Chromosome-level genome assembly of a triploid poplar Populus alba 'Berolinensis'.

Many recent studies have provided significant insights into polyploid breeding, but limited research has been carried out on trees. The genomic information needed to understand growth and response to abiotic stress in polyploidy trees is largely unknown, but has become critical due to the threats to forests imposed by climate change. Populus alba 'Berolinensis,' also known "Yinzhong poplar," is a triploid poplar from northeast China. This hybrid triploid poplar is widely used as a landscape ornamental and in urban forestry owing to its adaptation to adverse environments and faster growth than its parental diploid. It is an artificially synthesized male allotriploid hybrid, with three haploid genomes of P. alba 'Berolinensis' originating from different poplar species, so it is attractive for studying polyploidy genomic mechanisms in heterosis. In this study, we focused on the allelic genomic interactions in P. alba 'Berolinensis,' and generated a high-quality chromosome-level genome assembly consisting of 19 allelic chromosomes. Its three haploid chromosome sets are polymorphic with an average of 25.73 nucleotide polymorphism sites per kilobase. We found that some stress-related genes such as RD22 and LEA7 exhibited sequence differences between different haploid genomes. The genome assembly has been deposited in our polyploid genome online analysis website TreeGenomes (https://www.treegenomes.com). These polyploid genome-related resources will provide a critical foundation for the molecular breeding of P. alba 'Berolinensis' and help us uncover the allopolyploidization effects of heterosis and abiotic stress resistance and traits of polyploidy species in the future.

Mucilaginibacter gilvus sp. nov., isolated from Antarctic soil.

A Gram-stain-negative, aerobic, non-motile, rod-shaped, cold-tolerant bacterium, designated F01003T, was isolated from soil sampled near Happiness Bay on the west coast of Antarctica. Strain F01003T was found to grow at 4-30 °C (optimum, 25 °C), pH 5.5-8.0 (pH 6.5-7.0) and in the presence of 0-1 % NaCl (0 %, w/v). Cells were oxidase-positive and catalase-positive. Strain F01003T contained menaquinone 7 (MK-7) as the predominant respiratory quinone. The main cellular fatty acids included summed feature 3 (C16 : 1ω6c and/or C16 : 1ω7c) and iso-C15 : 0. Phosphatidylethanolamine and an unidentified aminolipid were identified as the major polar lipids. The DNA G+C content of strain F01003T was 44.8 mol%. Phylogenetic analysis of the nearly full-length 16S rRNA gene sequence revealed that strain F01003T was most closely related to the genus Mucilaginibacter and exhibited the highest sequence similarity to Mucilaginibacter phyllosphaerae LMG 29118T (97.3 %). On the basis of the evidence presented in this polyphasic taxonomic study, strain F01003T is considered to represent a novel species of the genus Mucilaginibacter, for which the name Mucilaginibactergilvus sp. nov. is proposed. The type strain is F01003T (=KCTC 62991T=CCTCC AB 2019023T).

Pedobacter changchengzhani sp. nov., isolated from soil of Antarctica.

A Gram-negative, aerobic, non-motile, pink and rod-shaped bacterium, designated E01020T, was isolated from soil collected from the Chinese Great Wall Station, Antarctica. Comparative analysis of 16S rRNA gene sequences revealed that strain E01020T is a member of the genus Pedobacter, related to Pedobacter alluvionis DSM 19624T (96.8% similarity), Pedobacter agri JCM 15120T (96.5% similarity) and Pedobacter chinensis JDX94T (96.3% similarity). The dDDH values and ANI values of strain E01020T with closely related strains indicate that it can be distinguished from them as a novel species. The DNA G+C content was determined to be 35.2 mol%. The growth of strain E01020T was observed at 4-25 °C (optimal 20 °C), in the presence of 0-1% NaCl (w/v, optimal 0%) and at pH 6.0-8.0 (optimal pH 7.0). Strain E01020T was found to contained menaquinon-7 (MK-7) as only respiratory quinone, iso-C15:0, iso-C17:0 3-OH and Summed feature 3 (C16:1ω6c and/or C16:1ω7c) as major fatty acids. The major polar lipids were phosphatidylethanolamine, one unidentified lipid and two unidentified aminolipids. On the basis of the results of the phylogenetic and phenotypic analyses, it was suggested that strain E01020T represents a novel species of the genus Pedobacter, for which the name Pedobacter changchengzhani sp. nov. is proposed. The type strain is E01020T (= KCTC 62990T = MCCC 1H00357T).