Abstract
Elimination of Cd via the production of Ca-containing grains at the top of leaf trichomes is a potent detoxification mechanism in tobacco (Nicotiana tabacum L. cv. Xanthi) plant. The synchrotron-radiation based micro X-ray diffraction (micro-XRD), and micro X-ray absorption near edge structure (micro-XANES) spectroscopy were used to characterize Cd-containing grains. Most of the grains were Cd-substituted calcite or vatelite. Cys-rich Pathogenesis-related (PR) proteins were scored highly in EST libraries of tobacco glandular leaf trichomes. RT-PCR demonstrated that they are expressed dominant or specific expression in trichomes, indicating that they are candidates for heavy metal cheaters. The expression of genes for the class 5 PR-proteins, osmotin and thaumatin-like protein, were increased during Cd treatment in leaves and trichomes. The confocal laser-scanning microscopy visualized the glutathione accumulation in top cells of the trichomes, and the dominant expression of glutathione peroxidase was detected in trichomes. Our results showed the tobacco trichome is a biologically active and stress-responsive tissue.
