In a complex set of pathways, the product of general sterol synthesis campesterol is converted by several cytochrome P450 monooxygenases to other BRs and ultimately to BL ( Fujioka and Yokota, 2003 Bishop, 2007). Conversely, BR over-accumulation or hyper-responses enhance cell elongation ( Wang et al, 2001 Mora-Garcia et al, 2004).īiosynthesis of brassinolide (BL), the biologically most active BR, is well characterized. Mutants impaired in synthesizing, perceiving or signalling of BRs consequently display dramatic growth defects, such as decreased cell elongation resulting in pleiotropic dwarf phenotypes ( Clouse, 2001). BRs act as essential regulators of cell elongation, cell division and differentiation and participate in many aspects of development ( Clouse, 2001 Bishop and Koncz, 2002 Haubrick and Assmann, 2006). One group of plant hormones is the brassinosteroids (BRs), which are sterol derivatives, structurally similar to mammalian sex steroid hormones and ecdysteroids of insects ( Grove et al, 1979). Plant hormones are organic substances that function as signalling molecules and act at low concentrations to regulate the growth and development of plants. Moreover, we show that CESTA subnuclear localization is BR regulated and discuss a model, in which CESTA interplays with BEE1 to control BR biosynthesis and other BR responses. We provide evidence that CESTA interacts with its homologue BEE1 and can directly bind to a G-box motif in the promoter of the BR biosynthesis gene CPD. Loss-of-function analysis and the use of a dominant repressor version revealed functional overlap among CESTA and its homologues and confirmed the role of CESTA in the positive control of BR-biosynthetic gene expression. ces-D was isolated in a screen of Arabidopsis mutants by BR over-accumulation phenotypes. In this study, we identify the transcription factor CESTA as a regulator of BR biosynthesis. Although it is recognized that the rapid adaptation of de novo synthesis has a key role in adjusting required BR levels, our knowledge of the mechanisms governing feedback control is limited. A tight control of BR homeostasis is vital for modulating their impact on growth responses. Brassinosteroids (BRs) are steroid hormones that are essential for the development of plants.
0 kommentar(er)
