Open AccessNodulation Studies in the Model Legume Medicago truncatula: Advantages of Using the Constitutive EF1α Promoter and Limitations in Detecting Fluorescent Reporter Proteins in Nodule Tissues
Author(s) -
MarieChristine Auriac,
A.C.J. Timmers
Publication year - 2007
Publication title -
molecular plant-microbe interactions
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.565
H-Index - 153
eISSN - 1943-7706
pISSN - 0894-0282
DOI - 10.1094/mpmi-20-9-1040
Subject(s) - medicago truncatula , biology , green fluorescent protein , meristem , nodule (geology) , root nodule , cauliflower mosaic virus , reporter gene , microbiology and biotechnology , arabidopsis thaliana , fluorescence , gene , gene expression , nitrogen fixation , genetics , genetically modified crops , symbiosis , transgene , paleontology , bacteria , mutant , physics , quantum mechanics
The Cauliflower mosaic virus 35S promoter currently is being used in RNAi-based approaches for attenuating host gene expression during legume root nodule development and also for the expression of fluorescent reporters in nodule tissues. In this study, we have evaluated the expression of this promoter in the indeterminate nodules of the model plant Medicago truncatula. Our results clearly show that the 35S promoter is inactive in both the nodule meristem and in bacteroid-containing cells of the nodules. On the other hand, the Arabidopsis thaliana EF1α promoter was found to be strongly expressed both in the nodule meristem and in all nodule-invaded cells. Therefore, we conclude that the constitutive EF1α promoter is far superior for mRNAi or overexpression studies in nodule tissues compared with the commonly used 35S promoter. In addition, our experiments have revealed that the intensity of fluorescent markers such as green fluorescent protein is severely attenuated within invaded cells in the nitrogen-fixation zone of the nodule, most likely by fluorescence quenching. This phenomenon may hinder the use of these tools for live-cell imaging in nodule tissue.