Production of a-amylase during the germination of rice grains is thought to play an important role for tolerance to anoxia of these cereal grains. Under aerobic conditions a-amylases production is enhanced in response to gibberellins produced by the embryos, but the role of these hormones is less clear under anoxia. In this paper we analysed a-amylase gene expression in a rice mutant (Tan-ginbozu) severely impaired in gibberellin biosynthesis. Expression of a-amylase genes others than the gibberellin-induced Amy1A gene is observed. The expression of the Amy3D gene, which does dot require gibberellins to be induced, is high under anoxia in the Tan-ginbozu mutant suggesting that germination under anoxia can proceed thanks to the activity of the a-amylase isoform encoded by the Amy3D gene. Amy3D gene expression is repressed in the presence of high levels of soluble carbohydrates, indicating that the anaerobic expression of this gene can be triggered by a lower carbohydrate content of rice grains kept under anoxia. Germination under anoxia of Tan-ginbozu grains can proceed even in absence of exogenously-added gibberellic acid. Overall, results indicate that gibberellins are not required for the anaerobic germination of rice grains.
Gibberellins are not required for rice germination under anoxia
Loreti E;
2003
Abstract
Production of a-amylase during the germination of rice grains is thought to play an important role for tolerance to anoxia of these cereal grains. Under aerobic conditions a-amylases production is enhanced in response to gibberellins produced by the embryos, but the role of these hormones is less clear under anoxia. In this paper we analysed a-amylase gene expression in a rice mutant (Tan-ginbozu) severely impaired in gibberellin biosynthesis. Expression of a-amylase genes others than the gibberellin-induced Amy1A gene is observed. The expression of the Amy3D gene, which does dot require gibberellins to be induced, is high under anoxia in the Tan-ginbozu mutant suggesting that germination under anoxia can proceed thanks to the activity of the a-amylase isoform encoded by the Amy3D gene. Amy3D gene expression is repressed in the presence of high levels of soluble carbohydrates, indicating that the anaerobic expression of this gene can be triggered by a lower carbohydrate content of rice grains kept under anoxia. Germination under anoxia of Tan-ginbozu grains can proceed even in absence of exogenously-added gibberellic acid. Overall, results indicate that gibberellins are not required for the anaerobic germination of rice grains.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
