Biol 352 Lecture 10 Brassinosteroids February 7, 2007.

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Presentation transcript:

Biol 352 Lecture 10 Brassinosteroids February 7, 2007

Review: ABA ABA is the major hormone responsible for seed dormancy and water stress response. Key enzymes for biosynthesis: ZEP (ABA1), NCED (VP14), and ABA-aldehyde oxidase (ABA3). ABA antagonizes the action of GA in seed germination. ABA controls stomatal guard cell closure/opening. ABA signaling in stomatal guard cells: Ca2+, K+, H+.

Lecture Outline: Chemical structure of Brassinosteroids (BRs) Bioassays for BRs Biosynthesis of BRs Function of BRs: cell elongation and cell division Summary

Learning Objectives: Reading: Learn to use bioassays to distinguish BRs from other plant hormones Define key enzymes in BR biosynthesis Determine the role of BRs in cell elongation and cell division Reading: 4th Ed, Plant Physiology, Taiz & Zeiger, Chapter 24: p617-633

The Structures of Brassinosteroids BRs are polyhydroxylated steroid hormones. Brassinolide (BL) is the most active BR.

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Summary: Brassinosteroids (BRs) are polyhydroxylated steroid hormones. Brassinolide (BL) is the most active BR. Bioassays can be used to distinguish BRs from other plant hormones. Deficiency in BR biosynthesis results in dwarfism. BRs promote both cell elongation and cell division.