Abstract Background The deep-sea may be regarded as a hostile living environment, due to low temperature, high hydrostatic pressure, and limited food and light. Isopods, a species-rich group of crustaceans, are widely distributed across different environments including the deep sea and as such are a useful model for studying adaptation, migration, and speciation. Similar to other deep-sea organisms, giant isopods have larger body size than their shallow water relatives and have large stomachs and fat bodies presumably to store organic reserves. In order to shed light on the genetic basis of these large crustaceans adapting to the oligotrophic environment of deep-sea, the high-quality genome of a deep-sea giant isopod Bathynomus jamesi was sequenced and assembled. Results B. jamesi has a large genome of 5.89 Gb, representing the largest sequenced crustacean genome to date. Its large genome size is mainly attributable to the remarkable proliferation of transposable elements (84%), which may enable high genome plasticity for adaptive evolution. Unlike its relatives with small body size, B. jamesi has expanded gene families related to pathways of thyroid and insulin hormone signaling that potentially contribute to its large body size. Transcriptomic analysis showed that some expanded gene families related to glycolysis and vesicular transport were specifically expressed in its digestive organs. In addition, comparative genomics and gene expression analyses in six tissues suggested that B. jamesi has inefficient lipid degradation, low basal metabolic rate, and bulk food storage, suggesting giant isopods adopt a more efficient mechanism of nutrient absorption, storage, and utilization to provide sustained energy supply for their large body size. Conclusions Taken together, the giant isopod genome may provide a valuable resource for understanding body size evolution and adaptation mechanisms of macrobenthic organisms to deep-sea environments.
Waterlogging caused by short and severe, or prolonged precipitation can be attributed to global warming.Pumpkin plants are drought-tolerant but not tolerate to waterlogging stress.Under frequent rain and waterlogging conditions, the production of pumpkins is of lower quality, sometimes rotten, and harvest failure occurs in severe cases.Therefore, it is of great significance to assess the waterlogging tolerance mechanism of pumpkin plants.In this study, 10 novel pumpkin varieties from Baimi series were used.The waterlogging tolerance level of pumpkin plants was evaluated by measuring waterlogging tolerance coefficient of biomass and physiological indices using waterlogging stress simulation method.The criteria to evaluate the waterlogging tolerance capacities of pumpkin plants were also explored.Using principal component and membership function analysis, waterlogging tolerance levels of the pumpkin varieties were ranked as follows: Baimi No. 10> Baimi No. 5> Baimi No. 1> Baimi No. 2> Baimi No. 3> Baimi No. 7> Baimi No. 9> Baimi No. 6> Baimi No. 4> Baimi No. 8. Based on the results, Baimi No. 10 was identified with strong waterlogging tolerance and Baimi No. 8 with weak waterlogging tolerance.The responses of malondialdehyde (MDA), proline, key enzymes responsible for anaerobic respiration, and antioxidant enzymes to waterlogging stress were studied in pumpkin plants.The relative expression levels of related genes were determined using real-time fluorescence quantitative PCR technique.The aim of our study was to assess the waterlogging tolerance mechanism of pumpkin plants, thus laying a theoretical foundation for breeding waterlogging-tolerant varieties in the future.After flooding stress treatment, the antioxidant enzyme activities, contents of proline and alcohol dehydrogenases of BaimiNo. 10 and Baimi No. 8 displayed an increase followed by a decrease.All indices of Baimi No. 10 were higher than Baimi No. 8. MDA contents gradually increased, with the content being higher in Baimi No. 8 than Baimi No. 10.The activities of pyruvate decarboxylases (PDCs) in Baimi No. 8 and Baimi No. 10 exhibited a decrease initially, followed by an increase, and then a decrease again.The PDC activity in Baimi No. 8 was generally higher
Based on the data obtained from 24 stations in autumn 2000 and spring 2001, the secondary production of macrobenthos in the southern Yellow Sea was calculated with Brey's (1990) empirical formula. The results showed that the mean abundance in autumn (2000) was 154.2 ind./m^2, subequal to that in spring (2001), 147.8 ind./m2; the mean biomass in AFDW (ash - free dry weight) in autumn was 6.92 g/m^2, much more than that in spring (2.81 g/m^2 ) ; and the mean annual secondary production in the study area was 4.98 g (AFDW) m^(-2) a^(-1). There were two centers of high production, as well as biomass, in southwest and southeast of the study area. The biomass and production of macrobenthos were affected by water temperature, as the two higher value centers of biomass and production distributed outside of the Yellow Sea Cold Water Mass. The average annual macrobenthic P/B ratio (ratio of production to biomass) of the southern Yellow Sea was 1.10 a^(-1). Comparing with the results[production = 6.49 g (AFDW) m(-2) a^(-1); P/B = 0.82 a^(-1)] from the Bohai Bay, it was confirmed that the community production decreased with the increasing of water depth, and P/B ratio increased with the rising of water temperature. Fig 2, Tab 2, Ref 31
FIGURE 2. Diactins and acanthophores of Lophophysema eversa sp. nov. A–M, Diactins: A–E, general appearance of whole diactins. F–I, magnified ends of different types of diactins. J–M, magnified middle parts of different types of diactins. N–R, acanthophores: N, diactins, O–P, stauractins, Q, pentactins, R, hexactins.
Exiguobacterium sp. strain JLM-2 is a thermophilic bacterium isolated from deep-sea ferromanganese (FeMn) nodules. The estimated genome of this strain is 2.9 Mb, with a G+C content of 48.32%. It has a novel circular 15,570-bp plasmid. The draft genome sequence may provide useful information about Mn-microbe interactions and the genetic basis for tolerance to environment stresses.
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