## 2 Results
### Transcriptomes Sequencing, Assembly, and Annotation  
In order to decipher the metabolic genes or mechanism underlying VOC biosynthesis, we have combined the next-generation and third-generation sequencing techniques to get full-length transcripts of peony. Hence, the _P. lactiffora_ cv. Zifengyu flowers at the budding, half-, and fully open flowering stages were chosen to construct nine cDNA libraries (three replicates for each stage) for Illumina sequencing. After the assembly of transcriptomes from three flowering stages, 34.32 Gb of clean data was obtained. Within this dataset, a total of 311,155 unigenes were identified, averaging about 133.99 million reads (Table 1). Among these unigenes, 26,724 were characterized by a length greater than 1 kb, suggesting a substantial portion of the transcriptome containing longer sequences. Moreover, the quality of the data was assessed, revealing a Q30 score of 93.89%, indicating high accuracy in base calling and sequencing reliability. Overall, the annotated genes generated from Illumina RNA sequencing were 44,307 (Table 1). Furthermore, samples from the three flowering stages were individually analyzed (Table 2). After the transcriptome assembly of the budding stage sample, 134.3 million clean reads from 179.95 million total raw reads were obtained, with Q20 and Q30 scores of 97.91% and 93.41%, respectively. From the half-open flowering stage, 133.09 million clean reads from 165.95 million total raw reads were generated, with Q20 and Q30 scores of 97.88% and 92.69%, respectively. Similarly, from the fully open floral sample, 134.59 million clean reads from 197.485 million total raw reads were obtained, with Q20 and Q30 scores of 98.23% and 93.61%, respectively. Notably, the clean read ratio was computed by dividing filtered reads with the total number of total reads obtained by sequencing. Overall, the clean read ratio, representing the proportion of high-quality sequencing reads, was found to be 79.63%, 80.79%, and 70.53% for the budding stage, half-open, and fully open flowering samples, respectively (Table 2). The full-length transcriptome analysis of the _P. lactiffora_ cv. Zifengyu pooled sample from three flowering stages was performed using single-molecule real-time (SMRT) sequencing on the PacBio Sequel platform (Table 3). After assembly, 1,799,987 total polymerase reads and 37,444,331 subreads were obtained. The 1,625,074 ROIs (total reads of inserts) were classified into 4,064,073 FLNC (full-length non-chimeric) which had the 5\({}^{\prime}\) and 3\({}^{\prime}\) barcoded primers and the poly (A) tail. After error correction and combining library clusters, redundancy was removed, and these processes yielded 3,884,048 isoforms with an average sequence length of 1099 bp and a mean quality of 0.99. Notably, after redundancy, 493,042 final isoforms were obtained, with a total length of 610,095,296, a characteristic minimum and maximum length of 200 and 30,833, and an N50 and sequence GC content of 1618 and 41.62%, respectively. To predict the coding regions, the SwissProt database was then subjected to BLAST and Hmmscan algorithms to search for matches to Pfam domains. After this process, 295,835 coding DNA sequences (CDSs) were obtained (Table 3). Subsequently, the quality of assembled transcripts and annotation completeness were assessed \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Clean Data** & \begin{tabular}{c} **Mean Reads** \\ **(10\({}^{3}\))** \\ \end{tabular} & \begin{tabular}{c} **Total** \\ **Unigenes** \\ \end{tabular} & \
\begin{tabular}{c} **Unigenes** \\ **(Length \textgreater{} 1 kb)** \\ \end{tabular} &
\begin{tabular}{c} **Q30** \\ **Annotation** \\ \end{tabular} \\ \hline
34.32 Gb & 133.99 & 311,155 & 26,724 & 0.9389 & 44,307 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Illumina sequence clean data from _P. lactiffora_ floral sample.