FT-Like NFT1 Gene May play a role in Flower Transition Induced by Heat Accumulation in Narcissus tazetta var chinensis Xiao-Fang Li, Lin-Yan Jia, Jing Xu, Xin-Jie Deng, Yang Wang, Wei Zhang, Xue-Ping Zhang Qi Fang, Dong-Mei Zhang Yue Sun'and Ling Xu' School of Life Science, East China Normal University, 500 Dongchuan Rd, Shanghai, PR China 200241 Shanghai Institute of Landscape Architecture, 899 Longwu Rd, Shanghai, PR China 200232 Correspondingauthor:E-mail,xfi@bioecnu.edu.cn;Fax,+86-21-62233754. ( Received July 23, 2012; Accepted December 18, 2012) The low-temperature Alowering-response pathway, used as The nucleotide sequence of NFTI reported in this paper has an inductive stimulus to induce flowering in plant species been submitted to NCBl under accession numbers JX316221 for from temperate regions in response to cold temperature, has cDNA and JX316222 for genomic DNA. been extensively studied. However, limited information is available on the flower transition of several bulbous species, Introduction which require high temperature for flower differentiation. Narcissus tazetta var chinensis(Chinese narcissus)exhibits a Timing of transition to flowering in higher plants is controlled 2 year juvenile phase, and flower initiation within its bulbs through environmental and endogenous cues. Genetic and mo- occurs during summer dormancy. The genetic factors that lecular studies in the model plant Arabidopsis thaliana character control flower initiation are mostly unknown in Chinese ize a complex network of genetic pathways that regulate narcissusIn the present study, we found that a high storage fowering(Amasino and Michaels 2010). Vemalization, ambient temperature is necessary for flower initiation. Flower initi- temperature and photoperiod pathways regulate fowering in ation was advanced in bulbs previously exposed to extended response to environmental cues, whereas autonomous, gibberel high temperature. The heat accumulation required for lin and development stage pathways regulate flowering in re- flower transition was also determined. High temperature sponse to endogenous signals (Samach and Wigge 2005, treatment rescued the low flower percentage resulting Kobayashi and Weigel 2007, Farrona et al. 2008 Turck et al. from short storage duration under natural conditions. In 2008, Kim et al. 2009, Mutasa-Gottgens and Hedden 2009, addition, extended high storage temperature was found to Wang et al 2009a, Amasino and Michaels 2010).Several key com increase the fowering percentage of 2-year-old plants, which ponent genes involved in these pathways have orthologs in a wide can be applied in breeding. Narcissus FLOWERING LOCUs variety of plants, induding other monocots and perennials T1(NFT1, a homolog of the Arabidopsis thaliana gene (Amasino 2010). Arabidopsis Flowering Locus T(FT) protein is FLOWERING LOCUS T, was isolated in this study NFT1 tran- now widely accepted as a mobile forigen( Corbesier et al. 2007, scripts were abundant during fower initiation in mature Giakountis and Coupland 2008). FT is activated in the leaf in bulbs and were up-regulated by high temperature The gen- response to an inductive photoperiod, and subsequently moves etic experiments, coupled with an expression profiling assay, to the shoot apex FT interacts with the product of Flowering suggest that NFT1 possibly takes part in flower transition Locus D(FD), a bZIP protein, at the vegetative shoot apex, and control in response to high temperature. then activates transcription of foral meristem genes to start the fowering process(Abe et al. 2005, Wigge et al. 2005). FT orthold Keywords: Flower initiation Narcissus tazetta var. have been discovered in several plant species(Bohlenius et al chinensis·NFT1· Temperature. 2006, Yan et al. 2006, Faure et al. 2007, Gyllenstrand et al. 2007, Abbreviations: CO,CONSTANS; FD, Flowering Locus D, Hayama et aL. 2007, Danilevskaya et al. 2008, Colasanti and Coneva FLC, FLOWERING LOCUS C: FT, FLOWERING LOCUS T: 2009, Hou and Yang 2009, Kikuchi et al. 2009, Komiya et al. 2009, qRT-PCR, quantitative real-time PCR; RACE, rapid ampli- Blackman et al. 2010, Kong et al. 2010) fication of cDNA ednds; SEM, scanning electron microscopy, Seasonal temperature changes elicit seasonal flowering re- SM, shoot meristem; SOC1, SUPPRESSOR OF OVEREX sponses that allow the synchronization of fowering with opti- PRESSION OF CONSTANST; TFL1, TERMINAL FLOWER 1; mal conditions(King and Heide 2009, Hemming and Trevaskis WT, wild type 2011). Several plant species from temperate regions use cold PlantCellPhysiol54(2):270-281(2013)doi:10.1093/pcp/pcs181,availableonlineatwww.pcp.oxfordjournalsorg C The Author 2013. Published by Oxford University Press on behalf of Japanese Society of Plant Physiologis AllrightsreservedForpermissionspleaseemailjournalspermissions@oup.com 270 Plant Cell Physiol. 54(2): 270-281(2013)doi: 10.1093/pcp/pcs181 C The Author 2013.FT-Like NFT1 Gene May Play a Role in Flower Transition Induced by Heat Accumulation in Narcissus tazetta var. chinensis Xiao-Fang Li1,*, Lin-Yan Jia1 , Jing Xu1 , Xin-Jie Deng1 , Yang Wang1 , Wei Zhang1 , Xue-Ping Zhang1 , Qi Fang1 , Dong-Mei Zhang2 , Yue Sun1 and Ling Xu1 1 School of Life Science, East China Normal University, 500 Dongchuan Rd., Shanghai, PR China 200241 2 Shanghai Institute of Landscape Architecture, 899 Longwu Rd., Shanghai, PR China 200232 *Corresponding author: E-mail, xfli@bio.ecnu.edu.cn; Fax, +86-21-62233754. (Received July 23, 2012; Accepted December 18, 2012) The low-temperature flowering-response pathway, used as an inductive stimulus to induce flowering in plant species from temperate regions in response to cold temperature, has been extensively studied. However, limited information is available on the flower transition of several bulbous species, which require high temperature for flower differentiation. Narcissus tazetta var. chinensis (Chinese narcissus) exhibits a 2 year juvenile phase, and flower initiation within its bulbs occurs during summer dormancy. The genetic factors that control flower initiation are mostly unknown in Chinese narcissus. In the present study, we found that a high storage temperature is necessary for flower initiation. Flower initi￾ation was advanced in bulbs previously exposed to extended high temperature. The heat accumulation required for flower transition was also determined. High temperature treatment rescued the low flower percentage resulting from short storage duration under natural conditions. In addition, extended high storage temperature was found to increase the flowering percentage of 2-year-old plants, which can be applied in breeding. Narcissus FLOWERING LOCUS T1 (NFT1), a homolog of the Arabidopsis thaliana gene FLOWERING LOCUS T, was isolated in this study. NFT1 tran￾scripts were abundant during flower initiation in mature bulbs and were up-regulated by high temperature. The gen￾etic experiments, coupled with an expression profiling assay, suggest that NFT1 possibly takes part in flower transition control in response to high temperature. Keywords: Flower initiation Narcissus tazetta var. chinensis NFT1 Temperature. Abbreviations: CO, CONSTANS; FD, Flowering Locus D, FLC, FLOWERING LOCUS C; FT, FLOWERING LOCUS T; qRT-PCR, quantitative real-time PCR; RACE, rapid ampli- fication of cDNA ednds; SEM, scanning electron microscopy; SM, shoot meristem; SOC1, SUPPRESSOR OF OVEREX￾PRESSION OF CONSTANS1; TFL1, TERMINAL FLOWER 1; WT, wild type. The nucleotide sequence of NFT1 reported in this paper has been submitted to NCBI under accession numbers JX316221 for cDNA and JX316222 for genomic DNA. Introduction Timing of transition to flowering in higher plants is controlled through environmental and endogenous cues. Genetic and mo￾lecular studies in the model plant Arabidopsis thaliana character￾ize a complex network of genetic pathways that regulate flowering (Amasino and Michaels 2010). Vernalization, ambient temperature and photoperiod pathways regulate flowering in response to environmental cues, whereas autonomous, gibberel￾lin and development stage pathways regulate flowering in re￾sponse to endogenous signals (Samach and Wigge 2005, Kobayashi and Weigel 2007, Farrona et al. 2008, Turck et al. 2008, Kim et al. 2009, Mutasa-Gottgens and Hedden 2009, Wang et al. 2009a, Amasino and Michaels 2010). Several key com￾ponent genes involved in these pathways have orthologs in a wide variety of plants, including other monocots and perennials (Amasino 2010). Arabidopsis Flowering Locus T (FT) protein is now widely accepted as a mobile florigen (Corbesier et al. 2007, Giakountis and Coupland 2008). FT is activated in the leaf in response to an inductive photoperiod, and subsequently moves to the shoot apex. FT interacts with the product of Flowering Locus D (FD), a bZIP protein, at the vegetative shoot apex, and then activates transcription of floral meristem genes to start the flowering process (Abe et al. 2005, Wigge et al. 2005). FT orthologs have been discovered in several plant species (Bohlenius et al. 2006, Yan et al. 2006, Faure et al. 2007, Gyllenstrand et al. 2007, Hayama et al. 2007, Danilevskaya et al. 2008, Colasanti and Coneva 2009, Hou and Yang 2009, Kikuchi et al. 2009, Komiya et al. 2009, Blackman et al. 2010, Kong et al. 2010). Seasonal temperature changes elicit seasonal flowering re￾sponses that allow the synchronization of flowering with opti￾mal conditions (King and Heide 2009, Hemming and Trevaskis 2011). Several plant species from temperate regions use cold Plant Cell Physiol. 54(2): 270–281 (2013) doi:10.1093/pcp/pcs181, available online at www.pcp.oxfordjournals.org ! The Author 2013. Published by Oxford University Press on behalf of Japanese Society of Plant Physiologists. All rights reserved. For permissions, please email: journals.permissions@oup.com 270 Plant Cell Physiol. 54(2): 270–281 (2013) doi:10.1093/pcp/pcs181 ! The Author 2013. Regular Paper at East China Normal University on June 3, 2013 http://pcp.oxfordjournals.org/ Downloaded from