Halophytes are plants that can naturally tolerate high concentrations of salt in the soil, and their tolerance to salt stress may occur through various evolutionary and molecular mechanisms. Eutrema salsugineum is a halophytic species in the Brassicaceae that can naturally tolerate multiple types of abiotic stresses that typically limit crop productivity, including extreme salinity and cold. It has been widely used as a laboratorial model for stress biology research in plants. Here, we present the reference genome sequence (241 Mb) of E. salsugineum at 8× coverage sequenced using the traditional Sanger sequencing-based approach with comparison to its close relative Arabidopsis thaliana. The E. salsugineum genome contains 26,531 protein-coding genes and 51.4% of its genome is composed of repetitive sequences that mostly reside in pericentromeric regions. Comparative analyses of the genome structures, protein-coding genes, microRNAs, stress-related pathways, and estimated translation efficiency of proteins between E. salsugineum and A. thaliana suggest that halophyte adaptation to environmental stresses may occur via a global network adjustment of multiple regulatory mechanisms. The E. salsugineum genome provides a resource to identify naturally occurring genetic alterations contributing to the adaptation of halophytic plants to salinity and that might be bioengineered in related crop species.

Endosperm is a filial structure resulting from a second fertilization event in angiosperms. As an absorptive storage organ, endosperm plays an essential role in support of embryo development and seedling germination. The accumulation of carbohydrate and protein storage products in cereal endosperm provides humanity with a major portion of its food, feed, and renewable resources. Little is known regarding the regulatory gene networks controlling endosperm proliferation and differentiation. As a first step toward understanding these networks, we profiled all mRNAs in the maize kernel and endosperm at eight successive stages during the first 12 d after pollination. Analysis of these gene sets identified temporal programs of gene expression, including hundreds of transcriptionfactor genes. We found a close correlation of the sequentially expressed gene sets with distinct cellular and metabolic programs in distinct compartments of the developing endosperm. The results constitute a preliminary atlas of spatiotemporal patterns of endosperm gene expression in support of future efforts for understanding the underlying mechanisms that control seed yield and quality.mRNA localization | time series

ORCID IDs: 0000-0002-3306-5594 (M.X); 0000-0001-6241-6317 (R.Y); 0000-0002-6406-5597 (X.W).In angiosperms, the endosperm provides nutrients for embryogenesis and seed germination and is the primary tissue where gene imprinting occurs. To identify the imprintome of early developing maize (Zea mays) endosperm, we performed highthroughput transcriptome sequencing of whole kernels at 0, 3, and 5 d after pollination (DAP) and endosperms at 7, 10, and 15 DAP, using B73 by Mo17 reciprocal crosses. We observed gradually increased expression of paternal transcripts in 3-and 5-DAP kernels. In 7-DAP endosperm, the majority of the genes tested reached a 2:1 maternal versus paternal ratio, suggesting that paternal genes are nearly fully activated by 7 DAP. A total of 116, 234, and 63 genes exhibiting parent-specific expression were identified at 7, 10, and 15 DAP, respectively. The largest proportion of paternally expressed genes was at 7 DAP, mainly due to the significantly deviated parental allele expression ratio of these genes at this stage, while nearly 80% of the maternally expressed genes (MEGs) were specific to 10 DAP and were primarily attributed to sharply increased expression levels compared with the other stages. Gene ontology enrichment analysis of the imprinted genes suggested that 10-DAP endosperm-specific MEGs are involved in nutrient uptake and allocation and the auxin signaling pathway, coincident with the onset of starch and storage protein accumulation.

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The evolution of a species involves changes in its genome and its transcriptome. Divergence in expression patterns may be more important than divergence in sequences for determining phenotypic changes, particularly among closely related species. We examined the relationships between organ evolution, sequence evolution, and expression evolution in Arabidopsis thaliana, rice (Oryza sativa), and maize (Zea mays). We found correlated divergence of gene sequences and expression patterns, with distinct divergence rates that depend on the organ types in which a gene is expressed. For instance, genes specifically expressed in reproductive organs (i.e., stamen) evolve more quickly than those specifically expressed in vegetative organs (e.g., root). The different rates in organ evolution may be due to different degrees of functional constraint associated with the different physiological functions of plant organs. Additionally, the evolutionary rate of a gene sequence is correlated with the breadth of its expression in terms of the number of tissues, the number of coregulation modules, and the number of species in which the gene is expressed, as well as the number of genes with which it may interact. This linkage supports the hypothesis that constitutively expressed genes may experience higher levels of functional constraint accumulated from multiple tissues than do tissue-specific genes.

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The identification of genetic variations underlying desired phenotypes is one of the main challenges of current livestock genetic research. High-throughput transcriptome sequencing has been recognized as an efficient way to unravel the rich genetic variants across various species. The Lanzhou Fat-Tail sheep is an endangered sheep breed in China with a notable feature of an exaggerated fat tail that also independently occurs in other sheep breeds. However, the genetic mechanism underlying this particular trait has not been fully elucidated yet. In this study, we used RNA-seq on tissue samples (longissimus dorsi muscle, perinephric fat and tail fat) from three sheep breeds with either fat or thin tails and characterized the genetic variation in Lanzhou Fat-Tail sheep with the ultimate goal of identifying the causal genes and genetic networks responsible for the fat tail in this rare sheep breed. In total, 7 122 920 SNPs and 901 518 indels were detected in the nine individual sheep investigated, of which 606 952 SNPs (8.5%) and 77 633 indels (8.6%) overlapped with QTL associated with fat traits in sheep. Furthermore, we detected 26 613 specific SNPs in Lanzhou Fat-Tail sheep and 44 SNPs located in the same genomic position reported in another sheep breed with fat tails. Interestingly, 33 SNPs are selectively distributed on a chromosome 3 region (39.58-40.91 Mb) that was reported as a strong candidate genomic region for fat deposition in tails of sheep. Our research has also suggested that three genes (CREB1, WDR92 and ETAA1) may be associated with fat tail development. In summary, the resultant genetic variants data in this study provide a valuable resource for marker-assisted selection of the trait in Lanzhou Fat-Tail sheep populations.