N. Ngai et al., LIGHT-INDUCED TRANSCRIPTIONAL REPRESSION OF THE PEA AS1 GENE - IDENTIFICATION OF CIS-ELEMENTS AND TRANSFACTORS, Plant journal, 12(5), 1997, pp. 1021-1034
Here, we examine the cis-elements and trans-factors affecting the expr
ession of asparagine synthetase (AS) genes whose transcription is nega
tively regulated by light. The promoters for the AS1 and AS2 genes of
pea were isolated, sequenced, and functionally dissected for their abi
lity to confer regulated expression to the GUS reporter gene in transg
enic tobacco. Histochemical analysis of transgenic plants demonstrated
that the AS1 and AS2 promoters show identical patterns of cell-specif
ic expression. The more highly active AS1 promoter was further demonst
rated to confer negative light-regulation to the GUS gene in transgeni
c tobacco. Deletion analysis and gain-of-function experiments showed t
hat 124 bp of the AS1 promoter was sufficient to confer light-activate
d repression to a heterologous promoter. Potential conserved transcrip
tion regulatory elements, Box B, Box C, and Box C' within this region
were shown to bind to nuclear proteins by gel shift analysis. A light-
specific DNA:protein interaction was detected with Box B. The nuclear
factors that bind to Box C and C' elements of AS1 are competed by a pu
tative repressor element 'RE1' defined previously in the oat phytochro
me gene whose transcription is also repressed by light. The Box B and
C/C'-Box/RE1-binding factors were found in nuclear extracts of tobacco
, pea, and Arabidopsis and may therefore be universal factors involved
in light-activated transcriptional repression.