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Plant Physiology Preview Published on April 27, 2007; 10.1104/pp.107.096818
OPEN ACCESS ARTICLE
Received February 1, 2007 Pea LATE BLOOMER 1 Is a GIGANTEA Ortholog with Roles in Photoperiodic Flowering, De-etiolation and Transcriptional Regulation of Circadian Clock Gene Homologs
School of Plant Science, University of Tasmania, Private Bag 55, Hobart, Tasmania 7001, Australia * Corresponding author; email: jim.weller{at}utas.edu.au.
Genes controlling the transition to flowering have been studied in several species, including Arabidopsis and rice, but have not yet received much attention in legumes. Here we describe a new allelic series of late-flowering, photoperiod-insensitive mutants in the pea (Pisum sativum L.) LATE BLOOMER 1 (LATE1) gene, and show that LATE1 is an ortholog of Arabidopsis GIGANTEA. Mutants display defects in phyB-dependent de-etiolation under red light, and in the diurnal regulation of pea homologs of several Arabidopsis circadian clock genes including TOC1, ELF4, and CCA1/LHY. LATE1 itself shows strongly rhythmic expression with a small but distinct acute peak following dark-to-light transfer. Mutations in LATE1 prevent the induction of an FT homolog FTL in long days, but cause only minor alteration to the rhythmic expression pattern of the only known group Ia CO homolog COLa. The late-flowering phenotype of late1 mutants can be completely rescued by grafting to WT, but this rescue is not associated with a significant increase in FTL transcript level in shoot apices. Genetic interactions of late1 with the photoperiod-insensitive early-flowering sn mutant and impairment of the LATE1 diurnal expression rhythm in sn plants suggest that SN may also affect the circadian clock. These results show that several functions of Arabidopsis GIGANTEA are conserved in its pea ortholog, and demonstrate that genetic pathways for photoperiodic flowering are likely to be conserved between these two species. They also suggest that in addition to its role in the floral transition, LATE1 also acts throughout reproductive development.
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