米糠稳定化研究进展

稳定化处理是米糠能够有效利用的先决条件。本文介绍米糠稳定化处理的意义、方法及其进展。对米糠稳定化处理的要求、食品用稳定化米糠的质量标准、各种稳定化方法的优缺点及其发展现状作了相应的介绍。     

大豆脂肪氧化酶的遗传规律

通过酶学鉴定，分析研究了大豆脂肪氧化酶（lipoxygenase)简称脂氧酶（lox)的遗传规律，试验证实lox基因突变体酶性失活，酶带缺失为隐性基因，显隐性属质量性状，细胞核遗传，3种lox同功酶非等位基因在同源染色体上分别独立占属一个位点，某一同功酶等位基因降性缺失时，基因遗传遵从3；1独立分配原则；2种非等位基因同时隐性缺失时，缺1和缺2的基因连锁遗传，双缺1和3或双缺2和3的基因分离各自互不干扰，都遵从独立分离规律；3种lox同功酶基因同时隐性缺失时，除lox缺1基因仍接近3：1独立遗传外，缺2和缺3基因都不符合独立传规律，其中缺1和缺2两对隐性缺失基因仍有71．5％的 锁遗传，重组率28．5％，缺2和缺3基因，缺1和缺3基因之间，基因重组率在45％以上，lox完全显性植株为49．3％，缺1为6．9％，缺2为10％，缺3为17．9％，1和2双缺为6．9％，、1和3双缺为0．9％，2和3双缺为5．4％，3种同功酶同时隐性缺失时获得率为2．7％。     

茉莉酸类与光敏核不育水稻N5088S育性的关系

以光敏核不育水稻N5088S为试验材料,研究了茉莉酸类与水稻育性的关系。研究结果表明,茉莉酸甲酯(Methyl jasmonate,MeJA)显著提高不育光温条件下光敏核不育水稻N5088S的花粉染色率和自交结实率,而其生物合成抑制剂水杨苷异羟肟酸(Salicylhydroxamicacid,SHAM)则使可育光温条件下的N5088S花粉染色率和自交结实率显著降低;同时,MeJA提高了N5088S叶片和幼穗的脂氧合酶(LOX)活性,而SHAM则使其活性降低。在幼穗分化的第3~8期,N5088S叶片中的LOX活性在可育光温条件下明显高于不育光温条件,而幼穗中的差异不明显。这一结果说明外源MeJA可使不育光温条件下的光敏核不育水稻N5088S的育性在一定程度上得到恢复,并提示内源茉莉酸类(JAs)可能参与N5088S的育性转换。     

大豆脂肪氧合酶缺失种质的筛选及脂肪氧合酶的遗传研究

为了发掘大豆脂肪氧合酶缺失种质材料，对中国长江流域及其以南地区14个省（市）211份大豆资源作缺失体种质的筛选以及遗传分析。结果表明，脂肪氧合酶有4种电泳类型：Lox1,Lox2,Lox3a和Lox3b；中国长江流域及其以南地区大豆资源中有丰富的脂肪氧合酶缺失类型，缺失频率为18.48%，其中单一缺失类型较丰富；Lox2,Lox2和Lox3分别受显性基因控制，缺失体则分别受隐性基因控制，控制Lox1和Lox2的基因是紧密连锁遗传的，连锁强度为7.77%，而控制Lox3的基因则是独立遗传的。因此，在无（或少）豆腥味新品种培育和利用上应选育脂肪氧合酶全缺失类型和缺失Lox1,Lox2的类型。     

利用大豆鲜子叶快速检测脂氧酶缺失

脂氧酶是大豆产生豆腥味的主要原因,培育脂氧酶完全缺失大豆新品种可以从加工源头上解决加工去腥难题。在F2分离世代筛选脂氧酶缺失体是无腥味大豆育种的关键。本研究对现有的ISDS-PAGE电泳技术筛选方法进行改进,在苗后子叶展开期,取鲜子叶20 mg,快速无损测定脂肪氧化酶,由过去的播前切粉取样,改为苗后鲜子叶取样,改良后的方法不仅能清晰鉴别Lox-1,2,3三种同工酶缺失与否,同时确保含目标性状个体的正常生长发育,为大豆脂氧酶缺失育种提供技术支持。     

不同基因型大豆种子脂肪氧化酶与己醛生成量的相关性

在添加亚油酸作为反应底物的条件下，以分别含有Lox1Lox3和Lox1Lox2的大豆为材料，研究Lox1Lox3和Lox1Lox2在不同遗传背景下的己醛生成量．结果表明：各个Lox1Lox3材料之间在己醛生成量上存在一定差异，变异系数为6.88％；各个Lox1Lox2材料之间在己醛生成量上也存在一定差异，变异系数为6．51％．但进一步作显著性测验都未能达到显著水平，说明不同遗传背景对大豆种子脂肪氧化酶Lox1Lox3和Lox1Lox2在生成己醛量活性方面没有明显影响。     

Prokaryotic Expression,Purification and Characterization of a Novel Rice Seed L.ipoxygenase Gene OsLOX1

Lipoxygenase （LOX, EC1.13.11.12） is a key enzyme during the degradation of lipids in animals and even plants, and also the first key enzyme responsible for the biosynthesis of jasmonate. To purify and characterize the OsLOX1 gene from rice seeds, the entire coding region of the OsLOX1 gene was inserted into an expression vector pET30a（＋） and transformed into Escherichia coil BL21 （DE3）. Expression of the fusion protein was successfully induced by isopropyl-β-D- thiogalactopyranoside （IPTG） and the purified recombinant protein was obtained by His.Bind Kits. Further assay showed that the purified recombinant protein exhibited the LOX activity. The optimum pH was 4.8 （acetate buffer） and the optimum temperature was 30℃ for the above enzyme. Thus, the recombinant might confer an available usage for the synthesis of jasmonate in vitro, and also provides a possibility for elucidating the inter-relationship between the primary structure of the plant seed lipoxygenase protein and its physiological functions.     

花生种子脂肪氧化酶缺失品种筛选研究

根据花生种子脂肪氧化酶同工酶等电点差异,利用等电聚焦电泳技术,筛选花生种子脂肪氧化酶缺失的品种。结果表明:不同品种花生种子脂肪氧化酶的IEF-PAGE图谱有差异,有些花生品种呈现四条酶带,有些花生品种呈现三条酶带,缺失一条酶带。     

α-Conotoxins and α-Cobratoxin Promote,while Lipoxygenase and Cyclooxygenase Inhibitors Suppress the Proliferation of Glioma C6 Cells

Among the brain tumors, glioma is the most common. In general, different biochemical mechanisms, involving nicotinic acetylcholine receptors (nAChRs) and the arachidonic acid cascade are involved in oncogenesis. Although the engagement of the latter in survival and proliferation of rat C6 glioma has been shown, there are practically no data about the presence and the role of nAChRs in C6 cells. In this work we studied the effects of nAChR antagonists, marine snail α-conotoxins and snake α-cobratoxin, on the survival and proliferation of C6 glioma cells. The effects of the lipoxygenase and cyclooxygenase inhibitors either alone or together with α-conotoxins and α-cobratoxin were studied in parallel. It was found that α-conotoxins and α-cobratoxin promoted the proliferation of C6 glioma cells, while nicotine had practically no effect at concentrations below 1 µL/mL. Nordihydroguaiaretic acid, a nonspecific lipoxygenase inhibitor, and baicalein, a 12-lipoxygenase inhibitor, exerted antiproliferative and cytotoxic effects on C6 cells. nAChR inhibitors weaken this effect after 24 h cultivation but produced no effects at longer times. Quantitative real-time polymerase chain reaction showed that mRNA for α4, α7, β2 and β4 subunits of nAChR were expressed in C6 glioma cells. This is the first indication for involvement of nAChRs in mechanisms of glioma cell proliferation.     

普通小麦籽粒LOX、PPO活性和类胡萝卜素含量 变异及对全麦粉色泽的影响

【目的】研究新鲜全麦粉及储存3个月后全麦粉中脂肪氧化酶（LOX）和多酚氧化酶（PPO）的活性及类胡萝卜素含量的变化情况,分析其色泽性状与LOX、PPO活性和类胡萝卜素含量之间的关系,了解储存时间对全麦粉色泽的影响及其品种间的差异,为全麦粉或面粉色泽的改良和相关的育种工作提供参考依据。【方法】选用63个普通小麦品种（系）为试验材料,用分光光度计法测定其LOX、PPO活性和类胡萝卜素含量,用色差计法测定全麦粉色泽性状。【结果】品种间LOX、PPO活性、类胡萝卜素含量及其它色泽性状差异显著或极显著;新鲜全麦粉和存储3个月的全麦粉的LOX、PPO活性变化较大,储存期间LOX、PPO活性丧失较快,类胡萝卜素含量相对稳定;储存3个月后的白度和亮度等色泽性状存在一定程度的变化,但变化不大。新鲜全麦粉的白度和亮度均与PPO活性呈极显著负相关,黄度与类胡萝卜素含量呈极显著正相关,LOX活性与类胡萝卜素含量呈极显著负相关,而LOX活性与白度、亮度和黄度间相关均不显著;储存3个月的全麦粉的白度和亮度仅与PPO活性呈极显著负相关。【结论】全麦粉色泽改良中,PPO活性和类胡萝卜素的遗传控制是关键;通过储存全麦粉或面粉的方式并不能大幅度的提高其亮度、白度和降低黄度。所以,遗传育种方法是改良小麦粉白度性状和类胡萝卜素含量等品质性状的重要途径。