Characterization Of Emitted Volatiles And Key Genes In Lilium Longiflorum×Asiatic

Floral scents were the important ornamental characters for Lilium spp.Longiflorum-asiatic hybrids(LA hybrids)integrate the advantages of Longiflorum hybrids and Asiatic hybrids,showing up robust stems and light-fragrance.A desire to understand the biochemical and genetic characterization of the metabolic pathways on fragrance emission of LA hybrids,we combined headspace solid-phase microextraction(HS-SPME),gas chromatography-mass spectrometry(GC-MS)and quantitative real-time technique.Five interspecific Lilium hybrids cultivars were collected to analyze scent emissions.These five cultivars were divided into three levels:non-scented,light-scented,and strong-scented.Three genes of mevalonic acid(MVA)pathway were isolated from LA hybrids by homology cloning.Here are the conclusions1.There were significant differences in the release of floral scent components in five different lily hybrids with different levels of fragrance,and the emitted regulation of terpene compounds was consistent with the degree of perceptible fragrance.From the analysis of volatile compounds,we can conlusion that a total of 37 volatile compounds were identified at different stages of flower development and flower organs in LA hybrids "Freya'.With the flowering of 'Freya',the content of aroma components was gradually increased until the mid-opening reached the maximum,but then decreased gradually.Among four floral tissues,the volatiles content of tepal was highest.Terpenoids were the characteristic fragrance on LA hybrids;Terpene compounds accounted for 35%of the total release,including(Z)-3,7-dimethyl-1,3,6-Octatriene,Caryophyllene and so on2.The expression patterns of MVA pathway enzy me genes(HMGR,AVD,FPPS,and TPS)on different interspecific hybrids lily cultivars were different.Besides,the expression regulation of TPS gene was consistent with the emitted regulation of terpene compounds on the flowering of 'Freya'.It was indicated that TPS gene played a pivotal role in the volatilization of terpene compounds3.We obtained a terpene synthase gene,which was the final step in the MVA pathway,named LlaTPS,in LA hybrids 'Freya'.The full length of the cDNA was 1 799 bp,with an open reading frame of 1764 bp,encoding a total of 587 amino acids.The phylogenetic tree analysis showed that LlaTPS was the closest to the monoterpene synthase of Lilium hybrid cultivar 'Siberia',and belongs to TPSb family.4.LlaFPPS gene was cloned from LA hybrids 'Freya',which can catalyze farnesyl diphosphate(FPP)as precursor for sesquiterpene.The full length of the cDNA was 1072 bp,with an open reading frame of 1056 bp,encoding a total of 351 amino acids.The phylogenetic tree analysis showed that LlaFPPS gene encoding protein has close relationship with monocotyledons plant FPPS protein,and far more distant from leguminous plants5.LlaMVD gene was isolated from LA hybrids 'Freya',which is the key gene in the MVA pathway,and GenBank accession number was KX034060.The full length of the cDNA was 1439 bp,with an open reading frame of 1275 bp,encoding a total of 424 amino acids.The phylogenetic tree analyses showed that homology to MVD of Elaeis guineensisIn this study,we analysed the characterization of emitted volatiles and cloned mevalonic acid(MVA)pathway key genes in LA hybrids cultivars.The floral scent release rules of LA hybrids lily were preliminarily explained,which provided the theoretical basis for further exploring the molecular regulation mechanism of lily hybrids.Which provide new insights into molecular mechanisms of fragrance in Lilium,and offer the theoretical basis for generating fragrant in LA hybrids lily.