Arbuscular mycorrhizal (AM) fungi are important members of the root microbiome and may be used as biofertilizers for sustainable agriculture. To elucidate the impact of AM fungal inoculation on indigenous root microbial communities, we used high-throughput sequencing and an analytical pipeline providing fixed operational taxonomic units (OTUs) as an output to investigate the bacterial and fungal communities of roots treated with a commercial AM fungal inoculum in six agricultural fields. AM fungal inoculation significantly influenced the root microbial community structure in all fields. Inoculation changed the abundance of indigenous AM fungi and other fungal members in a field-dependent manner. Inoculation consistently enriched several bacterial OTUs by changing the abundance of indigenous bacteria and introducing new bacteria. Some inoculum-associated bacteria closely interacted with the introduced AM fungi, some of which belonged to the genera Burkholderia , Cellulomonas , Microbacterium , Sphingomonas , and Streptomyces and may be candidate mycorrhizospheric bacteria that contribute to the establishment and/or function of the introduced AM fungi. Inoculated AM fungi also co-occurred with several indigenous bacteria with putative beneficial traits, suggesting that inoculated AM fungi may recruit specific taxa to confer better plant performance. The bacterial families Methylobacteriaceae , Acetobacteraceae , Armatimonadaceae , and Alicyclobacillaceae were consistently reduced by the inoculation, possibly due to changes in the host plant status caused by the inoculum. To the best of our knowledge, this is the first large-scale study to investigate interactions between AM fungal inoculation and indigenous root microbial communities in agricultural fields.

Aim Lotus japonicus is a herbaceous perennial legume that has been used extensively as a genetically tractable model system for deciphering the molecular genetics of symbiotic nitrogen fixation. Our aim is to improve the L. japonicus reference genome sequence, which has so far been based on Sanger and Illumina sequencing reads from the L. japonicus accession MG-20 and contained a large fraction of unanchored contigs. Methods and Results Here, we use long PacBio reads from L. japonicus Gifu combined with Hi-C data and new high-density genetic maps to generate a high-quality chromosome-scale reference genome assembly for L. japonicus. The assembly comprises 554 megabases of which 549 were assigned to six pseudomolecules that appear complete with telomeric repeats at their extremes and large centromeric regions with low gene density. Conclusion and Perspectives The new L. japonicus Gifu reference genome and associated expression data represent valuable resources for legume functional and comparative genomics. Here, we provide a first example by showing that the symbiotic islands recently described in Medicago truncatula do not appear to be conserved in L. japonicus.

Background Genomic information for Allium cepa L. is limited as it is heterozygous and its genome is very large. To elucidate potential SNP markers obtained by NGS, we used a complete set of A. fistulosum L.-A. cepa monosomic addition lines (MALs) and doubled haploids (DHs). These were the parental lines of an A. cepa mapping population for transcriptome-based SNP genotyping. Results We mapped the transcriptome sequence reads from a series of A. fistulosum-A. cepa MALs onto the unigene sequence of the doubled haploid shallot A. cepa Aggregatum group (DHA) and compared the MAL genotype call for parental bunching onion and shallot transcriptome mapping data. We identified SNP sites with at least four reads on 25,462 unigenes. They were anchored on eight A. cepa chromosomes. A single SNP site was identified on 3,278 unigenes and multiple SNPs were identified on 22,184 unigenes. The chromosome marker information was made public via the web database Allium TDB (http://alliumtdb.kazusa.or.jp/). To apply transcriptome based genotyping approach for genetic mapping, we gathered RNA sequence data from 96 lines of a DHA × doubled haploid bulb onion A. cepa common onion group (DHC) mapping population. After selecting co-dominant SNP sites, 16,872 SNPs were identified in 5,339 unigenes. Of these, at least two SNPs with identical genotypes were found in 1,435 unigenes. We developed a linkage map using genotype information from these unigenes. All unigene markers mapped onto the eight chromosomes and graphical genotyping was conducted based on the unigene order information. Another 2,963 unigenes were allocated onto the eight chromosomes. To confirm the accuracy of this transcriptome-based genetic linkage map, conventional PCR-based markers were used for linkage analysis. All SNP - and PCR-based markers were mapped onto the expected linkage groups and no inconsistency was found among these chromosomal locations. Conclusions Effective transcriptome analysis with unique Allium resources successfully associated numerous chromosome markers with unigene information and a high-density A. cepa linkage map. The information on these unigene markers is valuable in genome sequencing and useful trait detection in Allium.

Reactive oxygen species (ROS) are byproducts of normal plant metabolism and their production is elevated under environmental stresses such as drought, extreme temperature, and salinity. Among these, salinity is a worldwide problem that impacts the fertility of arable lands and sustainability of food security, which is getting more attention due to climate change. Halophytes can survive and reproduce in soils containing high concentrations of salt and have developed adaptation mechanisms at physiological, biochemical, and molecular levels including maintenance of ROS metabolism. In this review, we aim to summarize findings related to ROS production, signaling, scavenging, and especially ROS avoidance mechanisms under salt stress. In addition, expressions of antioxidant genes in Arabidopsis thaliana and its close relative, the model halophyte Schrenkiella parvula, are compared. Moreover, time-course expression levels of genes encoding major antioxidant enzymes in the model plant A. thaliana are analyzed with publicly available data to understand rapid responses of antioxidant defense under salt stress. The role of ROS-Ca +2 interaction and involvement of NADPH oxidases in this process are also discussed in the context of the perception and signaling of salt stress.