Protein Differences between Two Isogenic Cultivars of Barley (Hordeum vulgare L.) that Differ in Sensitivity to Photoperiod and Far-Red Light

Abstract

A photoperiodically sensitive cultivar of barley (Hordeum vulgare L. Shabet) and an isogenic, single-gene recessive mutant of this genotype that is insensitive to photoperiod (BMDR-1) were grown under continuous cool white light with or without supplemental far-red fluorescent light. BMDR-1 initiates flowers 6 days after germination, irrespective of light treatment, whereas BMDR-8 remains vegetative for at least a week longer, even in continuous light. When far-red light is added, the delay of flowering in BMDR-8 is overcome and both genotypes initiate floral primordia at the same time. Total phenol extracted proteins of seedlings of both genotypes were resolved by two-dimensional sodium dodecyl sulfate-polyacrylamide gel electrophoresis. No protein differences were found between the genotypes when isoelectric focusing gels were run in the first dimension. Two qualitative genotypic differences were found when nonequilibrium pH gradient gel electrophoresis was run in the first dimension. An 85-kilodalton polypeptide (A) and a 26-kilodalton polypeptide (B) were always present in BMDR-8 but never found in BMDR-1. The levels of A appeared to decrease from the BMDR-8 during the first 3 days of far-red treatment but did not disappear completely even after 6 days of growth in the presence of farred. Polypeptide B decreases rapidly in continuous cool white light but is stabilized by far-red. The phytochrome content of BMDR-1 was found to be greater than that for BMDR-8. This increase appears to be caused by the type I (etiolated-tissue abundant) phytochrome pool, even in plants grown in continuous light.Despite the fact that the control of flowering by daylength has been intensively investigated for more than 70 years (13), the fundamental cellular and biochemical basis for this regulation remains unresolved. Nevertheless, photoperiodicallysensitive plants provide an important experimental tool that can be used to manipulate the onset of floral induction. The

A Photoperiod-Insensitive Barley Line Contains a Light-Labile Phytochrome B1

“…However, the difference in flowering time between the genotypes is very significant under the given 12-h photoperiods. BMDR-1 is a very-early flowering genotype and was already in floral stage 4 by d 18, whereas BMDR-8 was still at stage 2 (Principe et al, 1992). Although flowering was not affected by these EOD treatments, the number of tillers formed was significantly affected (Table II).…”

“…3 and 4), residual levels of phyA may remain higher in BMDR-1, leading to enhanced sensitivity to photoperiod. ELISA measurements following growth for 7 d in the light (Principe et al, 1992) had measurable levels of phyA, which were significantly higher in BMDR-1 than in BMDR-8. In addition, the decrease in phyB levels in the light in BMDR-1 may decrease the levels of a floral inhibitor, which, together with the increase in phyA, would result in complete day neutrality.…”

“…However, phy-3 maps to the same chromosome as ea k (Ppd-H2), which may be allelic to BMDR-1. Principe et al (1992) found BMDR-1 to contain about twice the amount of total phytochrome and to differ from BMDR-8 with respect to two other proteins of 26 and 85 kD. However, these two proteins, which are always absent in the mutant genotype, do not decrease in the wild type in response to FR.…”

“…Addition of FR throughout a long photoperiod (24 h) completely overcomes the delay in flowering caused by short days (12 h) in the wild type, allowing it to flower as early as BMDR-1 (Principe et al, 1992). Wild-type plants grown under short photoperiods (12 h) with supplemental FR flower as early as plants grown in long days (24 h) without FR.…”

“…However, these two proteins, which are always absent in the mutant genotype, do not decrease in the wild type in response to FR. The increased level of spectrophotometrically detectable total phytochrome was found to be largely accounted for by an increase in phyA (Principe et al, 1992), but nothing was known about the regulation of phyB levels. The hy3 mutant in Arabidopsis , the ma 3 R mutant in sorghum (Childs et al, 1992), the ein mutant in Brassica rapa (Devlin et al, 1992), and the lh mutant in cucumber (Lopez-Juez et al, 1992) all flower early and lack a light-stable phyB protein.…”