Identification of a core set of rhizobial infection genes using data from single cell-types.
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.
State Key Laboratory of Agricultural Microbiology, College of Life Science and Technology, Huazhong Agricultural University, Wuhan China.
Da-Song
DS
Chen
John Innes Centre, Department of Cell and Developmental Biology, Norfolk UK.
Cheng-Wu
CW
Liu
John Innes Centre, Department of Cell and Developmental Biology, Norfolk UK.
Sonali
S
Roy
John Innes Centre, Department of Cell and Developmental Biology, Norfolk UK.
Donna
D
Cousins
John Innes Centre, Department of Cell and Developmental Biology, Norfolk UK.
Nicola
N
Stacey
John Innes Centre, Department of Cell and Developmental Biology, Norfolk UK.
Jeremy D
JD
Murray
CCAAT-box; Nod factors; infection threads; infection zone; medicarpin; methoxychalcone; nod genes; nodulation