Abstract
BackgroundLeaf trichomes of Nicotiana tabacum are distinguished by their large size, high density, and superior secretion ability. They contribute to plant defense response against biotic and abiotic stress, and also influence leaf aroma and smoke flavor. However, there is limited genomic information about trichomes of this non-model plant species.ResultsWe have characterized Nicotiana tabacum leaf trichome gene expression using two approaches. In the first, a trichome cDNA library was randomly sequenced, and 2831 unique genes were obtained. The most highly abundant transcript was ribulose bisphosphate carboxylase (RuBisCO). Among the related sequences, most encoded enzymes involved in primary metabolism. Secondary metabolism related genes, such as isoprenoid and flavonoid biosynthesis-related, were also identified. In the second approach, a cDNA microarray prepared from these 2831 clones was used to compare gene expression levels in trichome and leaf. There were 438 differentially expressed genes between trichome and leaves-minus-trichomes. Of these, 207 highly expressed genes in tobacco trichomes were enriched in second metabolic processes, defense responses, and the metabolism regulation categories. The expression of selected unigenes was confirmed by semi-quantitative RT-PCR analysis, some of which were specifically expressed in trichomes.ConclusionThe expression feature of leaf trichomes in Nicotiana tabacum indicates their metabolic activity and potential importance in stress resistance. Sequences predominantly expressed in trichomes will facilitate gene-mining and metabolism control of plant trichome.
Highlights
Leaf trichomes of Nicotiana tabacum are distinguished by their large size, high density, and superior secretion ability
Only limited genomic information on tobacco trichome is available in scattered databases
Combining large-scale random sequencing with gene expression analysis has provided a unique and comprehensive overview of transcription related to key metabolic pathways in tobacco trichomes
Summary
Leaf trichomes of Nicotiana tabacum are distinguished by their large size, high density, and superior secretion ability. They contribute to plant defense response against biotic and abiotic stress, and influence leaf aroma and smoke flavor. There is limited genomic information about trichomes of this non-model plant species. Plant trichomes frequently function as the first line of defense against biotic and abiotic stresses by space hindrance [1]. Some plant species bear glandular trichomes that secrete a series of lipophilic substances and proteins, and are distinguished for their medicinal, culinary, fragrant and insecticidal properties. Limited information about metabolism and secretion can be obtained from these expression differ in plant species, being closely related to morphology, structure, development and metabolism features
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