Is Petal Senescence Due to Sugar Starvation? (UPDATE ON SENESCENCE)

To monitor the expression of T-DNA-tagged plant genes in vivo, a collection of 20,261 transgenic lines of Arabidopsis (Columbia-0) were generated with the promoter trap vector pTluc, which carries a promoterless firefly luc (luciferase) reporter gene linked to the right T-DNA border. By detection of bioluminescence in 3-week-old seedlings, 753 lines were identified showing constitutive, organ-specific, and stress-responsive luciferase expression patterns. To facilitate the identification of well-defined luciferase expression patterns, a pooled seed stock was established. Several lines showed sugar, salt, and abscisic acid (ABA)-inducible luciferase activity. Segregation analysis of 215 promoter trap lines indicated that about 50% of plants contained single insertions, whereas 40% carried two and 10% carried three or more T-DNA tags. Sequencing the T-DNA insert junctions isolated from 17 luciferase-expressing lines identified T-DNA tags in 5ʹ- and 3ʹ-transcribed domains and translational gene fusions generated by T-DNA insertions in exons and introns of Arabidopsis genes. Tissue specific expression of eight wildtype Arabidopsis genes was confirmed to be similar to the luminescence patterns observed in the corresponding luciferase-tagged lines. Here, we describe the characterization of a transcriptional luc reporter gene fusion with the WBC-type ABC transporter gene At1g17840. Expression of wild-type and luciferase-tagged At1g17840 alleles revealed similar induction by salt, glucose, and ABA treatments and gibberellin-mediated down-regulation of ABAinduced expression. These results illustrate that luciferase gene traps are well suited for monitoring the expression of stress-responsive Arabidopsis genes in vivo.