A gibberellin-deficient maize mutant exhibits altered plant height, stem strength and drought tolerance

The reduction in endogenous gibberellin improved drought resistance, but decreased cellulose and lignin contents, which made the mutant prone to lodging. It is well known that gibberellin (GA) is a hormone that plays a vital role in plant growth and development. In recent years, a growing number of studies have found that gibberellin plays an important role in regulating the plant height, stem length, and stressed growth surfaces. In this study, a dwarf maize mutant was screened from an EMS-induced mutant library of maize B73. The mutated gene was identified as KS, which encodes an ent-kaurene synthase (KS) enzyme functioning in the early biosynthesis of GA. The mutant was named as ks3-1. A significant decrease in endogenous GA levels was verified in ks3-1. A significantly decreased stem strength of ks3-1, compared with that of wild-type B73, was found. Significant decreases in the cellulose and lignin contents, as well as the number of epidermal cell layers, were further characterized in ks3-1. The expression levels of genes responsible for cellulose and lignin biosynthesis were induced by exogenous GA treatment. Under drought stress conditions, the survival rate of ks3-1 was significantly higher than that of the wild-type B73. The survival rates of both wild-type B73 and ks3-1 decreased significantly after exogenous GA treatment. In conclusion, we summarized that a decreased level of GA in ks3-1 caused a decreased plant height, a decreased stem strength as a result of cell wall defects, and an increased drought tolerance. Our results shed light on the importance of GA and GA-defective mutants in the genetic improvement of maize and breeding maize varieties.