About the Cover
SPINDLY (SPY) is a negative regulator of gibberellin (GA) responses. On pages 92-102, Greenboim-Wainberg et al. report that spy mutants are resistant to exogenously applied cytokinin, indicating that SPY acts as both a repressor of GA responses and a positive regulator of cytokinin signaling. The authors also examined the effects of GA on cytokinin responses using transgenic Arabidopsis expressing the cytokinin biosynthetic gene isopentenyl transferase (IPT) from Agrobacterium under the control of a carpel-specific promoter. As shown in the cover image, the carpels of IPT-expressing transgenic plants produced numerous ectopic trichomes, in contrast with wild-type Arabidopsis, which are hairless. Repeated treatments with exogenous GA completely suppressed formation of ectopic trichomes, suggesting that GA affects cytokinin responses. From their analysis of spy mutant plants, the authors concluded that the effect of GA on cytokinin responses occurs at least partly through SPY. This article is also highlighted in the In This Issue on pages 1-3.
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Copyright © 2007 by the American Society of Plant Biologists
