Developmental regulation of genes for microsome and plastid ω-3 fatty acid desaturases in wheat (Triticum aestivum L.)

omega-3 fatty acid desaturase is responsible for the production of alpha-Iinolenic acid, which is a major fatty acid constituent of membrane lipids in higher plants. In this study, the developmental regulation of the expression of two genes, TaFAD3 and TaFAD7, which respectively encode the microsome and plastid omega-3 fatty acid desaturases in wheat, was analyzed by in situ hybridization. The transcript of TaFAD3 was abundant in the apical meristems of both shoot and root, the leaf primordium, the leaf basal intercalary meristem, and the root vascular tissues. The level of TaFAD3 mRNA was also high in embryos developing after flowering. In mature embryos, however, it was low, whereas in germinating embryos it was once again high. These results suggest that the TaFAD3 mRNA is accumulated at a high level in cells that have an ability to proliferate, In contrast, the TaFAD7 mRNA level was very low in the shoot apical meristem, leaf primordium and leaf basal intercalary meristem, but a large accumulation of TaFAD7 mRNA was found in green tissues, suggesting that the accumulation of this mRNA is associated with chloroplast development. Although the spatial distribution patterns of TaFAD3 and TaFAD7 mRNAs clearly differed, the enhanced accumulation of the TaFAD3 and TaFAD7 mRNAs was linked with the active membrane biogenesis required for cell division and with the development of the thylakoid system in plastids, respectively.