Pea LATE BLOOMER1 Is a GIGANTEA Ortholog with Roles in Photoperiodic Flowering, Deetiolation, and Transcriptional Regulation of Circadian Clock Gene Homologs

Abstract

Genes controlling the transition to flowering have been studied in several species, including Arabidopsis (Arabidopsis thaliana) and rice (Oryza sativa), but have not yet received much attention in legumes. Here, we describe a new allelic series of lateflowering, photoperiod-insensitive mutants in the pea (Pisum sativum) LATE BLOOMER1 (LATE1) gene and show that LATE1 is an ortholog of Arabidopsis GIGANTEA. Mutants display defects in phytochrome B-dependent deetiolation under red light and in the diurnal regulation of pea homologs of several Arabidopsis circadian clock genes, including TIMING OF CAB1, EARLY FLOWERING4, and CIRCADIAN CLOCK ASSOCIATED1/LATE ELONGATED HYPOCOTYL. 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 a FLOWERING LOCUS T (FT) homolog FTL in long days but cause only minor alteration to the rhythmic expression pattern of the only known group Ia CONSTANS homolog COLa. The late-flowering phenotype of late1 mutants can be completely rescued by grafting to the wild type, 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 sterile nodes (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.

VEGETATIVE1 is essential for development of the compound inflorescence in pea

“…The origins of the veg1/psfulc-1, det-2, pim-1 and gigas-2 mutants have been previously described 11,16,17,40 . The psfulc-2 mutant was generated from line NGB5839 by EMS mutagenesis 27 . The psfulc-3 mutant was isolated by reverse screening in an EMS-mutagenized TILLING population of cultivar Caméor 28 .…”

“…Forward screening of an ethyl methanesulfonate (EMS)-mutagenized population 27 identified a single M 2 plant in which secondary inflorescences were replaced by vegetative branches, as in veg1 (Fig. 4c).…”

Molecular characterisation of flowering genes in Pongamia Pinnata

“…PpCOL-1 showed a morning phase expression rhythm, which is similar to the CO-like in other species under the LD condition; COL1 and COL2 in Arabidopsis (Ledger et al, 2001), PsCOLa in pea (Hecht et al, 2007), and also several other COLs in Medicago (Wong et al, 2014). Their expression levels peak during the morning, then decline during the afternoon.…”

“…In legumes such as Pisum sativum (pea), Glycine max (Soybean) and Medicago truncatula (Medicago), studies on flowering gene orthologues have discovered several genes with a conserved role in the regulation of flowering time in response to photoperiod. However, the function of these CO homologues in photoperiod response is still not clear (Hecht et al, 2005;Hecht et al, 2007;Jiang et al, 2011;Liu et al, 2011;Watanabe et al, 2011;Weller et al, 2012;Wong et al, 2014).…”

Co-option of a photoperiodic growth-phase transition system during land plant evolution

“…Homologues of GI and FKF1 have been reported in a wide variety of vascular plants from lycophytes to angiosperms 8 . The function of GI in the regulation of photoperiodic flowering has been shown to be common across several angiosperm species [9][10][11][12][13] . However, neither GI nor FKF1 orthologues have yet been identified in fully sequenced non-vascular plants, including the moss Physcomitrella patens 8 .…”