## 2 Transcriptomics  
Transcriptomics provide information on the occurrence and relative abundance of RNA transcripts, indicating the active components within cell [12]. Serial analysis of gene expression and microarrays have been applied to many model systems, aiming to study the predominantly expressed genes in stem cells. The resulting sequence typically reads 30 to 400 base pairs in length, commonly aligned to a reference genome and assessed for quality, depending on DNA-sequencing technology used. Data processing and quality assessment tools generally provide diagnostic visualizations [13].  
Using the Illumina sequence analytical method, [PERSON], et al. [14] obtained about 57.35 million RNA-Seq reads pooled into 216.831 transcripts, with an average length of 356 bp and an N50 of 529 bp. Analysis of pathways showed that both carbohydrate metabolism and calcium signaling pathways could play an important role in _C. sinensis_ cold stress responses. The transcriptome from poly (A) + RNA of _C. sinensis_ was analyzed at an unprecedented depth (2.59 gigabase pairs) by [PERSON] et al. [15] in order to identify most of the genes associated with flavonoid, theanine, and caffeine biosynthetic pathways. [PERSON] et al. [16] analyzed a floral transcriptome of _C. sinensis_ and assembled 26.9 million clean readings in 75.531 unigenes, averaging 402 bp. Both _C. sinensis_ transcriptome information and genetic maps provide a valuable basis for molecular biology investigations, such as functional gene isolation, quantitative trait loci mapping, and marker-assisted selection breeding in this important species.  
MicroRNAs (miRNAs) are small RNAs endogenous that have an important role in plant development and growth, as well as in stress responses [17]. _C. sinensis_ has 47.452 expressed sequence tags (EST) available and 14 new _C. sinensis_ miRNAs were identified by EST analysis. These miRNAs target 51 mRNAs, which can act as transcription factors and participate in several cell process such as oxidation-reduction, transmembrane transport, signal transduction, and stress response. Indeed, gene ontology analysis based on these targets suggested that 37 biological processes were involved, and the Kyoto Encyclopedia of Genes and Genomes pathway enrichment analysis inferred that the identified miRNAs participate in 13 metabolic networks. [PERSON] et al. [18] applied an RNA isolation protocol that used guanidine hydrochloride on lyophilized leaves of _C. sinensis_. Thus, the use of lyophilized tissues for RNA isolation from tea leaves was explored. High RNA yields (~500 ug/g dry weight of leaf tissue) were obtained, and RNA was suitable for Northern blotting, reverse transcription, and microarray analysis. Therefore, it was revealed that RNA obtained from lyophilized leaf has high quality, and is undegraded and useful for all downstream applications [18]. In a comparative transcriptome analysis by RNA-sequencing, it was elucidated that exogenous calcium increased _C. sinensis_ thermotolerance [19].  
Figure 2: Role of endophytic bacteria and environmental stress on primary and secondary metabolites that affect antioxidant and antimicrobial activities of _Camelia sinensis_, and how omics technologies allow understanding of these biological phenomena.