SignificanceDrought remains a critical obstacle to meeting the food demands of the coming century. Understanding the interplay between drought stress, plant development, and the plant microbiome is central to meeting this challenge. Here, we demonstrate that drought causes enrichment of a distinct set of microbes in roots, composed almost entirely of monoderms, which lack outer membranes and have thick cell walls. We demonstrate that under drought, roots increase the production of many metabolites, and that monoderms inhabiting the drought-treated rhizosphere exhibit increased activity of transporters connected with some of these same compounds. The discovery of this drought-induced enrichment and associated shifts in metabolite exchange between plant and microbe reveal a potential blueprint for manipulating plant microbiomes for improved crop fitness.

Background The plant microbiome is an integral part of the host and increasingly recognized as playing fundamental roles in plant growth and health. Increasing evidence indicates that plant rhizosphere recruits beneficial microbes to the plant to suppress soil-borne pathogens. However, the ecological processes that govern plant microbiome assembly and functions in the below- and aboveground compartments under pathogen invasion are not fully understood. Here, we studied the bacterial and fungal communities associated with 12 compartments (e.g., soils, roots, stems, and fruits) of chili pepper (Capsicum annuum L.) using amplicons (16S and ITS) and metagenomics approaches at the main pepper production sites in China and investigated how Fusarium wilt disease (FWD) affects the assembly, co-occurrence patterns, and ecological functions of plant-associated microbiomes. Results The amplicon data analyses revealed that FWD affected less on the microbiome of pepper reproductive organs (fruit) than vegetative organs (root and stem), with the strongest impact on the upper stem epidermis. Fungal intra-kingdom networks were less stable and their communities were more sensitive to FWD than the bacterial communities. The analysis of microbial interkingdom network further indicated that FWD destabilized the network and induced the ecological importance of fungal taxa. Although the diseased plants were more susceptible to colonization by other pathogenic fungi, their below- and aboveground compartments can also recruit potential beneficial bacteria. Some of the beneficial bacterial taxa enriched in the diseased plants were also identified as core taxa for plant microbiomes and hub taxa in networks. On the other hand, metagenomic analysis revealed significant enrichment of several functional genes involved in detoxification, biofilm formation, and plant-microbiome signaling pathways (i.e., chemotaxis) in the diseased plants. Conclusions Together, we demonstrate that a diseased plant could recruit beneficial bacteria and mitigate the changes in reproductive organ microbiome to facilitate host or its offspring survival. The host plants may attract the beneficial microbes through the modulation of plant-microbiome signaling pathways. These findings significantly advance our understanding on plant-microbiome interactions and could provide fundamental and important data for harnessing the plant microbiome in sustainable agriculture.

Arbuscular mycorrhizal (AM) fungi form symbiotic associations with most plant species in terrestrial ecosystems, and are affected by environmental variations. To reveal the impact of disturbance on an AM fungal community under future global warming, we examined the abundance and community composition of AM fungi in both soil and mixed roots in an alpine meadow on the Qinghai-Tibetan Plateau, China. Warming and grazing had no significant effect on AM root colonization, spore density and extraradical hyphal density. A total of 65 operational taxonomic units (OTUs) of AM fungi were identified from soil and roots using molecular techniques. AM fungal OTU richness was higher in soil (54 OTUs) than in roots (34 OTUs), and some AM fungi that differed between soil and roots, showed significantly biased occurrence to warming or grazing. Warming and grazing did not significantly affect AM fungal OTU richness in soil, but warming with grazing significantly increased AM fungal OTU richness in roots compared to the grazing-only treatment. Non-metric multidimensional scaling analysis showed that the AM fungal community composition was significantly different between soil and roots, and was significantly affected by grazing in roots, whereas in soil it was significantly affected by warming and plant species richness. The results suggest that the AM fungal community responds differently to warming and grazing in soil compared with roots. This study provides insights into the role of AM fungi under global environmental change scenarios in alpine meadows of the Qinghai-Tibetan Plateau.

Elucidating the responses of soil microbial abundance and community composition to nitrogen (N) addition is important for predicting ecosystem function under increased atmospheric N deposition. We examined the arbuscular mycorrhizal (AM) fungal community under three N forms (NH4(+)-N, NO3(-)-N, and NH4NO3-N) and two N rates (1.5 and 7.5 g N m(-2) year(-1)) in an alpine meadow of the Qinghai-Tibetan Plateau. AM fungal extraradical hyphal density was significantly decreased by NH4(+)-N in May, but was not affected by N form nor N rate in August. N rate, but not N form, significantly affected AM fungal spore density; high N rate decreased spore density. No direct N addition effect was observed on AM fungal community; however, soil available phosphorus, pH, and NO3(-)-N were considered as important factors that influenced AM fungal community composition. Structural equation model results showed that N rate, not N form, strongly affected soil characteristics, which directly influenced community compositions of plants and AM fungi, as well as spore density. Therefore, AM fungal community was influenced by N addition, primarily because of altered soil characteristics, and partially by a modified plant community, but not or just slightly by direct N addition effects in this alpine meadow ecosystem.

Background: Plant microbiome is an integral part of the host influencing its growth and health. The increasing evidence indicates that plant rhizosphere may recruit beneficial microbes to suppress soil-borne pathogen, but the ecological mechanisms that govern plant microbiome assembly and functions under disease in both below and aboveground compartments are not fully understood. Here we examined both bacterial and fungal communities from soils (rhizosphere and bulk soil) and multiple plant compartments (e.g. root, stem, and fruit) of chili pepper (Capsicum annuum L.) at two pepper production sites, and explored how Fusarium wilt disease (FWD) affect the assembly, co-occurrence patterns, and ecological functions of plant-associated microbiomes. Results: Our data demonstrated that FWD had less impact on reproductive organ (fruit) than on vegetative organs (root and stem), with the strongest impact in the stem upper epidermis. Fungal intra-kingdom networks presented lower stabilities and their communities were more sensitive to FWD than the bacterial communities. Moreover, the diseased pepper was more susceptible to colonization by other pathogenic fungi, but they may recruit potential beneficial bacteria to facilitate host or offspring survival, and FWD may enhance the ecological importance of fungal taxa in the interkingdom network. Further, metagenomic analysis revealed that several potential protective functional genes encoding detoxify and biofilm formation were significantly enriched in the diseased pepper.Conclusion: Together, these results significantly advance our understanding of pepper microbiome assembly and functions under biotic stress. Our work highlights the diseased plant and the aboveground compartments harbor a potential of beneficial microbiomes and functions that, in concert, can provide potential critical data for harnessing the plant microbiome for sustainable agriculture.

Micromelum falcatum (LOUR.) TAN. (Rutaceae), traditionally used as Chinese folk medicine for curing infected wounds, odynolysis, and rheumatism, is widely distributed in Southeast Asia. The chemical constituents of M. falcatum had been previously investigated, and several coumarins, dihydrocinnamic acid derivatives, and two alkaloids 5,6-pyranoglycozoline and yuehchukene were obtained.1,2) The dimeric indole alkaloid yuehchukene was found to have potent anti-implantation activity.3) After further chemical investigation on the stem bark of M. falcatum, we report here the isolation of two new quinoldione alkaloids, methyl 2-(3-hydroxy-1-methyl-2,4-dioxo-1,2,3,4-tetrahydroquinolin-3-yl)acetate (1) and 3-hydroxy-1-methyl-3-(2-oxopropyl)-quinoline-2,4(1H,3H)-dione (2), two quinolinone alkaloids previously synthesized but first isolated as natural products, N-methylflindersine (3) 4,5) and 4-hydroxy-3-methoxy-1-methyl-2(1H)-quinolinone (4), 6) and the known N-methylswietenidine-B (5).7) All isolates were tested for toxicity towards brine shrimp larvae.

New values of parameters a and b are proposed for the CIE system of mesopic photometry MES2 [CIE Publication 191:2010], because from the original values this model may have no solution or multi-solutions. From the new values of parameters a and b it is shown that the CIE MES2 system has a unique solution. The difference however, between the original and the new values of parameters a and b is very small and the changes do not affect previous conclusions based on the MES2 model. To compute such a solution, we propose a Bisection-Newton method which exhibits fast convergence (8 iterations in the worst case), and improves the fixed-point method recommended by the CIE MES2 system, which has convergence problems for high values of the photopic luminance and very high values of the scotopic/photopic ratio. Comparative results for the fixed-point method, the Bisection method, the Newton method, and the Bisection-Newton method, in terms of the number of iterations necessary for convergence and the computation time used, are reported.

This study analyzes the differences between the category structure of the Universal Decimal Classification (UDC) system (which is one of the widely used library classification systems in Europe) and Wikipedia. In particular, we compare the emerging structure of category-links to the structure of classes in the UDC. With this comparison we would like to scrutinize the question of how do knowledge maps of the same domain differ when they are created socially (i.e. Wikipedia) as opposed to when they are created formally (UDC) using classification theory. As a case study, we focus on the category of "Arts".In modern times, the fast expansion of human knowledge makes categories a necessity in managing and accessing produced knowledge. The science of 'knowledge orders', i.e. taxonomies, classifications, etc., is born out of this need. However today, with all the tools the information society has to offer, taxonomies have a powerful opponent: folksonomies.Folksonomies are an outcome of the phenomenon of collective writing, and collaborative tagging. Wikipedia is one favorite object for studying such behavior. For a long time, Wikipedia relied only on search engines for information retrieval, and its users browsed the content by following simple links (called