Transcriptional responses indicate maintenance of photosynthetic proteins as key to the exceptional chilling tolerance of C4 photosynthesis in Miscanthus × giganteus.

Miscanthus × giganteus is exceptional among C4 plants in its ability to acclimate to chilling (≤14 °C) and maintain a high photosynthetic capacity, in sharp contrast to maize, leading to very high productivity even in cool temperate climates. To identify the mechanisms that underlie this acclimation, RNA was isolated from M × giganteus leaves in chilling and nonchilling conditions and hybridized to microarrays developed for its close relative Zea mays. Among 21 000 array probes that yielded robust signals, 723 showed significant expression change under chilling. Approximately half of these were for annotated genes. Thirty genes associated with chloroplast membrane function were all upregulated. Increases in transcripts for the lhcb5 (chlorophyll a/b-binding protein CP26), ndhF (NADH dehydrogenase F, chloroplast), atpA (ATP synthase alpha subunit), psbA (D1), petA (cytochrome f), and lhcb4 (chlorophyll a/b-binding protein CP29), relative to housekeeping genes in M. × giganteus, were confirmed by quantitative reverse-transcription PCR. In contrast, psbo1, lhcb5, psbA, and lhcb4 were all significantly decreased in Z. mays after 14 days of chilling. Western blot analysis of the D1 protein and LHCII type II chlorophyll a/b-binding protein also showed significant increases in M. × giganteus during chilling and significant decreases in Z. mays. Compared to other C4 species, M. × giganteus grown in chilling conditions appears to counteract the loss of photosynthetic proteins and proteins protecting photosystem II typically observed in other species by increasing mRNA levels for their synthesis.

A detailed gene expression study of the Miscanthus genus reveals changes in the transcriptome associated with the rejuvenation of spring rhizomes.

BACKGROUND: The Miscanthus genus of perennial C4 grasses contains promising biofuel crops for temperate climates. However, few genomic resources exist for Miscanthus, which limits understanding of its interesting biology and future genetic improvement. A comprehensive catalog of expressed sequences were generated from a variety of Miscanthus species and tissue types, with an emphasis on characterizing gene expression changes in spring compared to fall rhizomes. RESULTS: Illumina short read sequencing technology was used to produce transcriptome sequences from different tissues and organs during distinct developmental stages for multiple Miscanthus species, including Miscanthus sinensis, Miscanthus sacchariflorus, and their interspecific hybrid Miscanthus × giganteus. More than fifty billion base-pairs of Miscanthus transcript sequence were produced. Overall, 26,230 Sorghum gene models (i.e., ~ 96% of predicted Sorghum genes) had at least five Miscanthus reads mapped to them, suggesting that a large portion of the Miscanthus transcriptome is represented in this dataset. The Miscanthus × giganteus data was used to identify genes preferentially expressed in a single tissue, such as the spring rhizome, using Sorghum bicolor as a reference. Quantitative real-time PCR was used to verify examples of preferential expression predicted via RNA-Seq. Contiguous consensus transcript sequences were assembled for each species and annotated using InterProScan. Sequences from the assembled transcriptome were used to amplify genomic segments from a doubled haploid Miscanthus sinensis and from Miscanthus × giganteus to further disentangle the allelic and paralogous variations in genes. CONCLUSIONS: This large expressed sequence tag collection creates a valuable resource for the study of Miscanthus biology by providing detailed gene sequence information and tissue preferred expression patterns. We have successfully generated a database of transcriptome assemblies and demonstrated its use in the study of genes of interest. Analysis of gene expression profiles revealed biological pathways that exhibit altered regulation in spring compared to fall rhizomes, which are consistent with their different physiological functions. The expression profiles of the subterranean rhizome provides a better understanding of the biological activities of the underground stem structures that are essentials for perenniality and the storage or remobilization of carbon and nutrient resources.

Prospective Randomized Trial Comparing the Safety and Clarity of Water Versus Saline Irrigant in Ureteroscopy.

BACKGROUND: Water irrigant is discouraged in ureteroscopy due to risks demonstrated in more invasive endoscopic procedures. However, water is not well studied in ureteroscopy and may provide better visualization than standard saline. OBJECTIVE: To determine whether water irrigant increases the risk of hyponatremia compared with saline and provides better visualization in ureteroscopy. DESIGN, SETTING, AND PARTICIPANTS: A randomized, prospective, double-blinded trial was conducted. In 2017, eligible adult ureteroscopy patients at a university hospital were recruited for the study. INTERVENTION: Participants randomized to water or saline irrigant in ureteroscopy. OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS: Serum sodium and osmolality, body temperature, subjective surgeon visualization, and objective turbidity clarity were analyzed. Chi-square or Fisher's exact tests for categorical variables and analysis of variance test for continuous variables were performed. RESULTS AND LIMITATIONS: A total of 121 individuals (mean age 57 ± 15 yr) underwent ureteroscopy (mean time 35 ± 18 min) with a mean irrigation volume of 839 ± 608 ml. For the 101 (83%) patients who had nephrolithiasis, the mean number of stones was 2 ± 1 and the mean stone burden was 13 ± 7 mm. There were no significant differences in demographic, clinical, and intraoperative variables between water and saline groups, except for a higher body mass index in the saline group (p = 0.01). There was no significant difference between groups in the incidence of hyponatremia, hypo-osmolality, or hypothermia. The median surgeon visualization score was significantly higher using water (p < 0.01). The mean turbidity was significantly lower with water (p = 0.02). Limitations were not objectively assessing hemolysis or fluid absorption. CONCLUSIONS: Water irrigant does not increase the incidence of hyponatremia in uncomplicated ureteroscopy and provides clearer visualization than saline. PATIENT SUMMARY: We compared safety and clarity of water and saline irrigation, which aid surgeon visualization, in ureteroscopy, which can treat kidney stones. We found that water irrigant does not reduce blood sodium levels significantly compared with saline in ureteroscopy and provides better visualization.

Toward cool C(4) crops.

C(4) photosynthesis under optimal conditions enables higher-efficiency use of light, water, and nitrogen than the C(3) form used by many crops. It is associated with the most productive terrestrial plants and crops but is largely limited to the tropics and subtropics. It has been argued that the C(4) photosynthetic apparatus is inherently limited to warm environments. A small group of C(4) species appear to have overcome this, and in contrast to the major C(4) crop, maize, these species are able to acclimate their photosynthetic apparatus to chilling conditions. This review explores the mechanisms underlying this difference as well as the potential of introducing these changes into maize and other warm-climate C(4) crops.

Genome of the long-living sacred lotus (Nelumbo nucifera Gaertn.).

BACKGROUND: Sacred lotus is a basal eudicot with agricultural, medicinal, cultural and religious importance. It was domesticated in Asia about 7,000 years ago, and cultivated for its rhizomes and seeds as a food crop. It is particularly noted for its 1,300-year seed longevity and exceptional water repellency, known as the lotus effect. The latter property is due to the nanoscopic closely packed protuberances of its self-cleaning leaf surface, which have been adapted for the manufacture of a self-cleaning industrial paint, Lotusan. RESULTS: The genome of the China Antique variety of the sacred lotus was sequenced with Illumina and 454 technologies, at respective depths of 101× and 5.2×. The final assembly has a contig N50 of 38.8 kbp and a scaffold N50 of 3.4 Mbp, and covers 86.5% of the estimated 929 Mbp total genome size. The genome notably lacks the paleo-triplication observed in other eudicots, but reveals a lineage-specific duplication. The genome has evidence of slow evolution, with a 30% slower nucleotide mutation rate than observed in grape. Comparisons of the available sequenced genomes suggest a minimum gene set for vascular plants of 4,223 genes. Strikingly, the sacred lotus has 16 COG2132 multi-copper oxidase family proteins with root-specific expression; these are involved in root meristem phosphate starvation, reflecting adaptation to limited nutrient availability in an aquatic environment. CONCLUSIONS: The slow nucleotide substitution rate makes the sacred lotus a better resource than the current standard, grape, for reconstructing the pan-eudicot genome, and should therefore accelerate comparative analysis between eudicots and monocots.