Multiple functions of gibberellin in modulating plant height, stem strength and drought tolerance

Abstract

Abstract Maize is one of the most widely grown crops in the world. Since the increasing demand of maize supply and extreme weather effects on maize yield, breeding of maize varieties possessing increased yield and enhanced tolerance against biotic/abiotic stresses becomes critical. Gibberellin (GA) plays an important role in regulating diverse aspects of plant height, stem growth and plant responses under drought stress. In this study, a dwarf maize mutant was screened from an EMS-induced mutant library of maize B73. The mutated gene was identified to be KS, which transcripts 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 amount was verified in ks3-1. A significantly decreased stem strength of the ks3-1, compared with that of wild type B73, was found. Significant decreases in the cellulose and lignin content, 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 rate of both wild type B73 and ks3-1decreased 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 would shed light on the importance of GA and GA defective mutants in genetic improvement of maize and breeding maize varieties.