Starch accumulation and enzymes activities associated with starch synthesis in maize kernels

Chinese. 分析玉米籽粒发育过程中灌浆速率、蔗糖代谢、淀粉积累及相关酶活性的变化，了解玉米籽粒淀粉积累的控制机理。以高淀粉玉米（费玉3号）和普通玉米（豫玉22）为材料，进行大田试验，采用比色法测定蔗糖含量，采用双波长法测定淀粉及其组分含量的变化动态，参照Douglas等的方法测定蔗糖合成酶（SS）活性，参照Nakamura等的方法测定腺苷二磷酸葡萄糖焦磷酸化酶（ADPGPPase）、束缚态淀粉合成酶（GBSS）、淀粉分支酶（SBE）和去分支酶（DBE）的活性。灌浆速率、蔗糖含量、淀粉积累速率及SS、GBSS、SBE活性的高低均存在明显的基因型差异，授粉后10 d后，费玉3号上述指标均高于豫玉22。相关性分析表明，灌浆中后期SS活性与淀粉积累速率和籽粒灌浆速率均呈（极）显著正相关；ADPGPPase、DBE活性与淀粉积累速率和籽粒灌浆速率的相关性未达到显著水平；GBSS活性与直链淀粉积累速率呈极显著正相关，与籽粒灌浆速率相关性不显著；SBE活性与支链淀粉积累速率和籽粒灌浆速率呈极显著正相关。ADPGPPase和DBE不是影响玉米籽粒中淀粉积累的关键酶；SS是淀粉积累的限速因子；GBSS对直链淀粉积累起重要的调节作用；SBE对支链淀粉积累起关键作用。

English. Filling rate and starch accumulation in developing maize kernel were analyzed. The changes of enzyme activities associated with sucrose metabolism and starch biosynthesis were investigated. The purpose is to analyze the enzymatic mechanisms responsible for starch synthesis. Two types of maize (Zea mays) cultivars, high starch maize (Feiyu3) and normal maize (Yuyu22), were grown in a corn field. Sucrose content was determined with colorimetry. Content of starch and its component was measured with the method of double-wavelength. Sucrose synthase (SS) activity was assayed using the method described by Douglas, et al. ADP-glucose pyrophosphorylase (ADPGPPase), granule-bound starch synthase (GBSS), starch branching enzyme (SBE) and starch debranching enzyme (DBE) activities were assayed using the method described by Nakamura et al. Kernel filling rate, sucrose content, starch accumulating rates and the activities of SS, GBSS, SBE of Feiyu3, which has high starch content, were significantly higher than those of Yuyu22, which has low starch content, after 10 DAP (days after pollination). Correlation analysis indicated that ADPGPPase and DBE were not correlated with starch accumulating rates and kernel filling rate, but SS activity at the middle and late periods were (highly) significantly correlated with starch accumulating rates and kernel filling rate. GBSS activity was highly significantly correlated with amylose accumulating rate, but not correlated with kernel filling rate. SBE activity was highly significantly correlated with amylopectin accumulating rate and kernel filling rate. It is not ADPGPPase and DBE, but SS is the rate-limiting factor of starch biosynthesis in developing maize kernels. GBSS has an important effect on amylose accumulation. SBE has a significant effect on amylopectin accumulation.