SummaryMycorrhizae are symbioses between soil fungi and roots, with substantial modifications of the cells of both partners, Thus, host cells colonized by mycorrhizal fungi may express otherwise inactive genes. Here it is demonstrated that two arbuscular mycorrhizal (AM) fungi, Glomus versiforme and Gigaspora margarita, cause the transcriptional activation of a gene coding for a-tubulin in the colonized cells of maize and transgenic tobacco roots. Tobacco plants transformed with a construct containing the maize TubG3 gene promoter fused upstream from the bacterial GUS gene showed an intense GUS activity only in meristematic regions. When colonized by G. margarita, GUS activity was detected in the cortical root cells containing fungal arbuscules. No GUS activity was found in root cells when transformants carrying TubG 1 promoter were used, nor when Tub~ 3 transformants were colonized by ericoid mycorrhizal fungi, leading to a non-specific interaction. Activation of the TubG 3 appears to be specific to the gene and to the appropriate interaction. Further evidence that fully differentiated host tissues re-activate the TubG 3 gene following colonization by AM fungi also comes from accumulation of the corresponding transcripts in maize root cells containing arbuscules.
In the past few years many alpha- and beta-tubulin genes of different organisms have been cloned and studied, and in most systems studied they constitute multigene families. In plants, most studies have been done in Arabidopsis thaliana and Zea mays. In this paper, the study of mRNA accumulation by in situ hybridization and the activity of three maize alpha-tubulin gene promoters (tua1, tua2 and tua3) in transgenic tobacco plants are described. In maize, the expression of these three tubulin isotypes differ in the root and shoot apex and is associated with different groups of cells throughout the distinct stages of cell differentiation. In transgenic tobacco plants the promoters of the genes, fused to the uidA reporter gene (GUS), direct expression to the same tissues observed by in situ hybridization experiments. The tua1 promoter is mainly active in cortex-producing meristematic cells and in pollen, whereas tua3 is active in cells which are differentiating to form vascular bundles in the root and shoot apices. The accumulation of tua2 mRNA is detected by RNA blot in a similar form as tua1, but at a very much low level. In situ hybridization indicates that the tua2 mRNA specifically accumulates in the maize root epidermis. No GUS staining was detected in transgenic tobacco plants with the tua2 promoter. The difference in expression of the specific genes may be linked to processes where microtubules have different functions, suggesting that in plants, as in animals, there are differences in the function of the tubulin isotypes.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
customersupport@researchsolutions.com
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.