title: Function of B-BOX under shade.
abstract: Plants are capable of perceiving changes in the light environment and finely adjust their growth and development. Reductions of red to far-red ratio (R:FR) generated by an increase of the plant canopy above the plant are sensed by the phytochrome system triggering the shade-avoidance syndrome (SAS) that includes elongation of vegetative structures, reduction of branching and acceleration of flowering. Albeit the SAS is a strategy of major adaptative significance in plant communities, involving massive changes in gene expression, our knowledge of the SAS signaling network is still fragmented. By a selection and characterization of a T-DNA mutant with a long hypocotyl under shade, we identified BBX21, a protein with two B-box domains involved in the SAS. BBX21 belongs to a small eight member family of B-box containing proteins with both opposite and additive functions in the SAS signaling. BBX21 down-regulates the gene expression of auxin, brassinosteroid and ethylene signaling pathway components under shade. Furthermore BBX21 is a transcription factor that interacts genetically with COP1. We propose a model in which a dynamic balance of positive and negative B-box transcriptional regulators acts as a gas-and-brake mechanism into the COP1 signaling to regulate the expression of SAS.
authors.affiliation: IFEVA, Facultad de Agronomía, Universidad de Buenos Aires y Consejo Nacional de Investigaciones Científicas y Técnicas, Buenos Aires, Argentina.
authors.forename: Carlos D
authors.initials: CD
authors.lastname: Crocco
authors.forename: Magnus
authors.initials: M
authors.lastname: Holm
authors.forename: Marcelo J
authors.initials: MJ
authors.lastname: Yanovsky
authors.forename: Javier F
authors.initials: JF
authors.lastname: Botto
mesh_terms: D060406:Brassinosteroids; D002777:Cholestanols / Q000378:metabolism; D003624:Darkness; D015536:Down-Regulation / Q000235:genetics; D005030:Ethylenes / Q000378:metabolism; D018506:Gene Expression Regulation, Plant; D007210:Indoleacetic Acids / Q000378:metabolism; D010641:Phenotype; D063245:Plant Development; D010940:Plant Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D010944:Plants / Q000235:genetics / Q000378:metabolism*; D017434:Protein Structure, Tertiary; D015398:Signal Transduction / Q000235:genetics; D013260:Steroids, Heterocyclic / Q000378:metabolism
chemical_list: D060406:Brassinosteroids; D002777:Cholestanols; D005030:Ethylenes; D007210:Indoleacetic Acids; D010940:Plant Proteins; D013260:Steroids, Heterocyclic; C036216:ethylene; C023623:brassinolide