Open AccessMesorhizobium loti Increases Root-Specific Expression of a Calcium-Binding Protein Homologue Identified by Promoter Tagging in Lotus japonicus
Author(s) -
K. Judith Webb,
Leif Skøt,
M. N. Nicholson,
Bodil Jørgensen,
S. Mizen
Publication year - 2000
Publication title -
molecular plant-microbe interactions
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.565
H-Index - 153
eISSN - 1943-7706
pISSN - 0894-0282
DOI - 10.1094/mpmi.2000.13.6.606
Subject(s) - lotus japonicus , biology , gene , mutant , rhizobia , root hair , reporter gene , gene expression , lotus , root nodule , microbiology and biotechnology , mesorhizobium , botany , genetics , symbiosis , bacteria
A promoter tagging program in the legume Lotus japonicus was initiated to identify plant genes involved in the nitrogen-fixing symbiosis between legumes and rhizobia. Seven transformed plant lines expressing the promoterless reporter gene uidA (β-glucuronidase; GUS) specifically in roots and/or nodules were identified. Four of these expressed GUS in the roots only after inoculation with nodule-forming Mesorhizobium loti. In one line (T90), GUS activity was found in the root epidermis, including root hairs. During seedling growth, GUS expression gradually became focused in developing nodules and disappeared from root tissue. No GUS activity was detected when a non-nodulating mutant of M. loti was used to inoculate the plants. The T-DNA insertion in this plant line was located 1.3 kb upstream of a putative coding sequence with strong homology to calcium-binding proteins. Four motifs were identified, which were very similar to the “EF hands” in calmodulin-related proteins, each binding one Ca 2+ . We have named the gene LjCbp1 (calcium-binding protein). Northern (RNA) analyses showed that this gene is expressed specifically in roots of L. japonicus. Expression was reduced in roots inoculated with non-nodulating M. loti mutants and in progeny homozygous for the T-DNA insertion, suggesting a link between the T-DNA insertion and this gene.