Isolation of a subfamily of genes for R2R3-MYB transcription factors showing up-regulated expression under nitrogen nutrient-limited conditions

Abstract

Plant R2R3-MYB transcription factors are encoded by more than 100 copies of genes. In this study, we attempted to isolate some members of the R2R3-MYB superfamily involved in regulation of nitrogen fixation in legumes. A library of 300 recombinant plasmid clones containing the R2R3-MYB fragments of the superfamily was screened by differential hybridization to isolate R2R3-MYB genes whose expression was up-regulated under nitrogen nutrient-limited conditions. Two groups of clones were identified, each of which seemed to represent a gene responsive to nitrogen starvation. The entire coding regions for the genes were further isolated by PCR and were designated LjMYB101 and LjMYB102. By screening a genomic library of Lotus japonicus with a probe derived from LjMYB101, the third gene, LjMYB103, was isolated. In addition, a candidate for the soybean orthologue of LjMYB101 was isolated and designated GmMYB101. Sequence alignment of the genes with members of the plant R2R3-MYB superfamily showed that they all belonged to the subgroup 10 of the superfamily. The expression analysis of the genes showed that the organ-specific and nitrate-regulated expression profile of MYB101 was very similar to that of CHS in Lotus as well as in soybean, suggesting a possible role for MYB101 in regulation of flavonoid biosynthesis in response to nitrate starvation. On the other hand, an interesting relationship, in structure and function, was found between LjMYB101 and LjGln1, suggesting an alternative role for MYB101 in regulation of nitrogen metabolism.

R2R3-type MYB transcription factor, CmMYB1, is a central nitrogen assimilation regulator in Cyanidioschyzon merolae

“…In Pinus sylvestris, PtMYB1 and PtMYB3, 2 R2R3-type MYB type TFs were shown to directly bind to the promoter region of the glutamine synthetase gene (19). In Lotus japonicus, 3 R2R3-type MYB TFs, LiMYB101, LiMYB102, and LiMYB103, were isolated, expressions of which were activated by nitrogen depletion in an organ specific manner (20). Lian et al analyzed the expression profiles of rice seedlings under nitrogen-depletion stress using a microarray of 11,494 rice ESTs representing 10,422 unique genes.…”

Expression of the R2R3-MYB Transcription Factor TaMYB14 fromTrifolium arvenseActivates Proanthocyanidin Biosynthesis in the LegumesTrifolium repensandMedicago sativa

“…html; GenBank accession nos. CO511688-CO517334) for sequences containing the highly conserved R2R3-MYB domain (Stracke et al, 2001;Miyake et al, 2003). We designed degenerate primers (all primer sequences used in this study are listed in Supplemental Table S1) to amplify putative R2R3-MYB TFs by RT-PCR of mRNA isolated from immature and mature T. arvense leaf tissues, cloned the PCR products, and randomly selected 200 clones for sequencing.…”

“…To predict the conserved domain of legume R2R3-MYB TFs, we used the hidden Markov model method (HMMER 3.0;Eddy, 1996) based on R2R3-MYB sequences published previously (Nesi et al, 2001;Miyake et al, 2003). EST and EST contigs from available legume sequence databases (in house: T. repens EST CS35, T. repens Pastoral Genomics NR; public: T. pratense EST contigs, Lotus japonicus EST contigs, Glycine max contigs, Medicago truncatula predicted proteins, M. sativa glandular trichome ESTs, the Dana Farber Gene Indices databases at http://compbio.dfci.harvard.edu/tgi/plant.html, http:// www.kazusa.or.jp/e/resources/index.html, and GenBank accession nos.…”

Down-regulation of the maize and Arabidopsis thaliana caffeic acid O-methyl-transferase genes by two new maize R2R3-MYB transcription factors

“…On the other hand, while ZmMYB39 is closely related to other monocot R2R3-MYB factors, whose function has not been yet attributed, ZmMYB2 is closely related to R2R3-MYB factors that have been related to nitrogen metabolism such as LjMYB101 and LjMYB103 (Miyake et al 2003).…”