CORRECT BLUE-LIGHT REGULATION OF PEA LHCB GENES IN AN ARABIDOPSIS BACKGROUND

Irradiation of etiolated Arabidopsis or pea, or dim-red-light-grown pe a seedlings with a single, short (under 10 s) pulse of blue light (thr eshold at 0.1 mu mol/m(2)) is sufficient to induce the expression of s pecific members of the Lhcb gene family including the pea Lhcb14 gene and the Arabidopsis Lhcb13 gene. Other Lhcb genes, such as the pea L hcb13 gene and the Arabidopsis Lhcb1*1 and 1*2 genes are unaffected b y this blue-light treatment. Transgenic Arabidopsis bearing pea Lhcb1 3::Gus (beta-glucuronidase), pea Lhcb14::Gus or Arabidopsis Lhcb1*3:: Gus constructs were used to determine if pea and Arabidopsis employ a similar mechanism to achieve blue-light induced Lhcb expression. Exami nation of the respective Gus expression patterns in white-light-grown seedlings indicates that the pea promoters are active and properly exp ressed in the Arabidopsis background. Irradiation of dark-grown Arabid opsis with a 20 s pulse of blue light with a total fluence of 100 mu m ol/m(-2) results in expression of the pea Lhcb14::Gus (beta-glucuroni dase) construct, but not of the pea Lhcb13::Gus construct indicating that the pea promoters respond correctly to blue Light in the Arabidop sis background. Fluence-response, time-course and reciprocity characte ristics for the blue-light-induced expression of the pea Lhcb14::Gus construct closely resemble those of the endogenous Arabidopsis Lhcb ge nes, confirming the proper interpretation of the Arabidopsis blue-ligh t-signaling mechanism by the pea Lhcb14 promoter and suggesting that the signaling mechanisms in the two plants are very similar, if not id entical. Fluence response data for the steady-state level of transcrip t derived from an Arabidopsis Lhcb13::Gus construct extending 200 bp upstream of the site of transcription indicate that the blue light res ponsive element(s) are contained within this 200 bp region.