Down-regulation of phytochrome mRNA abundance by red light and benzyladenine in etiolated cucumber cotyledons

Abstract

Northern blot analysis revealed that a single 4.2 kb phytochrome mRNA species was detectable in cotyledons excised from five-day-old etiolated cucumber seedlings. Intact etiolated five-day-old cucumber seedlings were given a red light or benzyladenine treatment, and cotyledons were harvested at various times following treatment. The abundance of phytochrome mRNA in the cotyledons was quantitated using 32P-labeled RNA probes and slot blot analysis. By 2 h after irradiation the phytochrome mRNA level was reduced to 40% of the initial abundance and reaccumulation began by 3 h after irradiation. Reaccumulation of phytochrome mRNA to the time-zero dark control level was achieved by 10 h after treatment. A decrease in phytochrome mRNA abundance was evident by 2 h after benzyladenine treatment, and a maximal reduction to 45% of the time-zero dark control was attained by 4 h after treatment. No recovery of the phytochrome mRNA level was evident by 8 h after benzyladenine treatment. The abundance of actin mRNA was unaffected by benzyladenine treatment.

Transient Down-Regulation of Phytochrome mRNA Abundance in Etiolated Cucumber Cotyledons in Response to Continuous White Light

“…The size of the band was estimated to be 4.2 kb, consistent with previous estimates (5,9). The regions of little phy probe hybridization in the low mol wt smear correspond to the positions of the 18S and 25S ribosomal RNAs (Figs.…”

“…High stringency washes of blots hybridized with a probe that is likely to be poorly conserved between type I-encoding and other phy mRNAs suggest that it is type I-encoding phy mRNA that reaccumulates during exposure to CWL. Although type I-encoding phy mRNA has been previously demonstrated to reaccumulate during darkness after a red light pulse (2,5), no previous data have shown that phy mRNA Analyses of cab mRNA induction and rRNA in total RNA could reaccumulate to substantial levels during a CWL treatom cucumber cotyledons. A, RNA blot analysis of CWLment.…”

“…Cucumber (Cucumis sativus L. cv Marketer) seedlings were grown as described (5). Seedlings used as dark controls were harvested in total darkness.…”

Photomorphogenesis and phyfohormones

“…The transcription of numerous chloroplastic genes is induced by light and CKs (Cohen et al 1988;Bracale et al 1988). Benzyl-adenine inhibits the transcription of the PHYA gene (Cotton et al 1990), as does light. The synthesis of isopentenyl-adenosine is induced by R, an effect reversed by FR (Qamaruddin & Tillberg 1989).…”

Oat phytochrome A mRNA degradation appears to occur via two distinct pathways.

“…Polysomal RNA was isolated as described by Byrne et al (1993). RNA gel blots, hybridization with antisense RNA probes, and liquid scintillation spectroscopy were performed as previously reported (Cotton et al, 1990;Seeley et al, 1992).…”