Transcriptome analysis of the tea oil camellia (Camellia oleifera) reveals candidate drought stress genes

Abstract

BackgroundThe tea-oil camellia (Camellia oleifera) is the most important oil plant in southern China, and has a strong resistance to drought and barren soil. Understanding the molecular mechanisms of drought tolerance would greatly promote its cultivation and molecular breeding.ResultsIn total, we obtained 76,585 unigenes with an average length of 810 bp and an N50 of 1,092 bp. We mapped all the unigenes to the NCBI ‘nr’ (non-redundant), SwissProt, KEGG, and clusters of orthologous groups (COG) databases, where 52,531 (68.6%) unigenes were functionally annotated. According to the annotation, 46,171 (60.8%) unigenes belong to 338 KEGG pathways. We identified a series of unigenes that are related to the synthesis and regulation of abscisic acid (ABA), the activity of protective enzymes, vitamin B6 metabolism, the metabolism of osmolytes, and pathways related to the biosynthesis of secondary metabolites. After exposed to drought for 12 hours, the number of differentially-expressed genes (DEGs) between treated plants and control plants increased in the G4 cultivar, while there was no significant increase in the drought-tolerant C3 cultivar. DEGs associated with drought stress responsive pathways were identified by KEGG pathway enrichment analysis. Moreover, we found 789 DEGs related to transcription factors. Finally, according to the results of qRT-PCR, the expression levels of the 20 unigenes tested were consistent with the results of next-generation sequencing.ConclusionsIn the present study, we identified a large set of cDNA unigenes from C. oleifera annotated using public databases. Further studies of DEGs involved in metabolic pathways related to drought stress and transcription will facilitate the discovery of novel genes involved in resistance to drought stress in this commercially important plant.

Transcriptome sequencing of okra (Abelmoschus esculentus L. Moench) uncovers differently expressed genes responding to drought stress

“…This tendency implies that the higher the degree of drought, the more obvious the effect on gene expression in plants. Similar results were also reported on other plants, such as Camellia oleifera (Dong et al 2017;Xia et al 2014) and Cicer arietinum L. (Mahdavi et al 2018). According to the GO analysis, most of the DEGs were involved in ''integral component of membrane'' ''oxidation-reduction process'', ''metal ion binding'' and ''DNA binding'' from the seven pairs mentioned earlier.…”

“…Several studies (Agarwal et al 2016;Yoshida et al 2015;Liu et al 2016) have reported that TFs were considered to have vital roles in accommodating and resisting drought conditions. We identified abundant TFs belonging to the bHLH (413), MYB (288), MYB-like (269), C2H2 (255), and bZIP (217) families, which is consistent with reports on kabuli chickpea (Cicer arietinum L.) (Mahdavi et al 2018) and tea oil camellia (Camellia oleifera) (Dong et al 2017). Following this, we would like to select several key TFs as candidates for functional verification.…”

“…We also found that 3679 unigenes were mapped to ''environmental information processing'' based on the KEGG pathway. Among these, 3188 unigenes were related to ''signal transduction'', implying that signal transduction processing may affect plants in response to adverse environmental stress (Dong et al 2017).…”

Identification and evaluation of reliable reference genes for quantitative real-time PCR analysis in tea plants under differential biotic stresses

“…Normalizing results with one or more appropriate internal RGs is a simple and popular method for controlling error in qRT-PCR assays. To date, a few housekeeping genes have been rigorously identified and used as RGs in tea plants under abiotic stresses, such as cold, barrenness, drought, photoperiod and exogenous application of plant hormones (auxin, ABA, GA, IAA, MeJA and SA) 25,26,28,[32][33][34] , leaf developmental stages and even different organs 26,35 . These results demonstrate that identifying appropriate RGs for target gene expression analysis under different experimental conditions is an essential prerequisite for developing a qPCR assay of tea plants.…”

Different Nitrate and Ammonium Ratios Affect Growth and Physiological Characteristics of Camellia oleifera Abel. Seedlings

“…Its fruit contains high-quality oil, commonly known as tea oil or camellia oil, which has 82%-84% unsaturated fatty acids, 68%-77% monounsaturated fatty acids, 67.7%-76.7% oleic acid, and 7%-14% polyunsaturated acid. The composition is similar to that of olive oil [2], hence it is called eastern olive oil [3]. Tea oil has also been widely used for cosmetic and medicinal purposes [4].…”