Roses are among the most widely produced cut flowers, with important ornamental and economic value in the flower market. In order to investigate how to regulate flowering periods, the negative regulator of GA biosynthesis RcSPY was cloned from Rosa chinensis and ectopically expressed in tobacco. The overexpression of RcSPY in SPY4 transgenic tobacco significantly increased plant height. Antisense interference with the conserved SPY domain of RcSPY led to GA accumulation in SPY5 transgenic tobacco plants, and antisense interference with the conserved TPR repeats of RcSPY resulted in late flowering in SPY6 transgenic tobacco plants. This result suggests that RcSPY is a negative regulator of GA biosynthesis, since the knock-down of RcSPY increased GA content. However, other phenotypes displayed by transgenic tobacco plants may not be caused by changes of GA content, but rather be the direct effects of RcSPY. Therefore, RcSPY not only participates in GA biosynthesis, but also plays a role in other vegetative and reproductive plant behaviors not related to GA. This result provides theoretical support for the molecular breeding of new cultivars of rose plants.
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