Root-knot nematodes (RKNs; genus Meloidogyne) are a class of plant parasites that infect the roots of many plant species. It is believed that RKNs target certain signaling molecules derived from plants to locate their hosts; however, currently, no plant compound has been unambiguously identified as a universal RKN attractant. To address this question, we screened a chemical library of synthetic compounds for Meloidogyne incognita attractants. The breakdown product of aminopropylamino-anthraquinone, 1,3-diaminopropane, as well as its related compounds, putrescine and cadaverine, were found to attract M. incognita. After examining various polyamines, M. incognita were found to be attracted specifically by natural compounds that possess three to five methylene groups between two terminal amino groups. Using cryo-TOF-SIMS/SEM, cadaverine was indeed detected in soybean root cortex cells and the surrounding rhizosphere, establishing a chemical gradient. In addition to cadaverine, putrescine and 1,3-diaminopropane were also detected in root exudate by HPLC-MS/MS. Furthermore, exogenously applied cadaverine is sufficient to enhance M. incognita infection of Arabidopsis seedlings. These results suggest that M. incognita is likely attracted by polyamines to locate the appropriate host plants, and the naturally occurring polyamines have potential applications in agriculture in developing protection strategies for crops from RKN infection.

Finding prey is essential to survival, with marine predators hypothesised to track chemicals such as dimethyl sulfide (DMS) while foraging. Many predators are attracted to artificially released DMS, and laboratory experiments have shown that zooplankton grazing on phytoplankton accelerates DMS release. However, whether natural DMS concentrations are useful for predators and correlated to areas of high prey biomass remains a fundamental knowledge gap. Here, we used concurrent hydroacoustic surveys and in situ DMS measurements to present evidence that zooplankton biomass is spatially correlated to natural DMS concentration in air and seawater. Using agent simulations, we also show that following gradients of DMS would lead zooplankton predators to areas of higher prey biomass than swimming randomly. Further understanding of the conditions and scales over which these gradients occur, and how they are used by predators, is essential to predicting the impact of future changes in the ocean on predator foraging success.

Diamines, such as 1,3-diaminopropane (Dap), 1,4-diaminobutane (putrescine, or Put), and 1,5-diaminopentane (cadaverine), are essential organic bases for plants. Such “biogenic diamines” are abundantly present in oak tree flowers and are emitted into the atmosphere. We sampled atmospheric diamines in a typical broadleaf tree forest and chestnut grove during blossom season and carried out a chromatography-mass spectrometry analysis. Amide derivatives of Dap and Put, 3-aminopropanamide and 4-aminobutanamide, respectively, were found in higher atmospheric concentrations than their source diamine. Because their concentrations in oak tree flowers were very low, we deduced that these aminoamides were produced after Dap and Put, respectively, were released into the atmosphere. Time series of biogenic diamine and aminoamide concentrations showed evidence of diurnal variations. Concentrations were lower during daytime in sunny conditions, suggesting relatively fast photochemical decomposition. Biogenic diamines and aminoamides bond more easily than monoamines with water vapor and sulfuric acid in the atmosphere. Biogenic diamines and aminoamides may play a role in the formation of new particles and biogenic secondary organic aerosols in the forest atmosphere during spring and early summer.

bSexual reproduction is essential for the maintenance of species in a wide variety of multicellular organisms, and even unicellular organisms that normally proliferate asexually possess a sexual cycle because of its contribution to increased genetic diversity. Information concerning the molecules involved in fertilization is accumulating for many species of the metazoan, plant, and fungal lineages, and the evolutionary consideration of sexual reproduction systems is now an interesting issue. Macrocyst formation in the social amoeba Dictyostelium discoideum is a sexual process in which cells become sexually mature under dark and submerged conditions and fuse with complementary mating-type cells. In the present study, we isolated D. discoideum insertional mutants defective in sexual cell fusion and identified the relevant gene, macA, which encodes a highly glycosylated, 2,041-amino-acid membrane protein (MacA). Although its overall similarity is restricted to proteins of unknown function within dictyostelids, it contains LamGL and discoidin domains, which are implicated in cell adhesion. The growth and development of macA-null mutants were indistinguishable from those of the parental strain. The overexpression of macA using the V18 promoter in a macA-null mutant completely restored its sexual defects. Although the macA gene encoded exactly the same protein in a complementary mating-type strain, it was expressed at a much lower level. These results suggest that MacA is indispensable for gamete interactions in D. discoideum, probably via cell adhesion. There is a possibility that it is controlled in a mating-typedependent manner.

Plant materials and growth conditions. All Arabidopsis thaliana plants used in this study are of the Col-0 ecotype background. The mutant line, del1-1, was obtained from the Arabidopsis Biological Resource Center (ABRC). Arabidopsis seeds were stratified for 2 days in 4 °C in the dark, then allowed to germinate and grown for 5 days on 0.25 × Murashige and Skoog (MS) salt mixture (Sigma), 0.5% (w/v) sucrose, and 0.6% (w/v) gellan gum at pH 6.4 under continuous light at 23 °C.