The content of walnut metabolites is related to its nutritive value and physiological characteristics, however, comprehensive information concerning the metabolome of walnut kernels is limited. In this study we analyzed the metabolites of walnut kernels at five developmental stages from filling to ripening using GC-MS-based untargeted metabolomics; of a total 252 peaks identified, 85 metabolites were positively identified. Further statistical analysis revealed that these 85 metabolites covered different types of metabolism pathways. PCA scores revealed that the metabolic compositions of the embryo are different at each stage, while the metabolic composition of the endotesta could not be significantly separated into distinct groups. Additionally, 7225 metabolite-metabolite correlations were detected in walnut kernel by a Pearson correlation coefficient approach; during screening of the calculated correlations, 463 and 1047 were determined to be significant with r2≥0.49 and had a false discovery rate (FDR) ≤0.05 in endotesta and embryo, respectively. This work provides the first comprehensive metabolomic study of walnut kernels and reveals that most of the carbohydrate and protein-derived carbon was transferred into other compounds, such as fatty acids, during the maturation of walnuts, which may potentially provide the basis for further studies on walnut kernel metabolism.

Fruit ripening is a developmental process regulated by a complex network of endogenous and exogenous cues. Sea buckthorn is an excellent material for fruit ripening studies due to its dramatic ripening process and high contents of nutritional and anti-oxidant compounds in berries. Here, the whole transcriptome of sea buckthorn fruit at three development stages were analysed using multiple high-throughput sequencings. We assembled and annotated 9,008 long non-coding RNAs (lncRNAs) in sea buckthorn fruits, and identified 118 differentially expressed lncRNAs (DE-lncRNAs) and 32 differentially expressed microRNAs in fruit developmental process. In addition, we predicted 1,061 cis-regulated and 782 trans-regulated targets of DE-lncRNAs, and these DE-lncRNAs are specifically enriched in the biosynthesis of ascorbic acid, carotenoids and flavonoids. Moreover, the silencing of two lncRNAs (LNC1 and LNC2) in vivo and expression analysis revealed that LNC1 and LNC2 can act as endogenous target mimics of miR156a and miR828a to reduce SPL9 and induce MYB114 expression, respectively, which lead to increased and decreased anthocyanin content as revealed by high-performance liquid chromatography analysis. Our results present the first global functional analysis of lncRNA in sea buckthorn and provide two essential regulators of anthocyanin biosynthesis, which provides new insights into the regulation of fruit quality.

Background: As one of the fastest-growing lignocellulose-abundant plants on Earth, bamboos can reach their final height quickly due to the expansion of individual internodes already present in the buds; however, the molecular processes underlying this phenomenon remain unclear. Moso bamboo (Phyllostachys heterocyclacv. Pubescens) internodes from four different developmental stages and three different internodes within the same stage were used in our study to investigate the molecular processes at the transcriptome and post-transcriptome level.Results: Our anatomical observations indicated the development of culms was dominated by cell division in the initial stages and by cell elongation in the middle and late stages. The four major endogenous hormones appeared to actively promote culm development. Using next-generation sequencing-based RNA-Seq, mRNA and microRNA expression profiling technology, we produced a transcriptome and post-transcriptome in possession of a large fraction of annotated Moso bamboo genes, and provided a molecular basis underlying the phenomenon of sequentially elongated internodes from the base to the top. Several key pathways such as environmental adaptation, signal transduction, translation, transport and many metabolisms were identified as involved in the rapid elongation of bamboo culms.Conclusions: This is the first report on the temporal and spatial transcriptome and gene expression and microRNA profiling in a developing bamboo culms. In addition to gaining more insight into the unique growth characteristics of bamboo, we provide a good case study to analyze gene, microRNA expression and profiling of non-model plant species using high-throughput short-read sequencing. Also, we demonstrate that the integrated analysis of our multi-omics data, including transcriptome, post-transcriptome, proteome, yield more complete representations and additional biological insights, especially the complex dynamic processes occurring in Moso bamboo culms.

Although, the Abaso section is widely accepted as an independent section, the taxonomic status of Populus mexicana (section Abaso) has not yet been resolved due to the limited availability markers and/or the lack of P. mexicana specimens in previous studies. Thirty-one poplar species that represent six sections of the Populus genus were sampled, and 23 single-copy nuclear DNA and 34 chloroplast fragments were sequenced. The present study obtained two updated phylogenies of Populus. We found that monophyly of the genus Populus is strongly supported by nuclear and plastid gene, which is consistent with previous studies. P. mexicana, diverged first in the nuclear DNA tree, which occupied the basal position, implying that the section Abaso may be the most ancestral lineage in extant populous species. Given that the short branches and low statistical support for the divergence of sections Abaso and Turanga, this observation probably indicated that a rapid radiation evolution following the early split of the genus Populus. In the plastid tree, P. mexicana clustered with modern-day species of section Tacamahaca in the plastid tree. Based on cytoplasmic and single-copy nuclear marker sequences, we hypothesized that chloroplast capture resulted in the inconsistent position of P. mexicana between the phylogenetic trees. Given the first unequivocal records of poplar fossils from the Eocene with similar leaf morphology to the extant P. mexicana and the phylogenetic positions of P. mexicana in our study, we support the hypothesis that the Populus genus originated in North America, which will provide new insights to the development of the origin of Populus species.