Studies On Development And Terpenoid Metabolism Of Tobacco Trichome

To resolve the development and terpenoid metabolism of the tobacco leaf trichomes,microscopic observation, RT-PCR and GC/MS analysis technology had been used to analysis thedifference between the secretory and non-secreting glandular hairs in the aspect of morphology,gene expression and terpenoid metabolism. Then discussed the trichomes defense reaction, whichinduced by MeJA. And its morphogenesis metabolism and metabolic variation under differentcondition of light by exposuring to light quality, light intensity, photoperiod and UV-B radiation.The main results were as follows:1. Different types of tobacco glandular hairs in morphological structure, gene expression,metabolism and aphid resistance has significant difference. T.I1068owns long head glandularhairs, which were composed by multiple cytoplasmic dense and rich in chloroplast cells. Inaddition, a secretion cystic packing its head. The glandular hairs of T.I1406were similar as T.I1068, but they hav not secretion cystic above the head. In comparison, I35glandular hairs are nogland head to protect hair, thin cytoplasm and lack of chloroplast. Chemical analysis of leafshowed that T.I1068had the highest leaf secretion component and content, T.I1406hold secondplace, I35was the minimum, the differences were in content of CBT diterpenoid compounds. Theresult of RT-PCR showed that the in trichomes of T.I1068was strongest, but T.I1406could notcompose and secret CBT-ols. The glandular hairs of I35had weak diterpeniod but strongsesquiterpenes metabolism. Aphids preference analysis showed that the resistance to aphids of T.I1068was stronger than T.I1406and I35, and this also demonstrated that secretions of trichomesplayed a great role in aphids defense.2. This experiment sprayed methyl jasmonate (MeJA) on the tobacco seedling, and studied on theleaf trichome density, type, chemical composition, gene expression and resistance response ofaphid to treatment. Scanning electron microscope observation found that, MeJA made the newtrichome density of tobacco plants increased, especially the long trichomes; GC/MS showed that,MeJA treatment elevated leaf surface chemical substances, which had reached the maximum valueat the7th day; cembranoids compounds, which secreted only by trichomes, is the main componentof foliar chemistry secretions, its contented with the biggest MeJA changes; and more aphidsselected the leaves which sprayed without MeJA. But the analysis of gene expression showed that MeJA did not alter the terpenoid metabolism of trichomes, which suggested that there maybe acomplex posttranscriptional regulation mechanism in tobacco glandular hairs.3. Lighting conditions made a great influence to the glandular hair morphology and terpenoidmetabolism.(1) Different light qualities. Trichome density under red light was significantly lowerthan under the white light and blue light, and the difference is mainly caused by the long handleglandular hairs. Under the white light, CBT secretions compounds of glandular hairs was thehighest. But gene expression analysis showed that there were no difference on diterpenemetabolism between the three kinds of light quality.(2) Different light intensity. Under mediumlight level(9610Lx), the highest density of leaf trichomes with developed head cells werediscovered. Although stalk cells of trichomes grew vigrously under both high(15380Lx) and weaklighr level(7500Lx), the development and chlorophyll biolosynthesis of head cells were clearlysuppressed. CBT-ol and CBT-diol, the main component of trichome secretion, accumulated muchmore greatly in medium light level, but the related gene, DXR, CBT and CYP71D16, expressedmore actively in transcript level in trichomes growing in weak light level. This suggested thatmore complicated post-transcrip regulation mechanism was existed in substance metabilism oftobacco trichome.(3) Different photoperiod. Long-day plants had bigger trichome density,moderate size and more secretion compared with the short-day plants, and the latter were weakeron the gene expression intensity of diterpene anabolism, but stronger on metabilism.(4) UV-Bradiation. UV-B treatment increase the density of glandular hairs, following with that, secretion oftrichiomes were increased, and CBT significantly increased. The diterpene synthesis related genesexpression of glandular hairs continued to strengthen after treatment. Sesquiterpenes metabilismwere first got strong then decrease rapidly with time.