Abstract
AbstractThe effects of powdery mildew on gene expressions and activities of carbon (C) metabolism enzymes in Zhengmai 103 (resistant) and Xi'nong 979 (susceptible) are studied. Under severe powdery mildew, expressions and activities of sucrose synthase, uridineâdiphosphate glucose pyrophosphorylase, glyceraldehydeâ3âphosphate dehydrogenase (GAPDH), and cytosolic αâ1,4âglucan phosphorylase decrease at 20 or 25â30 days after anthesis, and total soluble sugars content also decreases. It indicates that the first part of C metabolism (sucrose degradation) changes and total C flux reduces. Meanwhile, decreases in expressions and activities of adenosineâdiphosphate glucose pyrophosphorylase (AGPase), soluble starch synthase (SSS), starchâbranching enzyme I and II (SBEI and SBEII), and plastidic αâ1,4âglucan phosphorylase coincide with decreases in amylopectin content, whereas increases in granuleâbound starch synthase I (GBSSI) expression and activity coincide with increases in amylose content. It shows that the second part of C metabolism (starch synthesis) changes. Therefore, powdery mildew alters C metabolism. In addition, it also induces defense responses in grains, such as the upâregulation of a defenseârelated protein endogenous αâamylase/subtilisin inhibitor. Since GAPDH, AGPase, SSS, SBEII, and GBSSI are regulated by redox, changes of C metabolism are mainly regulated by cellular redox status.
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