Induction of thioredoxin is required for nodule development to reduce reactive oxygen species levels in soybean roots.
Nodules are formed on legume roots as a result of signaling between symbiotic partners and in response to the activities of numerous genes. We cloned fragments of differentially expressed genes in spot-inoculated soybean (Glycine max) roots. Many of the induced clones were similar to known genes related to oxidative stress, such as thioredoxin and beta-carotene hydroxylase. The deduced amino acid sequences of full-length soybean cDNAs for thioredoxin and beta-carotene hydroxylase were similar to those in other species. In situ RNA hybridization revealed that the thioredoxin gene is expressed on the pericycle of 2-d-old nodules and in the infected cells of mature nodules, suggesting that thioredoxin is involved in nodule development. The thioredoxin promoter was found to contain a sequence resembling an antioxidant responsive element. When a thioredoxin mutant of yeast was transformed with the soybean thioredoxin gene it became hydrogen peroxide tolerant. These observations prompted us to measure reactive oxygen species levels. These were decreased by 3- to 5-fold in 7-d-old and 27-d-old nodules, coincident with increases in the expression of thioredoxin and beta-carotene hydroxylase genes. Hydrogen peroxide-producing regions identified with cerium chloride were found in uninoculated roots and 2-d-old nodules, but not in 7-d-old and 27-d-old nodules. RNA interference-mediated repression of the thioredoxin gene severely impaired nodule development. These data indicate that antioxidants such as thioredoxin are essential to lower reactive oxygen species levels during nodule development.
Lee
Mi-Young
MY
Department of Biological Science, Sookmyung Women's University, Seoul 140-742, Korea.
Shin
Ki-Hye
KH
Kim
Yun-Kyoung
YK
Suh
Ji-Yeon
JY
Gu
Young-Yun
YY
Kim
Mi-Ran
MR
Hur
Yoon-Sun
YS
Son
Ora
O
Kim
Jin-Sun
JS
Song
Eunsook
E
Lee
Myeong-Sok
MS
Nam
Kyoung Hee
KH
Hwang
Keum Hee
KH
Sung
Mi-Kyung
MK
Kim
Ho-Jung
HJ
Chun
Jong-Yoon
JY
Park
Miey
M
Ahn
Tae-In
TI
Hong
Choo Bong
CB
Lee
Suk-Ha
SH
Park
Hong Jae
HJ
Park
Jong-Sug
JS
Verma
Desh Pal S
DP
Cheon
Choong-Ill
CI
D000595:Amino Acid Sequence; D001483:Base Sequence; D018076:DNA, Complementary / Q000235:genetics / Q000302:isolation & purification; D018744:DNA, Plant / Q000235:genetics / Q000302:isolation & purification; D017343:Genes, Plant; D006861:Hydrogen Peroxide / Q000494:pharmacology; D006899:Mixed Function Oxygenases / Q000235:genetics; D008969:Molecular Sequence Data; D010940:Plant Proteins / Q000096:biosynthesis* / Q000235:genetics; D018517:Plant Roots / Q000254:growth & development / Q000378:metabolism / Q000382:microbiology; D011401:Promoter Regions, Genetic; D034622:RNA Interference; D017382:Reactive Oxygen Species / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D015398:Signal Transduction; D013025:Glycine max / Q000235:genetics / Q000254:growth & development* / Q000378:metabolism*; D013559:Symbiosis; D013879:Thioredoxins / Q000096:biosynthesis* / Q000235:genetics
D018076:DNA, Complementary; D018744:DNA, Plant; D010940:Plant Proteins; D017382:Reactive Oxygen Species; D013879:Thioredoxins; D006861:Hydrogen Peroxide; D006899:Mixed Function Oxygenases; C079232:beta-carotene hydroxylase