| Mutant Symbol | MtMMPL1 RNAi |
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| Allele Symbol | MtMMPL1 RNAi |
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| Gene and Mutation Location | MtMMPL1 (MtN9) (RNAi covers most of the MtMMPL1 translated and 3' untranslated regions) |
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| Symbiotic Phenotype Brief | Nod+Fix+ |
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| Phenotype Detail | This RNAi construct led to an approximately 4-fold reduction in MtMMPL1 transcript levels by comparison with roots transformed with the empty vector roots (at 6 dpi with S. meliloti), as estimated by qRT-PCR analysis of pooled transformed roots. The symbiotic competence of MtMMPL1 RNAi roots was compared with that of control roots (empty vector-transformed). Similar kinetics of nodulation and nodule numbers were observed. MtMMPL1 RNAi nodules were clearly functional, since plants grew vigorously for several weeks in a medium without combined nitrogen. In fact these nodules were slightly larger (about 1.3 fold) than control nodules in 3 out of the 4 experiments performed. Decreased MtMMPL1 expression leads to an accumulation of rhizobia within infection threads, whose diameter is often significantly enlarged. Conversely, MtMMPL1 ectopic overexpression under the control of a constitutive (35S) promoter led to numerous abortive infections and an overall
decrease in the number of nodules. |
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| Single gene targeted? | yes |
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| Extra Information | Enlarged ITs due to MtMMPL1 RNAi were found in fully functional nodules with an increased Rhizobium accumulation and without any sign of plant defence responses. It could be argued that the MtMMPL1 RNAi used here corresponded to a weak mutant allele, for which an altered IT structure was perhaps the most easily observed phenotype. Bacterial
accumulation in ITs could thus result from non-optimal bacterial release, but without problems of viability since these bacteria were wild-type. Alternatively, it may be that rhizobial accumulation in MtMMPL1 RNAi nodules was due to a change in IT structure or internal composition, making it more hospitable for bacteria. |
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| Mutagenesis Method | RNAi |
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| Mutant Class | Nod+Fix+ |
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| Allelism | |
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| The earliest development stage known to be affected | N/A |
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| Wildtype Line | Jemalong A17 |
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