Effects of gibberellin on genetic variations in α-amylase production in germinating barley seeds

Abstract

For the purpose of genetically improving α-amylase production in barley malts, the relationship between endogenous gibberellin content and α-amylase activity among varieties of barley was investigated. Endogenous gibberellin content was determined by radioimmunoassay, a very sensitive assay, by which all of the so-called active gibberellins in barley were detected. Among them, GA, was the dominant endogenous gibberellin in germinating barley seeds. At 96 h after imbibition (HAI), α-amylase activities and endogenous active gibberellin contents were correlated among barley varieties. However, cv. Nijo Mochimugi had a low activity compared to endogenous gibberellin content. Interestingly, Nijo Mochimugi showed a lower response to exogenous gibberellin (we think this represents responsiveness to gibberellin in α-amylase induction: RGA) than the other varieties, strongly suggesting that the low α-amylase activity in Nijo Mochimugi resulted from the low RGA. Consequently, it is concluded that α-amylase production is affected by two factors: endogenous active gibberellin content and RGA. Variation in RGA among barley varieties was not due to differences in barley α-amylase/subtilisin inhibitor (BASI) activity. α-Amylase and protease activity induced by exogenous gibberellin were correlated, which suggests that the main mechanism(s) which causes variation in RGA would also involve protease(s) induction.