A photoperiod-insensitive barley line contains a light-labile phytochrome B

Abstract

Barley (Hordeum vulgare L.) is a long-day plant whose flowering is enhanced when the photoperiod is supplemented with far-red light, and this promotion is mediated by phytochrome. A chemically mutagenized dwarf cultivar of barley was selected for early flowering time (barley maturity daylength response [BMDR]-1) and was made isogenic with the cultivar Shabet (BMDR-8) by backcrossing. BMDR-1 was found to contain higher levels of both phytochrome A and phytochrome B in the dark on immunoblots with monoclonal antibodies from oat (Avena sativa L.) that are specific to different members of the phytochrome gene family. Phytochrome A was light labile in both BMDR-1 and BMDR-8, decreasing to very low levels after 4 d of growth in the light. Phytochrome B was light stable in BMDR-8, being equal in both light and darkness. However, phytochrome B became light labile in BMDR-1 and this destabilization of phytochrome B appeared to make BMDR-1 insensitive to photoperiod. In addition, both the mutant and the wild type lacked any significant promotion of flowering in response to a pulse of far-red light given at the end of day, and the end-of-day, far-red inhibition of tillering is normal in both, suggesting that phytochrome B is not involved with these responses in barley.

Figure 1

Western blots of 4-d-old etiolated shoots of BMDR-1 (left) and BMDR-8 (right) immunostained with the MAbs Pea-25 and O-22. Each lane was loaded with 105 μg (P-25) or 121 μg (O-22) of total protein and each represents a separate extract from replicate samples. IgG, Nonimmune mouse IgG used as the control. Molecular masses of the protein standards are indicated. The original blots were digitized at 400 DPI using a Canon CJ-10 color scanner, labeled with Adobe PhotoShop 4.0, and printed on a Hewlett-Packard LaserJet 4 MV printer. phy, Phytochrome.

Figure 2

Western blots of 4-d-old-etiolated shoots of BMDR-1 (left) and BMDR-8 (right) probed with the MAbs GO-7 and GO-5. Each lane was loaded with 190 μg of total protein and each represents a separate extract from replicate samples. IgG, Nonimmune mouse IgG used as the control. Molecular masses of the protein standards are indicated. The original blots were digitized as in the Figure 1 legend.

Figure 3

Western blots of 4-d-old-etiolated shoots or those exposed to 4 d of continuous CW of BMDR-1 (top) or BMDR-8 (bottom) immunostained with O-22. Each lane was loaded with 150 μg of total protein extracted from 4-day-old-etiolated (lanes DD) or deetiolated (lanes CW) shoots, and each lane represents a separate extract from replicate samples. The original blots were digitized as in the Figure 1 legend.

Figure 4

Western blots of 4-d–old-etiolated shoots or those exposed to 4 d of continuous CW of BMDR-1 (top) or BMDR-8 (bottom) immunoanalyzed with GO-7. Each lane was loaded with 150 μg of total protein extracted from 4-d-old-etiolated (DD) or deetiolated (CW) shoots, and each lane represents a separate extract from replicate samples. The original blots were digitized as in the Figure 1 legend.