanum rostratum].

Invasive plants can change soil microbial communities and therefore promote invasion. While vegetation restoration has been adopted in certain infested lands to curb the invasion of Solanum rostratum, changes in the composition and function of rhizosphere soil bacterial communities of the species before and after the restoration has not yet been reported. In this study, two vegetation combinations used in previous studies were selected as candidates:Astragalus adsurgens+Elymus dahuricus+Bromus inermis (T1) and A. adsurgens+Festuca arundinacea+Agropyron cristatum+Leymus chinensis (T2). Rhizosphere soil samples were collected from each combination (T1 and T2), a S. rostratum invaded area (SR), and the native plant (NP) control to analyze the bacterial community structure and diversity using 16S rDNA gene sequencing on the Illumina MiSeq platform. PICRUSt was further used to predict the functional abilities of soil bacterial communities. Results of 16S rDNA gene sequencing showed that both the Simpson and Chao1 indices were higher in the SR treatment than in the NP treatment, but neither reached a significant level, although both indices decreased significantly after vegetation restoration (T1 and T2; P<0.05). The relative abundance of Microvirga, Skermanella, and Sphingomonas from phylum Proteobacteria and Bryobacter from the phylum Acidobacteria were significantly lower in the SR treatment (P<0.05) when compared with the NP treatment and higher in restoration treatments (T1 and T2). The RDA analysis showed that soil organic matter (OM), total nitrogen (TN), total phosphorus (TP), total potassium (TK), and available potassium (AK) were important factors affecting the composition of the bacterial community. Based on the PICRUSt analysis of soil bacterial community functions, the relative abundance of gene families related to biosynthesis of amino acids, purine metabolism, pyrimidine metabolism, ribosome, and aminoacyl-tRNA biosynthesis were higher in the rhizosphere samples of the SR treatment than those of the NP treatment and reduced significantly after vegetation restoration (T1 and T2; P<0.05). The structure and function of rhizosphere soil bacterial community of S. rostratum and vegetation restoration were analyzed and provided a theoretical basis for the invasion mechanism and ecological restoration of S. rostratum.

[Effects of invasive Cenchrus spinifex on nitrogen pools in sandy grassland]. / å°‘èŠ±è’ºè—œè‰å ¥ä¾µå¯¹æ²™è´¨è‰åœ°æ°®åº“çš„å½±å“.

Cenchrus spinifex is an invasive plant found in large areas of northern China. In this study, we focused on analysis of the effects of C. spinifex on soil nitrogen and plant nitrogen pools in Horqin sandy grassland. In addition, a pot experiment with 15N tracing techniques was designed to study the biological nitrogen fixation ability of C. spinifex, compared with two native grasses, Elymus dahuricus and Agropyron cristatum. The total soil nitrogen pool in C. spinifex invaded-area increased significantly by 47.5% and 20.8%, and the soil ammonium nitrogen pool decreased significantly by 25.6% and 25.2%, compared with those in bare and native plant Roegneria kamoji areas, respectively. The plant shoot nitrogen pool decreased significantly by 18.7% in C. spinifex compared with native plant R. kamoji. Atom% 15N, atom% 15N excess and atom% 15N weighting excess of C. spinifex were all significantly lower than those of E. dahuricus and A. cristatum. The nitrogen use efficiencies of C. spinifex and E. dahuricus were 48.5% and 47.0%, respectively, and no significant difference was observed. Ndfa of C. spinifex accounted for 60.2%, when growing together with E. dahuricus. These results suggested that the characteristics on the high efficient use for nitrogen of this invasive weed might an ecological adaptation mechanism, leading to successful colonization and spread in Horqin Steppe.

[Effects of Flaveria bidentis invasion on the diversity of functional bacteria in rhizosphere soil.] / é»„é¡¶èŠå ¥ä¾µå¯¹åœŸå£¤ä¸­ä¸»è¦åŠŸèƒ½ç»†èŒçš„å½±å“.

Flaveria bidentis is an invasive plant found in large areas of northern China. This study conducted a separation and screening of the main functional bacteria in the soil of F. bidentis and investigated the change in the community structure. A variety of functional microbes were isolated using selective media and rep-PCR clustering, and a diversity analysis was carried out. In addition, the dominant populations of various functional bacteria were identified using 16S rRNA sequence alignment. The results showed that F. bidentis increased the contents of the major available nutrients in the soil, and the levels of azotobacteria, organic phosphorus bacteria, inorganic phosphorus bacteria, and silicate bacteria in the soil of F. bidentis were significantly higher than those of the native plant Tagetes erecta and the control. rep-PCR analysis indicated that the structure of the four functional bacterial microfloras in the soil of F. bidentis was significantly different from those of the native plant and control. The diversity analysis demonstrated that the diversity of functional microorganisms in the soil of F. bidentis was richer, the community structure was more complex, the predominant microflora comprised a greater proportion of the total population, and the ecological diversity was higher. This was further evidenced by identification of the main functional isolates from the three soil samples. Our findings indicated a mechanism of invasion by F. bidentis.