Abstract
Evidence supporting nitric oxide (NO) as a mediator of plant biochemistry continues to grow, but its functions at the molecular level remains poorly understood and, in some cases, controversial. To study the role of NO at the transcriptional level in Betula platyphylla cells, we conducted a genome-scale transcriptome analysis of these cells. The transcriptome of untreated birch cells and those treated by sodium nitroprusside (SNP) were analyzed using the Solexa sequencing. Data were collected by sequencing cDNA libraries of birch cells, which had a long period to adapt to the suspension culture conditions before SNP-treated cells and untreated cells were sampled. Among the 34,100 UniGenes detected, BLASTX search revealed that 20,631 genes showed significant (E-values≤10−5) sequence similarity with proteins from the NR-database. Numerous expressed sequence tags (i.e., 1374) were identified as differentially expressed between the 12 h SNP-treated cells and control cells samples: 403 up-regulated and 971 down-regulated. From this, we specifically examined a core set of NO-related transcripts. The altered expression levels of several transcripts, as determined by transcriptome analysis, was confirmed by qRT-PCR. The results of transcriptome analysis, gene expression quantification, the content of triterpenoid and activities of defensive enzymes elucidated NO has a significant effect on many processes including triterpenoid production, carbohydrate metabolism and cell wall biosynthesis.
Highlights
Nitric oxide (NO) is a noxious free radical gas, which in the late 1980s was discovered to exist physiologically in mammalian systems
1 mM was used as the optimal concentration of sodium nitroprusside (SNP) to investigate the effect of exogenous NO in regulating triterpenoid synthesis
The paired-end contig sequences were grouped into scaffolds, which were grouped into tentatively unique genes (TUGs), and reads were used for gap filling
Summary
Nitric oxide (NO) is a noxious free radical gas, which in the late 1980s was discovered to exist physiologically in mammalian systems. The idea that a simple gas could act as a messenger revolutionized the understanding of signal transduction [1, 2]. NO is a key molecule in signal transduction pathways that initiates secondary metabolite biosynthesis in plants [9, 10]. Parani et al (2004) showed that NO modulated the expression of a substantial number of genes at the transcriptional level in Arabidopsis thaliana. Hierarchical clustering revealed 162 genes showing a dose-dependent increase in signal from 0.1 mM SNP to 1.0 mM SNP treatment [11]. The evidence supporting NO as a mediator of plant physiological processes continues to grow, its functions at the molecular level remain poorly understood
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