Zhu Ren

RNA Sequencing Analysis Reveals Transcriptomic Variations in Tobacco (Nicotiana tabacum) Leaves Affected by Climate, Soil, and Tillage Factors

The growth and development of plants are sensitive to their surroundings. Although numerous studies have analyzed plant transcriptomic variation, few have quantified the effect of combinations of factors or identified factor-specific effects. In this study, we performed RNA sequencing (RNA-seq) analysis on tobacco leaves derived from 10 treatment combinations of three groups of ecological factors, i.e., climate factors (CFs), soil factors (SFs), and tillage factors (TFs). We detected 4980, 2916, and 1605 differentially expressed genes (DEGs) that were affected by CFs, SFs, and TFs, which included 2703, 768, and 507 specific and 703 common DEGs (simultaneously regulated by CFs, SFs, and TFs), respectively. GO and KEGG enrichment analyses showed that genes involved in abiotic stress responses and secondary metabolic pathways were overrepresented in the common and CF-specific DEGs. In addition, we noted enrichment in CF-specific DEGs related to the circadian rhythm, SF-specific DEGs involved in mineral nutrient absorption and transport, and SF- and TF-specific DEGs associated with photosynthesis. Based on these results, we propose a model that explains how plants adapt to various ecological factors at the transcriptomic level. Additionally, the identified DEGs lay the foundation for future investigations of stress resistance, circadian rhythm and photosynthesis in tobacco.

Identification and quantitation of glycosidically bound aroma compounds in three tobacco types by gas chromatography–mass spectrometry

Glycosidically bound aroma compounds in three different types of tobacco were investigated. After isolation of extracts obtained by Amberlite XAD-2 adsorption and ethyl acetate elution, glycosides were analyzed after enzymatic hydrolysis by gas chromatography-mass spectrometry (GC-MS) or directly after trifluoroacetylated (TFA) derivatization by GC-MS in electron ionization (EI) and negative chemical ionization (NCI) mode. In total 21 bound aglycones were identified by β-glucosidase hydrolysis. These aglycones mainly consisted of C13-norisoprenoids, aromatic components and sesquiterpenoids. Additionally, with the aid of enzymatic hydrolysis, 15 β-d-glucopyranosides and 1 β-d-rutinoside were tentatively identified by TFA derivatization. TFA method was validated by repeatability and successfully employed to analyze different types of tobacco. Principal component analysis (PCA) was carried out on identified glycoside variables to visualize the difference between the tobacco types and the relationship between the glycoside variables and the tobacco types was established.

Comparative transcriptome analysis of tobacco (Nicotiana tabacum) leaves to identify aroma compound-related genes expressed in different cultivated regions.

To identify genes that are differentially expressed in tobacco in response to environmental changes and to decipher the mechanisms by which aromatic carotenoids are formed in tobacco, an Agilent Tobacco Gene Expression microarray was adapted for transcriptome comparison of tobacco leaves derived from three cultivated regions of China, Kaiyang (KY), Weining (WN) and Tianzhu (TZ). A total of 1,005 genes were differentially expressed between leaves derived from KY and TZ, 733 between KY and WN, and 517 between TZ and WN. Genes that were upregulated in leaves from WN and TZ tended to be involved in secondary metabolism pathways, and included several carotenoid pathway genes, e.g., NtPYS, NtPDS, and NtLCYE, whereas those that were down-regulated tended to be involved in the response to temperature and light. The expression of 10 differentially expressed genes (DEGs) was evaluated by real-time quantitative polymerase chain reaction (qRT-PCR) and found to be consistent with the microarray data. Gene Ontology and MapMan analyses indicate that the genes that were differentially expressed among the three cultivated regions were associated with the light reaction of photosystem II, response to stimuli, and secondary metabolism. High-performance liquid chromatography (HPLC) analysis showed that leaves derived from KY had the lowest levels of lutein, β-carotene, and neoxanthin, whereas the total carotenoid content in leaves from TZ was greatest, a finding that could well be explained by the expression patterns of DEGs in the carotenoid pathway. These results may help elucidate the molecular mechanisms underlying environmental adaptation and accumulation of aroma compounds in tobacco.