Partial replacement of soybean meal with Methylobacterium extorquens single‐cell protein in feeds for rainbow trout (Oncorhynchus mykiss Walbaum)

A feeding trial was conducted with juvenile rainbow trout (15–16 g initial weight) to assess the effects of including single‐cell protein (SCP) produced from Methylobacterium extorquens in trout feeds. Three isonitrogenous and isoenergetic diets were produced: a control diet and two experimental diets containing 5% or 10% bacterial protein meal replacing soybean meal. Triplicate tanks, each containing 35 fish, were fed each diet to apparent satiation in a constant‐temperature (15°C), flow‐through tank system for 12 weeks. No statistically significant differences in final fish weight or other fish growth parameters were observed. Similarly, feed efficiency parameters showed no significant differences among groups. Nutrient retention indices (protein, fat, energy) were relatively high and similar among fish in each dietary treatment group, as were whole body proximate compositions. Fish survival was high, with a small but statistically significant increase for the 10% SCP diet. Overall, results demonstrate that SCP from M. extorquens is a safe and effective alternative protein for rainbow trout diets at the low inclusion levels tested. Slightly lower weight gain in fish fed the 10% SCP diet was largely due to lower feed intake, suggesting that adding palatability‐enhancing ingredients to feeds may allow higher levels of M. extorquens SCP to be used without compromising fish growth.     

嗜酸乳杆菌高密度发酵研究进展

嗜酸乳杆菌是一种具有重要商业价值的益生菌,嗜酸乳杆菌的高密度发酵技术对于该菌的工业化生产有重要应用价值。本文对嗜酸乳杆菌的营养需求、冷冻环境适应策略以及高密度发酵探索等方面的研究进行综述,旨在为嗜酸乳杆菌的生产提供理论参考。     

Viral infection‐induced endoplasmic reticulum stress and a membrane‐associated transcription factor NbNAC089 are involved in resistance to virus in Nicotiana benthamiana

Endoplasmic reticulum (ER) stress may induce two cell defence pathways, the unfolded protein response (UPR) or programmed cell death (PCD) upon unmitigated stress. This study confirmed that viral infection could induce ER stress through changing ER morphology and up‐regulating ER stress‐related genes, including NbNAC089. AtNAC089 serves as an ER stress sensor to regulate PCD in Arabidopsis. In this study, Nicotiana benthamiana NbNAC089 was identified. The gene encoded a 409 amino acid protein with a putative transmembrane domain near the C‐terminus and a NAC domain at the N‐terminus. NbNAC089 was localized to the ER membranes, and a truncated form of NbNAC089, lacking the transmembrane domain, was localized to the nucleus. Meanwhile, the full length of NbNAC089 was activated and cleaved in response to viral infection. The results suggest that the native protein may be translocated to the nucleus by release from the membrane during viral infection. Knock‐down of NbNAC089 in N. benthamiana increased susceptibility to Tobacco mosaic virus or Cucumber mosaic virus, and, in addition, promoted up‐regulation of UPR genes but impaired up‐regulation of PCD genes. These results show that NbNAC089 is a negative regulator of UPR and a positive regulator of PCD, and plays a role in the process of viral infection.     

蓝光对龙眼细胞培养及类黄酮代谢的影响

采用搅拌式生物反应器放大培养龙眼悬浮细胞,探讨蓝光对龙眼细胞生长及类黄酮积累的影响。基于已建立并优化的龙眼细胞悬浮培养体系,首先研究龙眼细胞在黑暗和蓝光的培养过程中,细胞生长量、类黄酮含量、细胞活力、培养液的底物消耗量等的变化情况。结果发现:龙眼细胞培养9 d后,蓝光的细胞干重比黑暗增长了0.28 g/L,类黄酮含量增长了0.77 mg/g。细胞培养前期蓝光的培养液蔗糖消耗速度慢于黑暗培养,此后蔗糖含量均稳定在2 g/L。培养过程中,蓝光培养的还原糖含量均高于黑暗培养,蓝光的磷酸盐的消耗量基本大于黑暗培养。其次,通过qPCR技术分析光信号转录因子DlHY5、调控基因DlPAP1及类黄酮途径合成基因DlCHS的表达差异。结果表明蓝光可能通过光信号转录因子DlHY5调控基因DlPAP1的表达,进而调控龙眼类黄酮代谢途径合成基因DlCHS的表达,从而导致类黄酮的积累。     

小果野蕉（Musa acuminate Colla）花粉母细胞减数分裂过程 异常的细胞学观察

香蕉是重要的热带水果,由于雄性不育、单性结实等原因导致其杂交育种困难。小果野蕉（Musa acuminate Colla）是现代香蕉栽培种的祖先之一,在理论研究和应用中有非常重要的地位。前期研究发现小果野蕉存在部分可育 花粉,但导致花粉活力下降的原因未知。为了探求导致小果野蕉花粉活力降低的细胞学原因,本研究通过亚历山大红 染色法对小果野蕉花粉活力进行检测,通过卡宝品红染色对小果野蕉花粉母细胞减数分裂阶段和小孢子发育阶段进行 观察。结果表明：小果野蕉花粉活力为 84.33%;小孢子发育阶段未见明显异常;正常四分体比例为 81.3%;花粉母细 胞减数分裂过程终变期、中期Ⅰ、后期Ⅰ、中期Ⅱ、后期Ⅱ均存在异常,比例分别为 8.8%、8.5%、7.6%、10.6%、12.1%。 因此,可能是部分花粉母细胞减数分裂异常导致小果野蕉花粉活力的降低。     

Relationships among the chalkiness,kernel size and endosperm cell morphology of rice kernels at different spikelet positions within a panicle

The occurrence of chalky kernels in rice is causally related to kernel size and endosperm morphology. This study aimed to investigate the occurrence of chalky kernels by analyzing kernel size, and the number and area of endosperm cells. Spikelets were sampled from upper and middle primary branches and lower secondary branches in a panicle, and divided into four categories: upper, middle, and lower perfect (PF) kernels and lower milky-white (MW) kernels. On the lower secondary branches, there was a higher percentage of chalky kernels, with smaller kernel lengths, widths and thicknesses, than the kernels on the upper and middle primary branches. MW kernels were smaller in size than PF kernels even on the same lower secondary branches. Regardless of grain appearance quality traits, the total areas of endosperm cross sections in lower kernels were significantly smaller than in upper kernels owing to the decreased cell area, and there was a significant negative correlation between the number of cells and average cell area. When the numbers and the areas of cells were analyzed using angular 30° intervals from the line connecting the center point and the dorsal vascular bundle, the MW kernels had significantly less cells than PF kernels near the ventral side at 120–180°. Thus, the decrease in the number of cells near the ventral side was a main causal factor in the decrease in MW kernel widths compared with PF kernel widths, and this suggested that cell division in MW kernels was inhibited at the early grain-filling stage.     

脂肪间充质干细胞生物学特性及分泌功能研究

脂肪间充质干细胞(ADSCs)来源广泛,取材方便,易于获得大量细胞.其具有自我更新能力、多分化潜能和强大的免疫调节能力,同时能够分泌多种细胞因子,调节机体微环境,是目前干细胞应用的理想种子细胞.该文从ADSCs的定位、分离、表面标记物、增殖分化能力等方面阐述了ADSCs生物学特性,同时对ADSCs的分泌功能及分泌功能研究情况进行综述.以此为理论基础通过对ADSCs的深入研究,使其有望成为细胞治疗和组织工程应用的优秀种子细胞.