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Molecular mechanisms of pecan flower induction

Randall, J. J., Rascon, A., Heerema, R. J., Potter, M. T.
Acta horticulturae 2015 no.1070 pp. 89-99
Arabidopsis thaliana, Carya illinoinensis, Citrus, Malus domestica, Populus, Pyrus communis, RNA, alternate bearing, apples, flowering, flowers, gene expression, genes, growing season, hormones, juveniles, light quality, pears, pecans, phloem, photoperiod, protein synthesis, reverse transcriptase polymerase chain reaction, shoot meristems, signal transduction, temperature, trees
Flower development initially requires reprogramming of the shoot meristem resulting in a transition from vegetative to floral tissues. Specific genetic switches within the plant that respond to environmental cues such as photoperiod, light quality, temperature, and hormones regulate this reprogramming. Several of these genetic switches were elucidated in the model plant Arabidopsis thaliana and have since been shown to be present in other plants including trees such as poplar (Populus sp.), apple (Malus × domestica), pear (Pyrus communis), and citrus (Citrus spp.). In Arabidopsis, an intricate signaling pathway is initiated when the CONSTANS (CO) protein responds to lengthening days, activating expression of the FLOWERING LOCUS T (FT gene). The FT protein then is transported via the phloem to shoot meristems where it activates expression of genes responsible for floral induction (AP1 and LFY). In poplar and apple, the increase of FT protein expression correlates to an increase in flowering and appears to play a role in the transition of juvenile trees to mature flowering trees. We have recently isolated and sequenced the homologues of the FT and LFY genes from pecan (Carya illinoinensis). We are currently characterizing gene expression of these pecan homologs. Leaflet tissue samples from fruit-bearing and vegetative shoots of mature alternate bearing ‘Wichita’ pecan trees were collected monthly during the 2011 and 2012 growing seasons and stored at -80°C. RNA was isolated from the tissues and analyzed using quantitative reverse transcription PCR. These data will help elucidate the role these genes play in the development of flowers in pecan and may provide new tools for the management of flowering-related challenges in pecan nut production.