Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 2/12/2007
Publication Date: 5/24/2007
Citation: Narayanan, N.N., Seman, Z.A., Yan, W., Grusak, M.A. 2007. Expression analysis of metal-related genes in flag leaves of diverse rice germplasm [abstract]. In: Zinc Crops 2007, May 24-26, 2007, Istanbul, Turkey. Presentation GMB-4. Interpretive Summary:
Technical Abstract: Rice, one of the most important food crops, is a poor source of essential minerals such as zinc and iron. Much of the world's micronutrient malnutrition is found in developing countries where rice is the staple food. Therefore, engineering rice plants with enhanced seed mineral concentrations will help to minimize current problems of human micronutrient deficiencies. To assist molecular breeding or transgenic efforts, more information is needed on the molecular players that help mobilize minerals into and throughout the plant, and especially to the developing seeds. In this study, we focused on metal-related gene expression in the flag leaf, because this leaf is the major source of phloem-delivered photoassimilates and mineral nutrients for seeds. Based on an earlier expression study of 36 metal-related genes in rice, we selected eight of the more highly expressed genes for further study. Several diverse rice genotypes, which exhibit different seed concentrations of zinc and iron, were chosen for expression analysis. This allowed us to compare genotypic differences in gene expression with differences in seed mineral concentrations. Transcripts of eight putative metal-related genes (OsIRT1, OsZIP1, OsYSL7, OsYSL8, OsYSL18, OsNRAMP2, OsNRAMP7, and OsNAS1) were detected in all 14 accessions tested. For most of the genes, there were no or only minor differences in gene expression between the accessions. ICP elemental analysis of immature grains showed broad variation in seed mineral concentrations amongst the accessions tested. Preliminary analysis revealed significant correlations between seed Zn concentration and the flag leaf expression of certain genes. Our results suggest that for the eight metal-related genes studied, their protein products contribute to the movement of metals between and within various cellular/subcellular leaf compartments, at least during the stage of grain fill in rice. Correlations between seed Zn concentration and the expression of certain genes implies that a mechanistic link between flag leaf processes and seed Zn delivery can be deciphered, and may lead to new strategies for enhancing the concentration of Zn in seeds.