Acyl carrier protein OsMTACP2 confers rice cold tolerance at the booting stage.

Low temperatures occurring at the booting stage in rice (Oryza sativa L.) often result in yield loss by impeding male reproductive development. However, the underlying mechanisms by which rice responds to cold at this stage remain largely unknown. Here, we identified MITOCHONDRIAL ACYL CARRIER PROTEIN 2 (OsMTACP2), the encoded protein of which mediates lipid metabolism involved in the cold response at the booting stage. Loss of OsMTACP2 function compromised cold tolerance, hindering anther cuticle and pollen wall development, resulting in abnormal anther morphology, lower pollen fertility, and seed setting. OsMTACP2 was highly expressed in tapetal cells and microspores during anther development, with the encoded protein localizing to both mitochondria and the cytoplasm. Comparative transcriptomic analysis revealed differential expression of genes related to lipid metabolism between the wild type and the Osmtacp2-1 mutant in response to cold. Through a lipidomic analysis, we demonstrated that wax esters, which are the primary lipid components of the anther cuticle and pollen walls, function as cold-responsive lipids. Their levels increased dramatically in the wild type but not in Osmtacp2-1 when exposed to cold. Additionally, mutants of two cold-induced genes of wax ester biosynthesis, ECERIFERUM1 and WAX CRYSTAL-SPARSE LEAF2, showed decreased cold tolerance. These results suggest that OsMTACP2-mediated wax ester biosynthesis is essential for cold tolerance in rice at the booting stage.

DEAD-BOX RNA HELICASE 27 regulates microRNA biogenesis, zygote division, and stem cell homeostasis.

After double fertilization, zygotic embryogenesis initiates a new life cycle, and stem cell homeostasis in the shoot apical meristem (SAM) and root apical meristem (RAM) allows plants to produce new tissues and organs continuously. Here, we report that mutations in DEAD-BOX RNA HELICASE 27 (RH27) affect zygote division and stem cell homeostasis in Arabidopsis (Arabidopsis thaliana). The strong mutant allele rh27-1 caused a zygote-lethal phenotype, while the weak mutant allele rh27-2 led to minor defects in embryogenesis and severely compromised stem cell homeostasis in the SAM and RAM. RH27 is expressed in embryos from the zygote stage, and in both the SAM and RAM, and RH27 is a nucleus-localized protein. The expression levels of genes related to stem cell homeostasis were elevated in rh27-2 plants, alongside down-regulation of their regulatory microRNAs (miRNAs). Further analyses of rh27-2 plants revealed reduced levels of a large subset of miRNAs and their pri-miRNAs in shoot apices and root tips. In addition, biochemical studies showed that RH27 associates with pri-miRNAs and interacts with miRNA-biogenesis components, including DAWDLE, HYPONASTIC LEAVES 1, and SERRATE. Therefore, we propose that RH27 is a component of the microprocessor complex and is critical for zygote division and stem cell homeostasis.

Streptomyces plumbidurans sp. nov., a Pb2+-tolerant actinomycete.

A novel actinobacterium, designated KC 17012T, was isolated from lead zinc tailings collected from Lanping, Yunnan, PR China. Comparative 16S rRNA gene sequencing showed that KC 17012T belonged to the genus Streptomyces and was most closely related to the type strains of Streptomyces neyagawaensis (98.34%), Streptomyces panaciradicis (98.34%) and Streptomyces heilongjiangensis (98.27%). Phylogenetic tree analysis revealed strain KC 17012T formed a distinct clade. The genome size was 8.64 Mbp with a DNA G+C content of 70.8%. Digital DNA-DNA hybridization and average nucleotide identity values between the genome sequence of strain KC 17012T and those of S. neyagawaensis JCM 4796T (25.3 and 81.5 %) and S. panaciradicis NBRC 109811T (30.1 and 85.7 %) were below the thresholds of 70 and 96% for prokaryotic conspecific assignation. The strain formed long straight aerial hyphae which generated regular short rod spores with spiny surfaces. Growth occurred at 10-45 °C, pH 6-8 and with 0-9 % NaCl (w/v). Strain KC 17012T contained ll-diaminopimelic acid and the major whole-cell hydrolysates included glucose, mannose and ribose. The menaquinones were MK-9(H4), MK-9(H6) and MK-9(H8). The major cellular fatty acids were iso-C15 : 0, anteiso-C15 : 0, iso-C16 : 0 and anteiso-C17 : 0. The polar lipid profile consisted of diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylglycerol, phosphatidylinositol, phosphatidylinositol mannoside, one unidentified lipid and one unidentified phospholipid. On the basis of the results of a polyphasic taxonomic study, it is concluded that KC 17012T represents a novel species of the genus Streptomyces, for which the name Streptomyces plumbidurans sp. nov., is proposed. The type strain is KC 17012T (CGMCC 4.7704T=JCM 35204T).

Siccirubricoccus soli sp. nov., a novel bacterial species isolated from Jiaozi Mountain soil.

An isolate of Gram-stain-negative and strictly aerobic bacterium, designated KC 17139T, was isolated from Jiaozi Mountain sample in Yunnan, China. Cells were non-motile cocci to oval, catalase-positive and oxidase-positive. Growth occurred at 0-7% NaCl (w/v; optimum, 0%), pH 6.0-8.0 (optimum, pH 7.0) and 15-45 °C (optimum, 28-37 °C). The polar lipids were diphosphatidylglycerol (DPG), phosphatidylethanolamine (PE), phosphatidylglycerol (PG), phosphatidylcholine (PC) and four unidentified aminolipids (UALs). Strain KC 17139T contained summed feature 8 (comprising C18:1 ω7c and/or C18:1 ω6c), C18:1 2OH and C16:0 as major cellular fatty acids (> 5%) and ubiquinone-10 as the sole isoprenoid quinone. The 16S rRNA gene sequence analysis indicated that strain KC 17139T shared highest similarities with Siccirubricoccus phaeus 1-3T (96.7%) and Siccirubricoccus deserti SYSU D8009T (95.0%). Strain KC 17139T clustered with the two Siccirubricoccus type strains, but formed a separate branch in both 16S rRNA gene and genome-scale phylogenetic dendrograms. The genomic DNA G + C content of strain KC 17139T was 71.2%. Genomic comparisons between strain KC 17139T and its close relatives showed the highest digital DNA-DNA hybridisation to S. phaeus (35.5%), highest average nucleotide identity to S. phaeus (88.2%), indicating that strain KC 17139T represents a novel species. On the basis of results of phenotypic, chemotaxonomic and molecular analysis, we report a new bacterium strain KC 17139T belonged to genus Siccirubricoccus, for which the name Siccirubricoccus soli sp. nov. is proposed. The type strain is KC 17139T (= CGMCC 1.18756T = JCM 35132T).

CLE peptides: critical regulators for stem cell maintenance in plants.

MAIN CONCLUSION: Plant CLE peptides, which regulate stem cell maintenance in shoot and root meristems and in vascular bundles through LRR family receptor kinases, are novel, complex, and to some extent conserved. Over the past two decades, peptide ligands of the CLAVATA3 (CLV3) /Embryo Surrounding Region (CLE) family have been recognized as critical short- and long-distance communication signals in plants, especially for stem cell homeostasis, cell fate determination and physiological responses. Stem cells located at the shoot apical meristem (SAM), the root apical meristem (RAM) and the procambium divide and differentiate into specialized cells that form a variety of tissues such as epidermis, ground tissues, xylem and phloem. In the SAM of Arabidopsis (Arabidopsis thaliana), the CLV3 peptide restricts the number of stem cells via leucine-rich repeat (LRR)-type receptor kinases. In the RAM, root-active CLE peptides are critical negative regulators, while ROOT GROWTH FACTOR (RGF) peptides are positive regulators in stem cell maintenance. Among those root-active CLE peptides, CLE25 promotes, while CLE45 inhibits phloem differentiation. In vascular bundles, TRACHEARY ELEMENT DIFFERENTIATION INHIBITORY FACTOR (TDIF)/CLE41/CLE44 promotes procambium cell division, and prevents xylem differentiation. Orthologs of CLV3 have been identified in liverwort (Marchantia polymorpha), tomato (Solanum lycopersicum), rice (Oryza sativa), maize (Zea mays) and lotus (Lotus japonicas), suggesting that CLV3 is an evolutionarily conserved signal in stem cell maintenance. However, functional characterization of endogenous CLE peptides and corresponding receptor kinases, and the downstream signal transduction has been challenging due to their genome-wide redundancies and rapid evolution.

ZYGOTE-ARREST 3 that encodes the tRNA ligase is essential for zygote division in Arabidopsis.

In sexual organisms, division of the zygote initiates a new life cycle. Although several genes involved in zygote division are known in plants, how the zygote is activated to start embryogenesis has remained elusive. Here, we showed that a mutation in ZYGOTE-ARREST 3 (ZYG3) in Arabidopsis led to a tight zygote-lethal phenotype. Map-based cloning revealed that ZYG3 encodes the transfer RNA (tRNA) ligase AtRNL, which is a single-copy gene in the Arabidopsis genome. Expression analyses showed that AtRNL is expressed throughout zygotic embryogenesis, and in meristematic tissues. Using pAtRNL::cAtRNL-sYFP-complemented zyg3/zyg3 plants, we showed that AtRNL is localized exclusively in the cytoplasm, suggesting that tRNA splicing occurs primarily in the cytoplasm. Analyses using partially rescued embryos showed that mutation in AtRNL compromised splicing of intron-containing tRNA. Mutations of two tRNA endonuclease genes, SEN1 and SEN2, also led to a zygote-lethal phenotype. These results together suggest that tRNA splicing is critical for initiating zygote division in Arabidopsis.

[Impacts of atovastatin and tinidazole on cardiac muscle inflammation factors of tumor necrosis factor-α, interleukin-1 and metalloproteinase-2 of experimental rabbits with atherosclerosis and periodontitis].

OBJECTIVE: To explore the effects of atovastatin and tinidazole on atherosclerosis and the levels of tumor necrosis factor-α (TNF-α), interleukin-1 (IL-1) and matrix metalloproteinase-2 (MMP-2) in periodontitis. METHODS: A total of 48 male New Zealand white rabbits were randomly divided into 4 groups (n = 12 each): control group (A), atovastatin group (B), tinidazole group (C) and combination group (D, atovastatin + tinidazole). All groups received interventions according to the experiment design. During Week 1-4, mandibular first premolars were used to establish periodontitis model. For Week 1, adaptive feeding was provided with 50% normal diet + 50% high-fat diet. Then a full high fat-diet was used to establish atherosclerosis model. During Week 16-20, experimental drug intervention was administered twice weekly: group A received the same volume of saline, group B atorvastatin tablets 1.5 mg/kg, group C tinidazole tablets 150 mg/kg and group D atorvastatin tablets 1.5 mg/kg + tinidazole tablets 150 mg/kg. At the end of 20-week intervention, the animals were sacrificed to take vascular and heart tissue samples. Immunohistochemistry and fluorescent polymerase chain reaction (PCR) were employed for quantitative determinations. RESULTS: The positive areas of MMP-2 expression in groups B, C and D were smaller than that of group A respectively (35% ± 17%, 69% ± 5%, 30% ± 7% vs 86% ± 9%, all P < 0.05). And the PCR results showed the levels of TNF-α and IL-1 in group D was the lowest of four groups (all P < 0.05). CONCLUSION: Atovastatin and tinidazole can reduce the expression levels of TNF-α, IL-1 and MMP-2 in the rabbits with atherosclerosis and periodontitis respectively. And the combination of both drugs may achieve a better efficacy.