Strigolactone biosynthesis in Medicago truncatula and rice requires the symbiotic GRAS-type transcription factors NSP1 and NSP2.
Legume GRAS (GAI, RGA, SCR)-type transcription factors NODULATION SIGNALING PATHWAY1 (NSP1) and NSP2 are essential for rhizobium Nod factor-induced nodulation. Both proteins are considered to be Nod factor response factors regulating gene expression after symbiotic signaling. However, legume NSP1 and NSP2 can be functionally replaced by nonlegume orthologs, including rice (Oryza sativa) NSP1 and NSP2, indicating that both proteins are functionally conserved in higher plants. Here, we show that NSP1 and NSP2 are indispensable for strigolactone (SL) biosynthesis in the legume Medicago truncatula and in rice. Mutant nsp1 plants do not produce SLs, whereas in M. truncatula, NSP2 is essential for conversion of orobanchol into didehydro-orobanchol, which is the main SL produced by this species. The disturbed SL biosynthesis in nsp1 nsp2 mutant backgrounds correlates with reduced expression of DWARF27, a gene essential for SL biosynthesis. Rice and M. truncatula represent distinct phylogenetic lineages that split approximately 150 million years ago. Therefore, we conclude that regulation of SL biosynthesis by NSP1 and NSP2 is an ancestral function conserved in higher plants. NSP1 and NSP2 are single-copy genes in legumes, which implies that both proteins fulfill dual regulatory functions to control downstream targets after rhizobium-induced signaling as well as SL biosynthesis in nonsymbiotic conditions.
Department of Plant Science, Laboratory of Molecular Biology, Wageningen University, 6708 PB Wageningen, The Netherlands.
Wei
W
Liu
Wouter
W
Kohlen
Alessandra
A
Lillo
Rik
R
Op den Camp
Sergey
S
Ivanov
Marijke
M
Hartog
Erik
E
Limpens
Muhammad
M
Jamil
Cezary
C
Smaczniak
Kerstin
K
Kaufmann
Wei-Cai
WC
Yang
Guido J E J
GJ
Hooiveld
Tatsiana
T
Charnikhova
Harro J
HJ
Bouwmeester
Ton
T
Bisseling
René
R
Geurts
D000595:Amino Acid Sequence; D002338:Carotenoids / Q000032:analysis / Q000378:metabolism; D015536:Down-Regulation; D020869:Gene Expression Profiling; D018506:Gene Expression Regulation, Plant; D007783:Lactones / Q000032:analysis / Q000737:chemistry / Q000378:metabolism*; D046913:Medicago truncatula / Q000235:genetics / Q000254:growth & development / Q000382:microbiology / Q000502:physiology*; D008969:Molecular Sequence Data; D009154:Mutation; D020411:Oligonucleotide Array Sequence Analysis; D012275:Oryza / Q000235:genetics / Q000254:growth & development / Q000382:microbiology / Q000502:physiology*; D010641:Phenotype; D010802:Phylogeny; D010937:Plant Growth Regulators / Q000378:metabolism; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D055170:Plant Root Nodulation; D018517:Plant Roots / Q000235:genetics / Q000254:growth & development / Q000382:microbiology / Q000502:physiology; D012717:Sesquiterpenes / Q000378:metabolism; D015398:Signal Transduction; D016962:Sinorhizobium meliloti / Q000502:physiology*; D013559:Symbiosis; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*
D007783:Lactones; D010937:Plant Growth Regulators; D010940:Plant Proteins; D012717:Sesquiterpenes; D014157:Transcription Factors; D002338:Carotenoids