强、弱筋小麦籽粒形成期蔗糖、淀粉合成相关酶活性及其与氮代谢的关系

Activities of Enzymes Involved in Sucrose and Starch Synthesis during Grain Filling and the Relation to Nitrogen Metabolism in Strong- and Weak-Gluten Wheat Cultivars

2005—2006年生长季,以小麦强筋品种藁城8901和弱筋品种豫麦50为材料,研究了灌浆期籽粒和旗叶氮代谢底物含量与相关酶活性变化、蔗糖淀粉合成相关酶活性及籽粒淀粉积累特征,分析了氮代谢与籽粒淀粉积累的关系。结果表明,旗叶蔗糖合酶(SS)和磷酸蔗糖合酶(SPS)、籽粒腺苷二磷酸葡萄糖焦磷酸化酶(AGPP)、可溶性淀粉合酶(SSS)、束缚态淀粉合酶(GBSS)和淀粉分支酶(SBE)活性均呈单峰曲线变化。两品种比较,除AGPP活性峰值豫麦50低于藁城8901外,其他酶活性峰值均是豫麦50高于藁城8901。相关分析表明,藁城8901支链淀粉积累速率与SS、SPS、AGPP和SBE活性呈极显著正相关,相关系数分别为0.9377**、0.8857**、0.6489**和0.5980**;直链淀粉积累速率与SS、SPS活性呈极显著正相关,相关系数分别为0.7616**和0.7750**。豫麦50支链淀粉积累速率与SS、SPS、AGPP、GBSS和SBE活性呈极显著或显著正相关,相关系数分别为0.8182**、0.6762**、0.7028**、0.8749**和0.5433*;直链淀粉积累速率与SS、SPS和SBE活性呈极显著正相关,相关系数分别为0.8528**、0.8428**和0.8603**。两品种硝酸还原酶(NR)、谷氨酰胺合成酶(GS)活性在开花后逐渐降低,且藁城8901的NR活性一直高于豫麦50。硝态氮和氨态氮含量与NR、GS活性呈极显著正相关;藁城8901的NR、GS活性与SS、SPS活性呈显著负相关,而豫麦50只有GS与SPS达显著负相关(r=-0.5212*)。上述结果表明,不同品质类型小麦籽粒淀粉合成积累受氮代谢相关酶活性的影响,藁城8901较高的NR活性抑制与蔗糖合成有关酶SS、SPS的活性,导致淀粉合成积累速率降低。由此可见,SPS/NR比值对淀粉合成具有重要调节作用。

The strong- and weak-gluten cultivars are two typical patterns of high-quality wheat for different end-uses, between which many differences exist in the synthesis, accumulation, concentration, and components of both protein and starch in grain. The experiment was conducted at Tai＇an experimental station of Shandong Agricultural University in 2005-2006 growth season. A strong-gluten cultivar Gaocheng 8901 and a weak-gluten cultivar Yumai 50 were used to compare the contents of NO3^--N, NH4^＋-N and activities of enzymes relating to nitrogen metabolism, sucrose and starch syntheses and the starch accumulation during grain filling, and to characterize the relationship between nitrogen and carbon metabolisms during grain development. The results indicated that the activities of sucrose synthase （SS）, sucrose-phosphate synthase （SPS）, adenosine diphosphorate glucose pyrophrylase （AGPP）, soluble starch synthase （SSS）, granule-bound starch synthase （GBSS）, and starch branching enzyme （SBE）performed in the pattern of a single-peak curve during grain filling. The peak values of SS, SPS, SSS, GBSS, and SBE activities were higher in Yumai 50 than in Gaocheng 8901 except AGPP. The accumulation rate of amylopectin was highly significantly correlated with the activities of SS （r=-0.9377^＊＊）, SPS （r=0.8857^＊＊）, AGPP （r=-0.6489^＊＊）, and SBE （r=-0.5980^＊＊） in Gaocheng 8901, however, the accumulation rate of amylose was highly significantly correlated with the activities of SS （r=-0.7616^＊＊） and SPS （r=-0.7750^＊＊）. The accumulation rate of amylopectin was significantly or highly significantly correlated with the activities of SS （r=-0.8182^＊＊）, SPS （r=0.6762^＊＊）, AGPP （r=-0.7028^＊＊）, GBSS （r=0.8749^＊＊）, and SBE （r=-0.5433^＊） in Yumai 50, and the accumulation rate of amylose was highly significantly correlated with the activities of SS （r=-0.8528^＊＊）, SPS （r=-0.8428^＊＊）, and SBE（r=0.8603^＊＊）. The activities of both nitrate reductase （NR） and glutamine synthetase （GS） exhibited a gradually decreased trend in the processs of grain filling in both cultivars, the activities of NR and GS in Gaocheng 8901 were higher than those in Yumai 50. The contents of NO3^--N and NH4^＋-N were highly significantly positively correlated with the activities of NR and GS in both cultivars. In Gaocheng 8901, the activities of NR and GS were negatively correlated with the activities of SS and SPS, but in Yumai 50 only the negative correlation of the activities between GS and SPS was significant （r=-0.5212^＊）. Based on the results mentioned-above it was found that the starch synthesis and accumulation in grains of the different cultivars were influenced by the activities of the enzymes involved in nitrogen metabolism. The higher activity of NR caused the activities of both SS and SPS to be decreased, resulting in the decline of starch accumulation rate. This finding here supported the assumption that the ratio of SPS to NR plays an important role in starch synthesis and accumulation in wheat grains.