PRFLL - A PINUS-RADIATA HOMOLOG OF FLORICAULA AND LEAFY IS EXPRESSED IN BUDS CONTAINING VEGETATIVE SHOOT AND UNDIFFERENTIATED MALE CONE PRIMORDIA

dIn angiosperms, the formation of the flower meristem is controlled by partially redundant flower meristem identity genes of which FLORICAUL A (FLO)/LEAFY (LFY) plays a central role. It is not known whether form ation of reproductive organs of pre-angiosperm species is similarly re gulated. Recently, a FLO/LFY-like cDNA, NEEDLY (NLY), has been cloned in a conifer species Pinus radiata (D. Don). Here we report cloning of a different Pinus radiata FLO/LFY-like cDNA, PRFLL. PRFLL had two lar ge regions of high similarity to angiosperm FLO/LFY orthologues: amino acids 61-126 and 247-406 (50% and 81% identity, and 75% and 88% simil arity, respectively, to LFY) and shorter regions of local similarity. Overall identity was 53% to LFY and 61% to NLY. Phylogenetic analysis of deduced protein sequences including partial LFY-like sequences from Pseudotsuga menziesii indicated that conifer proteins constituted a s eparate clade that could be divided into two groups represented by NLY and PRFLL. In contrast to angiosperms, both conifers had two paralogo us proteins resembling LFY. Northern hybridisation analysis revealed e xpression of PRFLL in vegetative buds of juvenile, adolescent and matu re trees. The transcript was not detected in vascular cambium, roots o r secondary needles. To follow PRFLL expression during the early stage s of cone development we analysed a temporal series of buds containing cone primordia, and developing cones, using Northern hybridisation an d confocal microscopy in parallel. PRFLL mRNA was detected in buds fro m dominant and subordinate branches, in which cone and shoot primordia develop, and in developing male cones but not in developing female co nes. Expression was particularly high in buds containing axillary prim ordia prior to their differentiation as male cone primordia. This is c onsistent with PRFLL being involved in determination of the male cone primordium identity.