基于生氰糖苷降解途径基因表达特性的木薯品种对二斑叶螨的抗性机制初探

为初步探究生氰糖苷降解途径2个基因α-HNL和β-glu在木薯品种对二斑叶螨抗性中的作用,本研究以抗螨木薯品种‘C1115’‘缅甸’‘SC9’和感螨木薯品种‘SC205’‘面包’‘BRA900’为材料,分析木薯生氰糖苷降解途径基因及其编码的生化酶在二斑叶螨取食木薯品种不同部位叶片（上部、中部和下部）不同时间后（1、4 d）的表达量及酶活性的变化情况。结果表明,α-HNL在感螨木薯品种上部和中部叶片中的表达量随螨害时间的延长而显著降低;在抗螨木薯品种的不同部位叶片中,α-HNL的表达量均随螨害时间的延长而显著升高,并且以中部和下部叶片的升高趋势更为显著。β-glu在抗、感螨木薯品种不同部位叶片中的表达量均很低,难以比较该基因的表达量在不同木薯品种、不同部位叶片受螨害后的变化情况,但在能检测到的少量样品当中,抗螨木薯品种的占比也多于感螨木薯品种。进一步进行酶活性分析结果表明,抗螨木薯品种受螨害后,随着时间的延长,降解途径基因α-HNL编码的α-HNL酶活性呈逐渐升高或维持不变的趋势,并且以中部和下部叶片的升高趋势更为显著,而在感螨木薯品种中,随着螨害时间的延长,α-HNL酶活性则呈逐渐降低或先升高后降低的趋势;β-glu基因编码的β-GLU酶活性在不同木薯品种中均呈较低的水平,这可能与其对应编码的基因表达量低有关,但总体而言,降解途径2个基因编码的降解酶α-HNL和β-GLU在抗螨木薯不同叶片组织中的活性总体上也显著高于感螨木薯。本研究初步揭示了不同木薯品种受螨害不同时间后,生氰糖苷降解基因和酶可能与木薯对二斑叶螨的抗性有关。

Resistance Mechanism of Cassava Cultivars to Tetranychus urticae Based on Gene Expression Characteristics of Cyanogenic Glycoside Degradation Pathway

In order to explore the resistance mechanism of cassava varieties based on the gene expression characteristics of cyanogen glycoside degradation pathway to Tetranychus urticae, this study used mite-resistant cassava cultivars ‘C1115’ ‘Myanmar’ ‘SC9’ and mite-susceptible cassava cultivars ‘SC205’ ‘Mianbao’ ‘BRA900’ as materials to analyze the cyanogen glycoside degradation pathway genes related to plant insect resistance and the biochemical enzymes changes in the leaves of different parts (top, middle and bottom) when those mites fed for 1 d and 4 d, respectively. The results showed that the expression of α-HNL in the top and middle leaves of mite-susceptible cassava varieties decreased significantly with the extension of the mite infestation time. In the leaves of different parts of mite-resistant cassava varieties, the expression level of α-HNL increased significantly with the extension of the mite infestation time, and the increasing trend was more significant in the middle and bottom leaves. The expression of β-glu in the leaves of different parts of the mite-resistant cassava varieties was very low. It is difficult to compare the changes in the expression level of this gene after different cassava varieties and different parts of the leaves are damaged by mites, but it is not detectable. Among a small number of samples, the proportion of mite-resistant cassava varieties was more than that of mite-susceptible cassava varieties. The results of further enzyme activity analysis showed that after the mite-resistant cassava varieties were infested by mites, as time passed, the enzyme activity of α-HNL encoded by the degradation pathway gene α-HNL showed a tendency to gradually increase or remain unchanged, and the rising trend of the middle and bottom blades was more significant. In the mite-susceptible cassava varieties, with the extension of the mite infestation time, the enzyme activity of α-HNL showed a trend of gradual decrease or first increase and then decrease. The β-GLU enzyme activity encoded by the β-glu gene showed low levels in different cassava varieties, which may be related to the low expression of the corresponding encoded gene. But overall, the degrading enzymes α-HNL and β-GLU encoded by the two genes of the degradation pathway in different leaf tissues of mite-resistant cassava were also significantly higher than that of mite-susceptible cassava. This study initially revealed that cyanogenic glycoside degradation genes and enzymes may be related to the resistance of cassava to Tetranychus urticae after different cassava varieties were infested by mites for different periods of time.