Abstract
Genome-wide expression studies on nodulation have varied in their scale from entire root systems to dissected nodules or root sections containing nodule primordia (NP). More recently efforts have focused on developing methods for isolation of root hairs from infected plants and the application of laser-capture microdissection technology to nodules. Here we analyze two published data sets to identify a core set of infection genes that are expressed in the nodule and in root hairs during infection. Among the genes identified were those encoding phenylpropanoid biosynthesis enzymes including Chalcone-O-Methyltransferase which is required for the production of the potent Nod gene inducer 4′,4-dihydroxy-2-methoxychalcone. A promoter-GUS analysis in transgenic hairy roots for two genes encoding Chalcone-O-Methyltransferase isoforms revealed their expression in rhizobially infected root hairs and the nodule infection zone but not in the nitrogen fixation zone. We also describe a group of Rhizobially Induced Peroxidases whose expression overlaps with the production of superoxide in rhizobially infected root hairs and in nodules and roots. Finally, we identify a cohort of co-regulated transcription factors as candidate regulators of these processes.
Highlights
Most legumes are able to interact with soil bacteria called rhizobia to form special root structures called nodules within which the bacteria are able to fix atmospheric nitrogen, a process which is fueled by host photosynthate
To identify genes common to infection thread formation in these two cell types we compared genes that were induced either by rhizobia or by purified Nod factors in root hairs with the genes expressed in different nodule zones (Roux et al, 2014)
The large family genes encoding for nodule-specific cysteine-rich (NCR) peptides, which are highly expressed in the nodule but are not expressed in root hairs, are thereby excluded
Summary
Most legumes are able to interact with soil bacteria called rhizobia to form special root structures called nodules within which the bacteria are able to fix atmospheric nitrogen, a process which is fueled by host photosynthate. In Medicago truncatula, as with many legumes, the rhizobia infects the host root by colonizing special intracellular tubular invaginations called infection threads that form first in root hairs and later in mature nodules. This process begins with rhizobial attachment near the tip of growing root hairs which curl and entrap a rhizobial microcolony in an infection pocket, called an infection focus. While maturing the nodule forms several developmental zones: an apical
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
