HIGH-TEMPERATURE AFFECTS THE ACTIVITY OF ENZYMES IN THE COMMITTED PATHWAY OF STARCH SYNTHESIS IN DEVELOPING WHEAT ENDOSPERM
HIGH-TEMPERATURE AFFECTS THE ACTIVITY OF ENZYMES IN THE COMMITTED PATHWAY OF STARCH SYNTHESIS IN DEVELOPING WHEAT ENDOSPERM
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DOI：
10.1071/pp9930197
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发表时间：
1993-01-01
期刊：
影响因子：
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通讯作者：
JENNER, CF
中科院分区：
文献类型：
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作者：
HAWKER, JS;JENNER, CF
小麦穗在灌浆期暴露于高温（35 ℃）长达10天，并将蔗糖转化为淀粉途径中的五种酶的活性与保持在较低温度（21 ℃白天/16 ℃夜晚）下的穗进行比较。比较了两个已知花后耐高温性不同的小麦品种。在每粒的基础上，蔗糖合成酶和ADP葡萄糖焦磷酸化酶的活性在整个保持在21/16 ℃的穗中在开花后16 - 32天之间没有很大变化，而UDP葡萄糖焦磷酸化酶和可溶性淀粉合成酶活性则随着发育进程的推进而下降，热穗籽粒中可溶性淀粉合成酶活性在1天内下降到约1 - 100%。未加热谷物中的值的一半，并且3天的额外加热没有进一步降低活性。不溶性淀粉合成酶活性没有显着降低加热。与可溶性淀粉合成酶相比，ADP葡萄糖焦磷酸化酶活性受热影响较慢，降低程度较小。蔗糖合成酶和UDP葡萄糖焦磷酸化酶的活动没有受到影响或仅略有减少，这种减少的一部分可能是由于先进的发展在较高的温度。在恢复实验中，耳朵被短暂加热，然后恢复到21/16摄氏度几天。ADP葡萄糖焦磷酸化酶和可溶性淀粉合成酶的活性恢复在较冷的条件下，但其他两种酶一般只保持或失去进一步的活动。从这些酶的活性与淀粉沉积速率的比较，并考虑到加热的影响，有人提出，加热对最终谷物干重的影响是由于所观察到的可溶性淀粉合成酶活性的降低。
Ears of wheat were exposed for up to 10 days during the grain-filling stage to high temperature (35-degrees-C) and activities of five enzymes in the sucrose to starch pathway were compared to those in ears maintained at lower temperature (21-degrees-C day/16-degrees-C night). Two cultivars of wheat known to differ in their post-anthesis tolerance of high temperature were compared. On a per grain basis, the activity of sucrose synthase and of ADPglucose pyrophosphorylase in ears maintained at 21/16-degrees-C throughout did not change greatly between days 16 and 32 after anthesis, whereas UDPglucose pyrophosphorylase and soluble starch synthase activities declined with advancing development.Soluble starch synthase activity in grains of heated ears was decreased within 1 day to about one-half of the value in unheated grains, and 3 days' additional heating did not reduce the activity much further. Insoluble starch synthase activity was not significantly reduced by heating. Compared to soluble starch synthase, ADPglucose pyrophosphorylase activity was more slowly affected and decreased to a lesser extent by heat. Sucrose synthase and UDPglucose pyrophosphorylase activities were either not affected or only slightly reduced; part of this reduction could be due to advanced development at the higher temperature. In recovery experiments ears were heated for brief periods and then returned to 21/16-degrees-C for a few days. ADPglucose pyrophosphorylase and soluble starch synthase activities recovered in the cooler conditions but the other two enzymes generally only maintained or lost further activity. From a comparison of the activities of these enzymes with the rate of starch deposition, and by taking into account the effects of heating, it is proposed that the influence of heating on final grain dry weight is attributable to the observed reductions of soluble starch synthase activity.