为阐明Sh2 甜玉米(Zea mays subsp. saccharata Sturt.)种子萌发过程中关键水解酶对种子贮藏物质利用的作用,以Sh2 甜玉米自交系BF109 和Q267 的种子为材料,对种子萌发2、4、6、8 和10 d 时贮藏物质的消耗量和利用率以及总淀粉酶和蔗糖合成酶的活性进行了测定,并采用实时荧光定量PCR 技术对9 个相关基因的表达特性进行了分析。结果表明:种子萌发6 d 时2 个自交系的单粒种子贮藏物质消耗量大幅度提高,说明种子内的贮藏物质进入快速分解阶段。随萌发时间的延长,2 个自交系的单粒种子贮藏物质消耗量逐渐升高,而贮藏物质利用率则呈先升高后降低的趋势;总体上看,自交系BF109 的单粒种子贮藏物质消耗量显著高于自交系Q267(P<0. 05),而其贮藏物质利用率则显著低于后者。随萌发时间的延长,2 个自交系种子内的总淀粉酶和蔗糖合成酶活性也总体呈先升高后降低的趋势,并且自交系BF109 种子内2 种酶活性基本上低于或显著低于自交系Q267。实时荧光定量PCR分析结果表明:在种子萌发2 ~10 d 期间,2 个自交系种子中9 个α-淀粉酶和蔗糖合成酶相关基因的相对表达量均有较大差异,但7 个α-淀粉酶相关基因(包括α-Amy1A、α-Amy2A、α-Amy3A、α-Amy3B、α-Amy3C、α-Amy3D 和α-Amy3E)的相对表达量均在萌发前期较高,利于合成α-淀粉酶并参与淀粉水解;α-Amy1A、α-Amy2A、α-Amy3D和SuSy-2 基因的相对表达量在种子萌发2 ~ 10 d 均较高,而α-Amy3A、α-Amy3B、α-Amy3C、α-Amy3E 和SuSy-3基因的相对表达量仅在种子萌发2 d 时较高,说明α-Amy1A、α-Amy2A、α-Amy3D 和SuSy-2 基因可能是Sh2 甜玉米种子萌发过程中的关键水解酶基因。总体来看,自交系Q267 种子中相关基因的相对表达量显著高于自交系BF109,这可能是导致自交系Q267 种子中总淀粉酶和蔗糖合成酶活性及贮藏物质利用率较高的主要原因。

In order to clarifying the effect of key hydrolytic enzymes on storage substance utilization in seed of Sh2 sweet corn (Zea mays subsp. saccharata Sturt.) during seed germination process, taking seeds of inbred line BF109 and Q267 of Sh2 sweet corn as materials, consumption and utilization rate of storage substances and activities of total amylase and sucrose synthase were detected when seed germinated for 2, 4, 6, 8 and 10 d, and expression characteristics of nine related genes were analyzed by real-time fluorescence quantitative PCR technology. The results show that consumption of storage substances in single seed of two inbred lines increases greatly when seed germinates for 6 d, meaning that storage substances in seed enter fast decomposition stage. With prolonging of germination time, consumption of storage substances in single seed of two inbred lines increases gradually, while utilization rate of storage substances appears the trend of firstly increasing and then decreasing. On the whole, consumption of storage substances in single seed of inbred line BF109 is significantly higher than that of inbred line Q267 (P<0. 05), while its utilization rate of storage substances is significantly lower than that of the latter. With prolonging of germination time, activities of total amylase and sucrose synthase in seed of two inbred lines also generally appear the trend of firstly increasing and then decreasing, and activities of two enzymes in seed of inbred line BF109 are basically lower or significantly lower than those of inbred line Q267. Analysis result of real-time fluorescence quantitative PCR shows that during seed germination for 2-10 d, there is a great difference in relative expression of nine genes related to α-amylase and sucrose synthase in two inbred line seeds, but relative expressions of seven genes related to α-amylase including α-Amy1A, α-Amy2A, α-Amy3A, α-Amy3B, α-Amy3C, α-Amy3D and α-Amy3E all are higher at the early germination stage, which is beneficial to synthetize α-amylase and involve in starch hydrolysis. Relative expressions of α-Amy1A, α-Amy2A, α-Amy3D and SuSy-2 genes all are higher during seed germination for 2-10 d,while those of α-Amy3A,α-Amy3B,α-Amy3C,α-Amy3E and SuSy-3 genes are higher only when seed germinates for 2 d, meaning that α-Amy1A, α-Amy2A, α-Amy3D and SuSy-2 genes are probably key hydrolytic enzyme genes of Sh2 sweet corn during seed germination process. Overall, relative expressions of related genes in seed of inbred line Q267 are significantly higher than those of inbred line BF109; it may be the main reason for causing higher activities of total amylase and sucrose synthase and higher utilization rate of storage substances in seed of inbred line Q267.