Minisymposium 27: Growth & Vegetative Development

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Abs # M2702: Brassinosteroids signal non-autonomously from the epidermis to control shoot growth

Presenter:	Savaldi-Goldstein, Sigal       Contact Presenter
Authors	Savaldi-Goldstein, Sigal  (A)   Chory, Joanne  (A) (B)
Affiliations:	(A): The Salk Institute (B): Howard Hughes Medical Institute

Brassinosteroids (BRs) are essential for normal plant development. In the absence of BR production or perception, plants exhibit extreme dwarf stature which is attributed to defects in cell expansion and division. Thus far, key players in the BR signaling and biosynthesis pathway have been cloned, but their site of action responsible for the control of plant growth remains unknown. Since BR-signaling does not seem to play a significant role in shoot differentiation, determining where it occurs provides a valuable tool to elucidate the regulation of shoot growth per se. We therefore dissected the interaction and contribution of the outer and inner layers to BR mediated growth responses. To this end we used targeted expression of BR signaling, biosynthesis and catabolic components in their corresponding mutant and wild-type background. Our data suggest that the L1 layer is sufficient to drive shoot growth and that shoot growth depends on available active BRs or active BR signaling in the epidermis. This non-autonomous effect does not involve movement of the transcription factors BES1 or BZR1 nor can it be fully mimicked by their stabilized mutant form, suggesting that factors in addition to BES1 or BZR1 are required for BR control of growth in the L1 layer. Additional aspects of this work will be presented and discussed.