Phytochrome Control of the Levels of Plastid and N...
The involvement of phytochrome in controlling photogene expression was tested by briefly exposing etiolated maize plants to R（1 min）or to FR（5 min）or to R（1 min）followed by R（5 min）and measuring the relative levels of complementary RNA［see Figure 2（a）］.Morphological changes in plants exposed to different light treatments were checked roughly to verify that the illumination conditions used elicited classical phytochromemediated responses in etiolated maize seedlings.After all the plants were moved to continuous white light for 24 h directly from darkness or exposed to two R pulses each followed by 3 h darkness，those seedlings preilluminated with R pulses showed，more rapid Chl accumulation than seedlings not preilluminated with R pulses.
Figure 2 （a）Scheme of R and FR treatments.Maize plants were grown in the dark for 10 d，then illuminated with R（1 min），FR（5 min），or R/FR（1 min/5 min）at 0 and 3 h，as indicated by the arrows.The leaves were harvested at 6 h.Dark bars represent periods in darkness.（b）Dot hybridization of maize RNA with cloned probes for plastid and nuclear genes.Total RNAs were extracted from dark-grown leaves or leaves illuminated with R，FR，or R/FR，as shown in（a）.Equal amounts of RNA（5 μg）were denatured and spotted onto Gene Screen，hybridized with 32 P-labeled probes，and exposed to X-ray film，as described in“Materials and Methods.”The scanning densitometer values of films from similar expenments are shown in Table 2.(https://www.daowen.com)
