Effects of endogenous salicylic acid on nodulation in the model legumes Lotus japonicus and Medicago truncatula.
The exogenous addition of salicylic acid (SA) was previously shown to inhibit indeterminate but not determinate-type nodulation. We sought to extend these results by modulating endogenous levels of SA through the transgenic expression of salicylate hydroxylase (NahG) in both stably transformed Lotus japonicus and composite Medicago truncatula plants. NahG expression in L. japonicus resulted in a marked reduction of SA levels. This reduction correlated with an increase in the number of infections and mean nodule number when compared to controls. However, a complicating factor was that NahG-expressing plants had greater root growth. Spot inoculations of NahG-expressing L. japonicus plants confirmed increased nodulation in these plants. Consistent with the reported inhibitory effects of exogenous SA on indeterminate-type nodulation, NahG expression in M. truncatula plants led to enhanced nodulation and infection. These data point to an important role for SA-mediated plant defense pathways in controlling nodule formation on both determinate and indeterminate nodule-forming hosts.
Stacey
Gary
G
Department of Microbiology, University of Tennessee, Knoxville, Tennessee 37996, USA. staceyg@missouri.edu
McAlvin
Crystal Bickley
CB
Kim
Sung-Yong
SY
Olivares
José
J
Soto
María José
MJ
D020561:Alphaproteobacteria / Q000502:physiology; D000070116:Lotus / Q000235:genetics / Q000378:metabolism* / Q000382:microbiology; D046913:Medicago truncatula / Q000235:genetics / Q000378:metabolism* / Q000382:microbiology; D006899:Mixed Function Oxygenases / Q000235:genetics / Q000378:metabolism; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D018517:Plant Roots / Q000254:growth & development / Q000378:metabolism / Q000382:microbiology; D030821:Plants, Genetically Modified / Q000254:growth & development / Q000378:metabolism / Q000382:microbiology; D012230:Rhizobiaceae / Q000502:physiology; D020156:Salicylic Acid / Q000378:metabolism*
D010940:Plant Proteins; D006899:Mixed Function Oxygenases; C022619:salicylate 1-monooxygenase; D020156:Salicylic Acid