Identification,Phylogeny, and Comparative Expression of the Lipoxygenase Gene Family of the Aquatic Duckweed,Spirodela polyrhiza,during Growth and in Response to Methyl Jasmonate and Salt

Lipoxygenases (LOXs) (EC 1.13.11.12) catalyze the oxygenation of fatty acids and produce oxylipins, including the plant hormone jasmonic acid (JA) and its methyl ester, methyl jasmonate (MeJA). Little information is available about the LOX gene family in aquatic plants. We identified a novel LOX gene family comprising nine LOX genes in the aquatic plant Spirodela polyrhiza (greater duckweed). The reduced anatomy of S. polyrhiza did not lead to a reduction in LOX family genes. The 13-LOX subfamily, with seven genes, predominates, while the 9-LOX subfamily is reduced to two genes, an opposite trend from known LOX families of other plant species. As the 13-LOX subfamily is associated with the synthesis of JA/MeJA, its predominance in the Spirodela genome raises the possibility of a higher requirement for the hormone in the aquatic plant. JA-/MeJA-based feedback regulation during culture aging as well as the induction of LOX gene family members within 6 h of salt exposure are demonstrated.     

外源MeJA诱导烟草叶面防御反应

以中烟100为材料,研究了茉莉酸甲酯(MeJA)喷施后,烟草叶面腺毛密度类型、腺毛分泌物合成积累及叶片对蚜虫抗性的变化规律,探讨了烟草叶面腺毛的防御反应模式和作用机制。结果表明,MeJA处理后,烟草叶片对蚜虫的驱避作用明显增强,新生叶片叶面腺毛密度增加,尤其是长柄多细胞腺头腺毛密度的变化达到显著水平。GC/MS分析表明,MeJA处理使叶面分泌物含量增加,并在处理后第7天达到最大值。其中,西柏烷类二萜化合物含量增幅最大。但RT-PCR分析发现,西柏三烯一醇合成酶基因(CBT)、西柏三烯一醇羟化酶基因(CYP71D16)在转录水平上并没有明显变化,表明烟草叶面腺毛物质的合成和分泌可能具有复杂的转录后调控机制。     

MeJA处理对枇杷果实采后抗氧化活性的影响

为了探讨MeJA处理对枇杷果实抗氧化能力的影响,研究了10μmol/L MeJA处理的"大红袍"枇杷果实在1℃贮藏过程中维生素C、总酚、总黄酮、总类胡萝卜素含量及抗氧化活性的变化。结果表明,枇杷果实在贮藏过程中维生素C和总黄酮含量下降,而总酚和总类胡萝卜素含量呈先上升后下降的趋势。10μmol/L MeJA处理可显著抑制果实中维生素C和总黄酮含量的下降,促进贮藏前期总酚和总类胡萝卜素含量的上升。在1℃贮藏过程中,枇杷果实DPPH和超氧阴离子自由基清除能力随着贮藏时间的延长呈先上升后下降趋势,并且抗氧化活性的变化与总酚和总类胡萝卜素含量的变化呈显著正相关,而与维生素C和总黄酮含量的变化相关性较低。这表明MeJA是通过影响枇杷果实中酚类和类胡萝卜素物质的代谢来维持枇杷果实采后较高的抗氧化能力和营养价值。     

Synergistic Effect of Methyl Jasmonate and Abscisic Acid Co-Treatment on Avenanthramide Production in Germinating Oats

The oat (Avena sativa L.) is a grain of the Poaceae grass family and contains many powerful anti-oxidants, including avenanthramides as phenolic alkaloids with anti-inflammatory, anti-oxidant, anti-itch, anti-irritant, and anti-atherogenic activities. Here, the treatment of germinating oats with methyl jasmonate (MeJA) or abscisic acid (ABA) resulted in 2.5-fold (582.9 mg/kg FW) and 2.8-fold (642.9 mg/kg FW) increase in avenanthramide content, respectively, relative to untreated controls (232.6 mg/kg FW). Moreover, MeJA and ABA co-treatment synergistically increased avenanthramide production in germinating oats to 1505 mg/kg FW. Individual or combined MeJA and ABA treatment increased the expression of genes encoding key catalytic enzymes in the avenanthramide-biosynthesis pathway, including hydroxycinnamoyl-CoA:hydrocyanthranilate N-hydroxycinnamoyl transferase (HHT). Further analyses showed that six AsHHT genes were effectively upregulated by MeJA or ABA treatment, especially AsHHT4 for MeJA and AsHHT5 for ABA, thereby enhancing the production of all three avenanthramides in germinating oats. Specifically, AsHHT5 exhibited the highest expression following MeJA and ABA co-treatment, indicating that AsHHT5 played a more crucial role in avenanthramide biosynthesis in response to MeJA and ABA co-treatment of germinating oats. These findings suggest that elicitor-mediated metabolite farming using MeJA and ABA could be a valuable method for avenanthramide production in germinating oats.     

茉莉酸甲酯处理对采后葡萄果实酚酸合成和抗氧化活性的影响及其机理研究

以‘巨峰’葡萄果实(Vitis vinifera L.× V. labrusca L. cv. ‘Kyoho’)为试材,研究了10μmol/L茉莉酸甲酯(methyljasmonate,MeJA)熏蒸处理对采后葡萄果实在1℃贮藏期间酚酸含量和抗氧化活性的影响,并从苯丙烷类代谢角度分析了相关机理。结果显示：10μmol/L MeJA处理可显著抑制葡萄果实贮藏期间腐烂率和落粒率的上升,诱导苯丙烷类代谢关键酶苯丙氨酸解氨酶(PAL)、肉桂酸羟化酶(C4H)和查耳酮合成酶(CHS)活性的上升并延缓对香豆酰-CoA连接酶(4-CL)活性的下降,同时显著提高果实主要酚酸(没食子酸、咖啡酸、原儿茶酸、丁香酸和p-香豆酸)和总酚含量并维持了DPPH自由基清除率和总还原力。结果表明：MeJA可通过调控葡萄果实苯丙烷类代谢相关酶系的活性,从而有效诱导果实中酚酸的合成并维持果实贮藏期间抗氧化活性,最终提高了果实采后食用和营养品质。     

Methyl jasmonate enhances biocontrol efficacy of Rhodotorula glutinis to postharvest blue mold decay of pears

The effect of Rhodotorula glutinis treatment alone or in combination with methyl jasmonate (MeJA) in controlling blue mold decay, the natural fungal decay of pears and the postharvest quality parameters including fruit firmness, total soluble solids, titratable acidity, and ascorbic acid were investigated. The combination of methyl jasmonate (200 μM) and R. glutinis (1 × 10⁸ CFU/ml) was a more effective approach to reduce the disease incidence and lesion diameter of blue mold decay of pears than the application of MeJA or R. glutinis alone after incubation for 7 d at 20 °C. The natural fungal decay of pears treated with the application of R. glutinis combined with MeJA resulted in reduced average decay incidence of 10.42% or 4.16%, respectively, compared with 27.17% or 20.83% in the control fruits following storage at 20 °C for 15 d or 4 °C for 60 d followed by 20 °C for 15 d. The combined treatment did not impair quality parameters of fruits under both conditions.     

普通烟草脂氧合酶基因家族鉴定及表达模式分析

脂氧合酶（LOX）是脂肪酸代谢途径的关键酶,在植物的生长发育及多种逆境胁迫响应过程中发挥重要作用。本研究对烟草基因组中的LOX家族成员进行鉴定,并利用进化分析、共线性分析和表达分析等方法解析LOX家族成员的潜在生物学功能。结果表明,在普通烟草中共鉴定得到18个LOX基因,其中12个LOX基因被锚定在染色体上。系统进化分析表明,普通烟草中新鉴定的LOX家族成员被分为9-LOX和13-LOX两个亚家族,其中13-LOX又可被分为Type I和Type II两个亚类。共线性分析表明,烟草NtLOX07、NtLOX10基因分别与拟南芥AtLOX05、AtLOX01基因形成同源基因对,并且大部分同源基因之间具有相似的表达模式。表达模式分析发现,普通烟草LOX基因表达具有一定的组织特异性,并且NtLOX06等基因能够被机械损伤和茉莉酸甲脂（MeJA）处理显著诱导。因此,普通烟草LOX家族成员可能在植物胁迫响应过程中发挥着重要的作用。     

采后茉莉酸甲酯处理对富士苹果青霉病和贮藏品质的影响

以富士苹果为材料,研究采后茉莉酸甲酯（methyl jasmonate,MeJA）处理对果实损伤接种扩展青霉的抑制效果及对过氧化氢（H2O2）含量、超氧化物歧化酶（SOD）、过氧化氢酶（CAT）活性及果实贮藏品质的影响。结果表明,100 μmol/L MeJA处理10 min对苹果果实青霉病的抑制效果最好,MeJA处理提高了果实SOD活性,促进了果实体内H2O2的积累,抑制了CAT的活性。此外,外源MeJA处理明显提高了果实抗坏血酸含量,降低了贮藏期间果实的质量损失率,对果肉硬度、可溶性固形物和可滴定酸含量无显著影响。由此推测,采后经MeJA处理的苹果果实抗病性提高和果实品质保持与抗氧化能力的提高有关。     

茉莉酸甲酯处理对采后葡萄离区膜脂过氧化及果实落粒的影响

分析了外源10μmol/L茉莉酸甲酯(M ethyl jasm on ate,MeJA)熏蒸处理对"巨峰"葡萄果穗在1℃贮藏期间离区膜脂过氧化及果实落粒的影响。结果表明,10μmol/LMeJA处理可显著降低葡萄果实冷藏期间落粒率、腐烂率和褐变指数,维持果实感官品质,同时显著诱导贮藏期间葡萄果穗离区组织中活性氧代谢酶(SOD、CAT、APX和POD)活性的上升并抑制超氧阴离子和羟基自由基生成量的增加。经MeJA处理的离区细胞膜中不饱和脂肪酸亚油酸和亚麻酸含量明显高于对照水平,而饱和脂肪酸棕榈酸和硬脂酸含量、相对电导率和MDA含量却显著低于对照水平。这些结果说明,MeJA处理可通过提高葡萄离区组织中活性氧代谢酶活性来减慢离区膜脂过氧化进程并维持离区细胞结构,从而降低了贮藏期间葡萄果实落粒率,改善了果实品质。