title: New lv Mutants of Pea Are Deficient in Phytochrome B.
abstract: The lv-1 mutant of pea (Pisum sativum L.) is deficient in responses regulated by phytochrome B (phyB) in other species but has normal levels of spectrally active phyB. We have characterized three further lv mutants (lv-2, lv-3, and lv-4), which are all elongated under red (R) and white light but are indistinguishable from wild type under far-red light. The phyB apoprotein present in the lv-1 mutant was undetectable in all three new lv mutants. The identification of allelic mutants with and without phyB apoprotein suggests that Lv may be a structural gene for a B-type phytochrome. Furthermore, it indicates that the lv-1 mutation results specifically in the loss of normal biological activity of this phytochrome. Red-light-pulse and fluence-rate-response experiments suggest that lv plants are deficient in the low-fluence response (LFR) but retain a normal very-low-fluence-rate-dependent response for leaflet expansion and inhibition of stem elongation. Comparison of lv alleles of differing severity indicates that the LFR for stem elongation can be mediated by a lower level of phyB than the LFR for leaflet expansion. The retention of a strong response to continuous low-fluence-rate R in all four lv mutants suggests that there may be an additional phytochrome controlling responses to R in pea. The kinetics of phytochrome destruction and reaccumulation in the lv mutant indicate that phyB may be involved in the light regulation of phyA levels.
authors.affiliation: Department of Plant Science, University of Tasmania, GPO Box 252C, Hobart, Tasmania 7001, Australia (J.L.W., I.C.M., J.B.R.).
authors.forename: J. L.
authors.initials: JL
authors.lastname: Weller
authors.forename: A.
authors.initials: A
authors.lastname: Nagatani
authors.forename: R. E.
authors.initials: RE
authors.lastname: Kendrick
authors.forename: I. C.
authors.initials: IC
authors.lastname: Murfet
authors.forename: J. B.
authors.initials: JB
authors.lastname: Reid