Keeping the doors open for symbiosis: Nitrogen fixation by legumes results from a symbiotic partnership between plant and microbes. These together elaborate nodules on the plant roots that house the bacteria. Tsikou et al. identified a microRNA made in the aboveground shoots of Lotus japonicus that translocates to the plant's roots. In the roots, the microRNA posttranscriptionally regulates a key suppressor of symbiosis, thus keeping the uninfected root susceptible to productive infection by symbiotic bacteria. Science , this issue p. 233

Background and Aims Despite their importance in many aspects of plant physiology, information about the function of oxidative and, particularly, of nitrosative signalling in fruit biology is limited. This study examined the possible implications of O₃ and sodium nitroprusside (SNP) in kiwifruit ripening, and their interacting effects. It also aimed to investigate changes in the kiwifruit proteome in response to SNP and O₃ treatments, together with selected transcript analysis, as a way to enhance our understanding of the fruit ripening syndrome. Methods Kiwifruits following harvest were pre-treated with 100 μm SNP, then cold-stored (0 °C, relative humidity 95 %) for either 2 or 6 months in the absence or in the presence of O₃ (0·3 μL L^–1), and subsequently were allowed to ripen at 20 °C. The ripening behaviour of fruit was characterized using several approaches: together with ethylene production, several genes, enzymes and metabolites involved in ethylene biosynthesis were analysed. Kiwifruit proteins were identified using 2-D electrophoresis coupled with nanoliquid chromatography–tandem mass spectrometry (LC-MS/MS) analysis. Expression patterns of kiwifruit ripening-related genes were also analysed using real-time quantitative reverse transcription–PCR (RT–qPCR). Key Results O₃ treatment markedly delayed fruit softening and depressed the ethylene biosynthetic mechanism. Although SNP alone was relatively ineffective in regulating ripening, SNP treatment prior to O₃ exposure attenuated the O₃-induced ripening inhibition. Proteomic analysis revealed a considerable overlap between proteins affected by both SNP and O₃. Consistent with this, the temporal dynamics in the expression of selected kiwifruit ripening-related genes were noticeably different between individual O₃ and combined SNP and O₃ treatments. Conclusions This study demonstrates that O₃-induced ripening inhibition could be reversed by SNP and provides insights into the interaction between oxidative and nitrosative signalling in climacteric fruit ripening.

A lepidopteran insect cell-based expression system has been employed to express three Anopheles gambiae odorant receptors (ORs), OR1 and OR2, which respond to components of human sweat, and OR7, the ortholog of Drosophila's OR83b, the heteromerization partner of all functional ORs in that system. With the aid of epitope tagging and specific antibodies, efficient expression of all ORs was demonstrated and intrinsic properties of the proteins were revealed. Moreover, analysis of the orientation of OR1 and OR2 on the cellular plasma membrane through the use of a novel ‘topology screen’ assay and FACS analysis demonstrates that, as was recently reported for the ORs in Drosophila melanogaster, mosquito ORs also have a topology different than their mammalian counterparts with their N-terminal ends located in the cytoplasm and their C-terminal ends facing outside the cell. These results set the stage for the production of mosquito ORs in quantities that should permit their detailed biochemical and structural characterization and the exploration of their functional properties.