BackgroundCold tolerance is a key determinant of the geographical distribution range of a plant species and crop production. Cold acclimation can enhance freezing-tolerance of plant species through a period of exposure to low nonfreezing temperatures. As a subtropical evergreen broadleaf plant, oil-tea camellia demonstrates a relatively strong tolerance to freezing temperatures. Moreover, wild oil-tea camellia is an essential genetic resource for the breeding of cultivated oil-tea camellia, one of the four major woody oil crops in the world. The aims of our study are to identify variations in transcriptomes of wild oil-tea camellia from different latitudes and elevations, and discover candidate genes for cold acclimation.ResultsLeaf transcriptomes were obtained of wild oil-tea camellia from different elevations in Lu and Jinggang Mountains, China. Huge amounts of simple sequence repeats (SSRs), single-nucleotide polymorphisms (SNPs) and insertion/deletions (InDels) were identified. Based on SNPs, phylogenetic analysis was performed to detect genetic structure. Wild oil-tea camellia samples were genetically differentiated mainly between latitudes (between Lu and Jinggang Mountains) and then among elevations (within Lu or Jinggang Mountain). Gene expression patterns of wild oil-tea camellia samples were compared among different air temperatures, and differentially expressed genes (DEGs) were discovered. When air temperatures were below 10 °C, gene expression patterns changed dramatically and majority of the DEGs were up-regulated at low temperatures. More DEGs concerned with cold acclimation were detected at 2 °C than at 5 °C, and a putative C-repeat binding factor (CBF) gene was significantly up-regulated only at 2 °C, suggesting a stronger cold stress at 2 °C. We developed a new method for identifying significant functional groups of DEGs. Among the DEGs, transmembrane transporter genes were found to be predominant and many of them encoded transmembrane sugar transporters.ConclusionsOur study provides one of the largest transcriptome dataset in the genus Camellia. Wild oil-tea camellia populations were genetically differentiated between latitudes. It may undergo cold acclimation when air temperatures are below 10 °C. Candidate genes for cold acclimation may be predominantly involved in transmembrane transporter activities.Electronic supplementary materialThe online version of this article (doi:10.1186/s12864-017-3570-4) contains supplementary material, which is available to authorized users.

Picochlorum soloecismus is a halotolerant, fast-growing, and moderate-lipid-producing microalga that is being evaluated as a renewable feedstock for bio-fuel production. Herein, we report on an improved high-quality draft assembly and annotation for the nuclear, chloroplast, and mitochondrial genomes of P. soloecismus DOE 101.

Light intensity (I) is the most dynamic and significant environmental variable affecting photosynthesis (A n), stomatal conductance (g s), transpiration (T r), and water-use efficiency (WUE). Currently, studies characterizing leaf-scale WUE-I responses are rare and key questions have not been answered. In particular, (1) What shape does the response function take? (2) Are there maximum intrinsic (WUE i ; WUE i−max) and instantaneous WUE (WUE inst ; WUE inst−max) at the corresponding saturation irradiances (I i−sat and I inst−sat)? This study developed WUE i-I and WUE inst-I models sharing the same non-asymptotic function with previously published A n-I and g s-I models. Observation-modeling intercomparison was conducted for field-grown plants of soybean (C 3) and grain amaranth (C 4) to assess the robustness of our models versus the non-rectangular hyperbola models (NH models). Both types of models can reproduce WUE-I curves well over light-limited range. However, at light-saturated range, NH models overestimated WUE i−max and WUE inst−max and cannot return I i−sat and I inst−sat due to its asymptotic function. Moreover, NH models cannot describe the downregulation of WUE induced by high light, on which our models described well. The results showed that WUE i and WUE inst increased rapidly within low range of I, driven by uncoupled photosynthesis and stomatal responsiveness. Initial response rapidity of WUE i was higher than WUE inst because the greatest increase of A n and T r occurred at low g s. C 4 species showed higher WUE i−max and WUE inst−max than C 3 species-at similar I i−sat and I inst−sat. Our intercomparison highlighted larger discrepancy between WUE i-I and WUE inst-I responses in C 3 than C 4 species, quantitatively characterizing an

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