Large-scale analysis of gene expression profiles during early stages of root nodule formation in a model legume, Lotus japonicus.
Gene expression profiles during early stages of formation of symbiotic nitrogen-fixing nodules in a model legume Lotus japonicus were analyzed by means of a cDNA array of 18,144 non-redundant expressed sequence tags (ESTs) isolated from L. japonicus. Expression of a total of 1,076 genes was significantly accelerated during the successive stages that represent infection of Mesorhizobium loti, nodule primordium initiation, nodule organogenesis, and the onset of nitrogen fixation. These include 32 nodulin and nodulinhomolog genes as well as a number of genes involved in the catabolism of photosynthates and assimilation of fixed nitrogen that were previously known to be abundantly expressed in root nodules of many legumes. We also identified a large number of novel nodule-specific or enhanced genes, which include genes involved in many cellular processes such as membrane transport, defense responses, phytohormone synthesis and responses, signal transduction, cell wall synthesis, and transcriptional regulation. Notably, our data indicate that the gene expression profile in early steps of Rhizobium-legume interactions is considerably different from that in subsequent stages of nodule development. A number of genes involved in the defense responses to pathogens and other stresses were induced abundantly in the infection process, but their expression was suppressed during subsequent nodule formation. The results provide a comprehensive data source for investigation of molecular mechanisms underlying nodulation and symbiotic nitrogen fixation.
Kouchi
Hiroshi
H
National Institute of Agrobiological Sciences, Tsukuba, Ibaraki 305-8602, Japan. kouchih@nias.affrc.go.jp
Shimomura
Kenshiro
K
Hata
Shingo
S
Hirota
Atsuko
A
Wu
Guo-Jiang
GJ
Kumagai
Hirotaka
H
Tajima
Shigeyuki
S
Suganuma
Norio
N
Suzuki
Akihiro
A
Aoki
Toshio
T
Hayashi
Makoto
M
Yokoyama
Tadashi
T
Ohyama
Takuji
T
Asamizu
Erika
E
Kuwata
Chikara
C
Shibata
Daisuke
D
Tabata
Satoshi
S
D015152:Blotting, Northern; D002473:Cell Wall / Q000378:metabolism; D018076:DNA, Complementary / Q000235:genetics; D020224:Expressed Sequence Tags; D020869:Gene Expression Profiling; D018507:Gene Expression Regulation, Developmental; D018506:Gene Expression Regulation, Plant; D005798:Genes, Bacterial; D000070116:Lotus / Q000166:cytology / Q000235:genetics* / Q000254:growth & development; D008565:Membrane Proteins / Q000235:genetics; D009586:Nitrogen Fixation / Q000235:genetics*; D020411:Oligonucleotide Array Sequence Analysis; D010937:Plant Growth Regulators / Q000096:biosynthesis; D010940:Plant Proteins / Q000235:genetics; D018517:Plant Roots / Q000378:metabolism; D016133:Polymerase Chain Reaction; D018749:RNA, Plant / Q000235:genetics; D012230:Rhizobiaceae / Q000502:physiology; D015398:Signal Transduction / Q000235:genetics; D013559:Symbiosis; D014158:Transcription, Genetic / Q000235:genetics
D018076:DNA, Complementary; D008565:Membrane Proteins; D010937:Plant Growth Regulators; D010940:Plant Proteins; D018749:RNA, Plant; C045625:nodulin