Genetic engineering of lignin biosynthesis pathway improved stem bending disorder in cut gerbera (Gerbera jamesonii) flowers

Gerbera (Gerbera jamesonii) is an important commercial species of cut flowers all around the world. Stem bending is a major disorder in cut gerbera flowers caused mainly by the lack of mechanical support in the flower stem. Lignin is the component of plant cell walls that provides strength. Three major enzymes comprise the pathway of lignin anabolism including peroxidase (POD), cinnamyl alcohol dehydrogenase (CAD), and cinnamoyl-CoA reductase (CCR). In this study, three overexpressed mutants for each of these major genes were generated and analyzed for their role in stem bending. Comparing the pod transgenic plants with ccr and cad mutants indicated that pod plants had the highest lignin content. Compared to wild-type (WT) plants, the highest vase life, membrane stability and solution uptake were obtained in gerbera pod mutants. Therefore, it appears that higher lignin contents can decrease stem bending and improve cell wall rigidity of cut gerbera flowers. These results also suggest that POD is a key gene in the biosynthesis of lignin in gerbera.