Investigation of the metabolome and the transcriptome of pollen of lily (Lilium longiflorum) gave a comprehensive overview of metabolic pathways active during pollen germination and tube growth. More than 100 different metabolites were determined simultaneously by gas chromatography coupled to mass spectrometry, and expressed genes of selected metabolic pathways were identified by next-generation sequencing of lily pollen transcripts. The time-dependent changes in metabolite abundances, as well as the changes after inhibition of the mitochondrial electron transport chain, revealed a fast and dynamic adaption of the metabolic pathways in the range of minutes. The metabolic state prior to pollen germination differed clearly from the metabolic state during pollen tube growth, as indicated by principal component analysis of all detected metabolites and by detailed observation of individual metabolites. For instance, the amount of sucrose increased during the first 60 minutes of pollen culture but decreased during tube growth, while glucose and fructose showed the opposite behavior. Glycolysis, tricarbonic acid cycle, glyoxylate cycle, starch, and fatty acid degradation were activated, providing energy during pollen germination and tube growth. Inhibition of the mitochondrial electron transport chain by antimycin A resulted in an immediate production of ethanol and a fast rearrangement of metabolic pathways, which correlated with changes in the amounts of the majority of identified metabolites, e.g. a rapid increase in γ-aminobutyric acid indicated the activation of a γ-aminobutyric acid shunt in the tricarbonic acid cycle, while ethanol fermentation compensated the reduced ATP production after inhibition of the oxidative phosphorylation.

The new transcriptomes provided comprehensive sequence profiling data of transcriptomic variation during vernalization in Lily Asiatic Hybrids 'Tiny ghost'. A number of 52,277,184 sequencing raw reads totaling 5.11 Gbp of the chilling treatment (4 °C) sample and 39,466,176 sequencing raw reads totaling 3.85 Gbp of room temperature control (25 °C) sample were assembled de novo into 68,718 unigenes with a mean length of 984 bp, and a total of 33,208 (45.6%) unigenes were annotated by using public protein databases with a cut-off E value about 10(-5). There are 6,153 unigenes of which were assigned to specific metabolic pathways by the Kyoto encyclopedia of genes and genomes. Gene Ontology analysis of the annotated unigenes revealed that the majority of sequenced genes were associated with signal transduction mechanisms, posttranslational modification, protein turnover and chaperones. In addition, the genes expression levels were compared just after vernalization completion between the cold treatment and room temperature control. There are 68,116 unigenes were differentially expressed, and hierarchical clustering analysis arranged 7,301 significantly differentially-expressed unigenes into 56 groups. Six genes related to the vernalization were selected to confirm their expression levels by using quantitative real-time polymerase chain reaction. Furthermore, typical vernalization unigenes VRN1 and VRN2 were identified, and also some vernalization-associated unigenes, such as CBF, SOC, TaAGL, AP2, LEA, LIM et al. were also annotated in the present study. As for VRN1 and VRN2, their expressions were consistent with some previous related studies. Also, this was the first time the vernalization genes VRN1 and VRN2 were founded in lily. According to the results of the present studies, we predicted that they would play an important role during vernalization in Lily Asiatic Hybrids; these data provided the foundation for the future studies of metabolism during vernalization of Asiatic lily.