ADP-glucose Pyrophosphorylase Activity in Relation to Yield Potential of Wheat: Response to Independent and Combined High Temperature and Drought Stress
ADP-glucose pyrophosphorylase (AGPase) activity in the developing grains of two contrasting wheat cultivars WH730 (thermo-tolerant) and UP2565 (thermo-sensitive) was determined in relation to their allosteric effectors and grain growth. The developing grains (35 days after anthesis) were excised from the middle portion of spikes of wheat genotypes subjected to high temperature, drought and their combination at booting, post-anthesis and booting+post-anthesis. The impact of stress treatments was studied by measuring starch content and yield attributes in relation to AGPase activity. AGPase, a key enzyme for starch synthesis, is allosterically activated by 3-phosphoglyceric acid (3-PGA) and inhibited by inorganic phosphate (Pi). Sensitivity of AGPase towards individual and combined high temperature and drought has not been adequately investigated, therefore the present study analyzed AGPase activity, its sensitivity to allosteric effectors under influence of high temperature, drought in order to elucidate the relationship of AGPase with starch accumulation and grain growth. Significant difference in behavior of the enzyme and its allosteric effectors were observed between the two cultivars under high temperature and/or drought. AGPase activity was substantially decreased by high temperature, drought and was found to be positively correlated with the 3-PGA, starch accumulation and yield attributes, while negatively correlated with Pi content. The results showed that effects of high temperature and drought were additive and more severe at booting+post-anthesis stage. Such studies might help in understanding the control mechanisms associated with the pathway of starch biosynthesis and thus provide chemical means to manipulate starch content vis-à-vis grain yield under heat and drought stress.
KeywordsTriticum aestivum stress tolerance AGPase allosteric effectors starch wheat
high temperature along with drought
days after anthesis
days after sowing
permanent wilting point
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