Adp-glucose pyrophosphorylase activity in relation to starch accumulation and grain growth in wheat cultivars.

摘要

ADP-glucose pyrophosphorylase (AGPase) activity in the developing grains of four wheat (Triticum aestivum L.) cultivars DL153-2, C306, HD2329 and WH542 grown under normal (27 November) and late (28 December) sown conditions was determined in relation to their grain growth and starch content. In order to analyse the temperature sensitivity of AGPase, excised developing grains (20 days after anthesis) of normal sowing were exposed for 1 h at 25 degrees C, 35 degrees C and 45 degrees C and subsequently analysed for AGPase activity. AGPase activity in the developing grains was also determined in presence of PGA and Pi to evaluate the sensitivity of the enzyme to allosteric effectors. The study showed a highly significant correlation of AGPase activity with starch accumulation and grain growth in wheat under normal sowing but not so under late sowing. However, AGPase was not found to be that sensitive to moderate heat so as to be responsible for decreased starch accumulation and grain growth under late sowing. PGA helped in overcoming inhibition by Pi but did not activate the AGPase further. However, genotypic differences in the sensitivity of AGPase to allosteric effectors were observed. An efficient AGPase insensitive to regulation by PGA and Pi in wheat grain would lead to faster starch accumulation and early falling of grains and may thus avoid extreme terminal high temperature experienced during grain development.