Hemoglobin LjGlb1-1 is involved in nodulation and regulates the level of nitric oxide in the Lotus japonicus-Mesorhizobium loti symbiosis

TY - JOUR

T1 - Hemoglobin LjGlb1-1 is involved in nodulation and regulates the level of nitric oxide in the Lotus japonicus-Mesorhizobium loti symbiosis

AU - Fukudome, Mitsutake

AU - Calvo-Begueria, Laura

AU - Kado, Tomohiro

AU - Osuki, Ken-ichi

AU - Rubio, Maria Carmen

AU - Murakami, Eiichi

AU - Nagata, Maki

AU - Kucho, Ken-ichi

AU - Sandal, Niels Nørgaard

AU - Stougaard, Jens

AU - Becana, Manuel

AU - Uchiumi, Toshiki

PY - 2016/9/1

Y1 - 2016/9/1

N2 - Leghemoglobins transport and deliver O 2 to the symbiosomes inside legume nodules and are essential for nitrogen fixation. However, the roles of other hemoglobins (Hbs) in the rhizobia-legume symbiosis are unclear. Several Lotus japonicus mutants affecting LjGlb1-1, a non-symbiotic class 1 Hb, have been used to study the function of this protein in symbiosis. Two TILLING alleles with single amino acid substitutions (A102V and E127K) and a LORE1 null allele with a retrotransposon insertion in the 5'-untranslated region (96642) were selected for phenotyping nodulation. Plants of all three mutant lines showed a decrease in long infection threads and nodules, and an increase in incipient infection threads. About 4h after inoculation, the roots of mutant plants exhibited a greater transient accumulation of nitric oxide (NO) than did the wild-type roots; nevertheless, in vitro NO dioxygenase activities of the wild-type, A102V, and E127K proteins were similar, suggesting that the mutated proteins are not fully functional in vivo. The expression of LjGlb1-1, but not of the other class 1 Hb of L. japonicus (LjGlb1-2), was affected during infection of wild-type roots, further supporting a specific role for LjGlb1-1. In conclusion, the LjGlb1-1 mutants reveal that this protein is required during rhizobial infection and regulates NO levels.

AB - Leghemoglobins transport and deliver O 2 to the symbiosomes inside legume nodules and are essential for nitrogen fixation. However, the roles of other hemoglobins (Hbs) in the rhizobia-legume symbiosis are unclear. Several Lotus japonicus mutants affecting LjGlb1-1, a non-symbiotic class 1 Hb, have been used to study the function of this protein in symbiosis. Two TILLING alleles with single amino acid substitutions (A102V and E127K) and a LORE1 null allele with a retrotransposon insertion in the 5'-untranslated region (96642) were selected for phenotyping nodulation. Plants of all three mutant lines showed a decrease in long infection threads and nodules, and an increase in incipient infection threads. About 4h after inoculation, the roots of mutant plants exhibited a greater transient accumulation of nitric oxide (NO) than did the wild-type roots; nevertheless, in vitro NO dioxygenase activities of the wild-type, A102V, and E127K proteins were similar, suggesting that the mutated proteins are not fully functional in vivo. The expression of LjGlb1-1, but not of the other class 1 Hb of L. japonicus (LjGlb1-2), was affected during infection of wild-type roots, further supporting a specific role for LjGlb1-1. In conclusion, the LjGlb1-1 mutants reveal that this protein is required during rhizobial infection and regulates NO levels.

KW - Hemoglobin

KW - Lotus japonicus

KW - Mesorhizobium loti

KW - nitric oxide

KW - nitrogen fixation

KW - nodulation mutants

KW - symbiosis

UR - http://www.scopus.com/inward/record.url?scp=84988358526&partnerID=8YFLogxK

U2 - 10.1093/jxb/erw290

DO - 10.1093/jxb/erw290

M3 - Journal article

C2 - 27443280

SN - 0022-0957

VL - 67

SP - 5275

EP - 5283

JO - Journal of Experimental Botany

JF - Journal of Experimental Botany

IS - 17

ER -