Abstract: Nitric oxide (NO) is an important signaling molecule with diverse physiological functions in plants. NO can break dormancy of seeds, and promote seeds germination under various stresses and normal growth conditions. In this report, treatment with 0.5 mmol L^-1 sodium nitroprusside (SNP) promoted seeds germination by increasing β-amylase activity, while the application of α-cyclodextrin, a specific inhibitor of β-amylase, could apparently inhibit the process induced by SNP. Semi-quantitative RT-PCR analysis indicated that the application of SNP induced the free β-amylase activity, and up-regulated β-amylase transcript. West-ern-blotting result showed that SNP increased the protein level of β-amylase, whereas the cPTIO (a specific scavenger of NO) and actinomycin-D (a transcriptional inhibitor) reversed changes in transcriptional and the protein levels mentioned above. Subcellular localization studies of proteins via immunoelectron microscopy technique illustrated that SNP could increase the quantity of β-amylase which was predominantly located in protein storage vacuole, and adhered to starch granules. The above results suggest that SNP might not only enhance the activity of free β-amylase, but also induce the β-amylase synthesis de novo at the early stage of wheat seed germination.

Key words: Nitric oxide, β-amylase, Transcriptional regulation, Subcellular localization, Wheat seeds