Expression of symbiotic and nonsymbiotic globin genes responding to microsymbionts on Lotus japonicus.
Leguminous plants have both symbiotic and nonsymbiotic hemoglobin (sym- and nonsym-Hb) genes. Three symbiotic (LjLb1, 2, 3) and one nonsymbiotic (LjNSG1) Hb genes were isolated from a genomic library of Lotus japonicus MG20 Miyakojima. Two motif sequences (AAAGAT and CTCTT) critical for nodule specific expression were conserved on the 5'-upstream sequence of LjLb1, 2 and 3. The 5'-upstream region of LjNSG1 contained the sequence consensus for nonsym-Hb. RT-PCR with specific primer sets for each LjLb gene showed that all the sym-Hb genes (LjLb1, 2, 3) were expressed specifically and strongly in root nodules. The expression of LjLb1, 2 and 3 could not be detected in root, leaf or stem of a mature plant, whereas low level expression was detected in seedlings by RT-PCR. This suggests that sym-Hbs may have another unknown function besides being oxygen transporter for the microsymbiont in symbiotic nitrogen fixation. The expression of LjNSG1, examined with RT-PCR, was detected at low level in root, leaf and stem. The expression of LjNSG1 was enhanced in root nodules, whereas it was repressed in roots colonized by mycorrhizal fungi Glomus sp. R10. The repression of the nonsym-Hb gene was also observed in the roots of Medicago sativa colonized by Glomus sp. R10.
Uchiumi
Toshiki
T
Department of Chemistry and BioScience, Kagoshima University, Kagoshima, 890-0065 Japan. uttan@sci.kagoshima-u.ac.jp
Shimoda
Yoshikazu
Y
Tsuruta
Tomoko
T
Mukoyoshi
Yumi
Y
Suzuki
Akihiro
A
Senoo
Keishi
K
Sato
Shusei
S
Kato
Tomohiko
T
Tabata
Satoshi
S
Higashi
Shiro
S
Abe
Mikiko
M
D001483:Base Sequence; D015139:Blotting, Southern; D018744:DNA, Plant / Q000737:chemistry / Q000235:genetics; D018506:Gene Expression Regulation, Plant; D005914:Globins / Q000235:genetics* / Q000378:metabolism; D006420:Hemeproteins / Q000235:genetics* / Q000378:metabolism; D000070116:Lotus / Q000235:genetics* / Q000382:microbiology; D008969:Molecular Sequence Data; D038821:Mycorrhizae / Q000254:growth & development; D010802:Phylogeny; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D018517:Plant Roots / Q000235:genetics / Q000382:microbiology; D012230:Rhizobiaceae / Q000254:growth & development; D017422:Sequence Analysis, DNA; D012689:Sequence Homology, Nucleic Acid; D013559:Symbiosis / Q000235:genetics* / Q000502:physiology
D018744:DNA, Plant; D006420:Hemeproteins; D010940:Plant Proteins; D005914:Globins