开花期短期缺氮处理提高黄瓜维生素C含量的机理研究（英文）

Mechanism of short-term nitrogen deficiency at flowering stage improving content of vitamin C in cucumber

AsA,也被称为维生素C,是植物中丰富的抗氧化剂。已有研究发现,在短期缺氮处理下,黄瓜中AsA含量提高。但是具体的调控机制并不明确。该研究中,以开花结果期的水培黄瓜植株为研究对象,分别探究短期缺氮处理对黄瓜果实和叶片中H2O2,MDA,AsA含量的影响,以及相关酶活性和AsA-GSH相关基因表达量的影响,据此研究短期缺氮条件下黄瓜AsA含量提高的机理。结果表明:与对照相比,在短期缺氮处理下,第7天果实中MDA和H2O2分别增加了1倍和0.8倍;处理1(T1,开花期营养液中无氮)果实中SOD酶活性,POD酶活性和CAT酶活性在第7天分别增加了60%,21%和74%;在处理第5天,果实和叶片中的T-AsA含量分别增加了70%和17%。短期缺氮处理下,T1叶片中APX-1,APX-3,APX-4,APX-5,AO-4,GR-1和GR-2等基因的表达水平在第1天显着上调;在T1果实中,AO-1,MDHAR-1,MDAHR-3,GR-2和APX-5等基因的的转录表达在第1天高于对照。T1果实中APX活性在第5天增加了51.6%;处理1叶片和果实中MDHAR酶活性在第3天分别增加了59.6%和24.8%;处理1果实中DHAR活性在第3天增加了109%。由此可知,花期短期的缺氮处理促进了黄瓜果实和叶片中T-AsA的积累和As A-GSH循环途径相关酶活性的提高,同时As A-GSH循环途径中的部分基因表达量上调。

AsA(L-ascorbic acid),also known as vitamin C,is an abundant antioxidant in plants.The previous study found that the AsA level of cucumber was higher under the short-term nitrogen deficiency than control(without nitrogen deficiency).However,the regulatory mechanism is not explicit.In this study,the mechanism of short-term nitrogen deficiency at the flowering stage improving AsA content of cucumber was studied.The effect of relative enzyme activities and AsA-GSH recycling-related genes expression profiles,as well as the hydrogen peroxide(H2O2),malondialdehyde(MDA)and AsA contents were studied in hydroponic cucumber under short-term nitrogen deficiency,respectively.Based on this,the mechanism of AsA content increasing in cucumber under short-term nitrogen deficiency was studied.The results showed that under nitrogen deficiency,the content of MDA and H2O2 increased by 1-and 0.8-fold in the fruits of T1(without nitrogen at flowing stage)compared with CK(nitrogen content of 12 mmol/L at flowing stage)on the 7th day after nitrogen deficiency treatment,respectively.The superoxide dismutase(SOD)activity,peroxidase(POD)activity and catalase(CAT)activity in the fruits of T1 increased by 60%,21%and 74%respectively on the 7th day.Moreover,the total AsA(T-AsA)content in fruits and leaves were increased by 70%and 17%on the 5th day,respectively.The expression levels of APX-1,APX-3,APX-4,APX-5,AO-4,GR-1 and GR-2 were significantly up-regulated on the 1st day in leaves of T1 under short-term nitrogen deficiency.In the fruits of T1,transcripts of AO-1,MDHAR-1,MDAHR-3,GR-2 and APX-5 were higher than that of the control on the 1st day.The APX activity of T1 fruits increased by 51.6%on the 5th day.The MDHAR activity in leaves and fruits of T1 increased by 59.6%and 24.8%on the 3rd day,respectively.And the DHAR activity in fruits of T1 increased by 109%on the 3rd day.It can be seen that short-term nitrogen deficiency at flowering stage promoted the accumulation of T-AsA in cucumber fruits and leaves,the activities of related enzymes in AsA-GSH recycling pathway increased,and the expression level of genes in AsA-GSH recycling pathway were up-regulated.