The molecular mechanisms underlying mycorrhizal symbioses, the most ubiquitous and impactful mutualistic plant-microbial interaction in nature, are largely unknown. Through genetic mapping, re-sequencing and molecular validation, we demonstrate that a G-type lectin receptor-like kinase mediates the symbiotic interaction between Populus and ectomycorrhizal fungus Laccaria bicolor. This finding uncovers an important molecular step in the establishment of symbiotic plant-fungal associations and provides a molecular target for engineering beneficial mycorrhizal relationships.
Three-Amino-acid-Loop-Extension(TALE) homeodomain transcription factor BLH3 regulates timing of transition from vegetative to reproductive phase. Previous preliminary results obtained using large-scale yeast two-hybrids indicate that BLH3 protein possibly interact with Ovate Family Proteins(OFPs) transcription co-regulators. Nevertheless, it is uncertain whether OFP1-BLH3 complex is involved in regulation of timing of transition from vegetative to reproductive phase in Arabidopsis. The interaction between BLH3 and OFP1 was re-tested and verified by a yeast two-hybrid system. We found that the BLH3-OFP1 interaction was mainly mediated through the BLH3 homeodomain. Meanwhile, this interaction was further confirmed by bimolecular fluorescence complementation (BiFC) in vivo. Further, by establishing protoplast transient expression, we discovered that BLH3 acts as a transcriptional activator, whereas OFP1 functioned as a repressor. The interactions between OFP1 and BLH3 can reduce BLH3 transcriptional activity. The ofp1 mutant lines and blh3 mutant lines, OFP1 overexpress lines and BLH3 overexpress lines can both influence timing of transition from vegetative to reproductive phase. Furthermore, 35s:OFP1/blh3 plants exhibited flowering and leaf quantity similar to that of the wild-type controls. 35s:BLH3/ofp1 plants flowered earlier and had less leaves than wild-type controls, indicating that OFP1 protein might depend partially on BLH3 in its function to regulate the timing of transition from vegetative to reproductive phase. These results support our assumption that, by interacting with OFP1, BLH3 forms a functional protein complex that controls timing of progression from vegetative to reproductive phase, and OFP1 might negatively regulate BLH3 or the BLH-KNOX complex, an important interaction for sustaining the normal transition from vegetative to reproductive phase.
Phenylalanine ammonia-lyase (PAL) and cinnamate 4-hydroxylase (C4H) are the first and second key enzymes of the phenylpropanoid pathway. Systematic analysis of the DfPAL gene family and DfC4H have not been performed in Dryopteris fragrans (L.) Schott. To date, PAL and C4H genes have been less extensively studied in monilophytes than in angiosperms. Here we report the identification of threeDfPAL and DfC4H fragments using cDNA cloning and sequencing. Bioinformatics and phylogenetic analyses showed that DfPAL1 and DfPAL2 were quite similar at the amino acid level (94.88%), whereas DfPAL3 was relatively low similar to both of the other paralogs. Some important functional domains were conserved in three DfPAL and DfC4H genes. DfPAL3 and DfC4H were highly expressed in gametophytes and petioles of D. fragrans, DfPAL1 had the highest expression in petioles, and DfPAL2 had low expression in leaves and petioles. Only DfPAL2 and DfC4H were induced with 4°C, 35°C, and UV treatments, but the time responses were different. These results suggest complexity of the DfPAL- and DfC4H-associated metabolic network in D. fragrans. The results provide a basis for elucidating the role of DfPAL and DfC4H genes in the biosynthesis of bioactive compounds.
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