Jointly silencing BoDWARF, BoGA20ox and BoSP (SELF-PRUNING) produces a novel miniature ornamental Brassica oleracea var. acephala f. tricolor variety

Abstract

The ornamental Brassica oleracea var. acephala f. tricolor is a good winter and spring foliage plant. Plant architecture is an important agronomic trait of plants, especially for ornamental plants with high ornamental and economic value. In this study, three miniature-related genes, BoDWARF, BoGA20ox and BoSP (SELF-PRUNING), were cloned and their tissue-specific expression patterns were analyzed. The results showed that the three genes were all highly expressed in young leaves and flowers, followed by the lateral roots, seeds and stems. To further achieve the purpose of miniaturization of plants, an RNAi expression vector, jointly targeting BoDWARF, BoGA20ox and BoSP, was constructed and transformed into kale plants. Smaller plant size and slower growth and development speed of flowers and roots were observed in jointly silenced kales. Brassinosteroids and gibberellin contents in leaves and flower buds of transgenic plants were significantly decreased. Furthermore, the expressions of brassinolide-, gibberellin- and flowering-related genes were down-regulated by varying degrees in silenced plants. These results suggest that BoDWARF, BoGA20ox and BoSP play important roles in plant architecture, and that brassinolide and gibberellin are important hormones controlling plant growth and architecture. This miniaturization strategy of kale provides an efficient approach for cultivation of new varieties of ornamental plants and crops.