RESUMO
We report here the molecular and phenotypic features of a library of 31,562 insertion lines generated in the model japonica cultivar Nipponbare of rice (Oryza sativa L.), called Oryza Tag Line (OTL). Sixteen thousand eight hundred and fourteen T-DNA and 12,410 Tos17 discrete insertion sites have been characterized in these lines. We estimate that 8686 predicted gene intervals--i.e. one-fourth to one-fifth of the estimated rice nontransposable element gene complement--are interrupted by sequence-indexed T-DNA (6563 genes) and/or Tos17 (2755 genes) inserts. Six hundred and forty-three genes are interrupted by both T-DNA and Tos17 inserts. High quality of the sequence indexation of the T2 seed samples was ascertained by several approaches. Field evaluation under agronomic conditions of 27,832 OTL has revealed that 18.2% exhibit at least one morphophysiological alteration in the T1 progeny plants. Screening 10,000 lines for altered response to inoculation by the fungal pathogen Magnaporthe oryzae allowed to observe 71 lines (0.7%) developing spontaneous lesions simulating disease mutants and 43 lines (0.4%) exhibiting an enhanced disease resistance or susceptibility. We show here that at least 3.5% (four of 114) of these alterations are tagged by the mutagens. The presence of allelic series of sequence-indexed mutations in a gene among OTL that exhibit a convergent phenotype clearly increases the chance of establishing a linkage between alterations and inserts. This convergence approach is illustrated by the identification of the rice ortholog of AtPHO2, the disruption of which causes a lesion-mimic phenotype owing to an over-accumulation of phosphate, in nine lines bearing allelic insertions.
Assuntos
DNA Bacteriano , Biblioteca Gênica , Mutagênese Insercional , Oryza/genética , DNA de Plantas/genética , Genes de Plantas , Magnaporthe/patogenicidade , Fenótipo , Doenças das Plantas/genética , Plasmídeos , Análise de Sequência de DNA , Transformação GenéticaRESUMO
* Blast disease (causal agent Magnaporthe oryzae) has presented as a new and serious field disease of wheat in South America. Here, we investigated the responses of wheat to both adapted and nonadapted isolates of the blast fungus Magnaporthe, examining cellular defence and transcriptional changes. * Resistance towards the nonadapted isolate was associated with the formation of appositions, here termed halos, beneath attempted Magnaporthe grisea penetration sites that wheat-adapted, M. oryzae isolates were able to breach. * Transcriptome analysis indicated extensive transcriptional reprogramming following inoculation with both wheat-adapted and nonadapted isolates of Magnaporthe. Functional annotation of many of the differentially expressed transcripts classified into the categories: cell rescue and defence, plant metabolism, cellular transport and regulation of transcription (although a significant number of transcripts remain unclassified). * Defence-related transcripts induced in common by adapted and nonadapted isolates were differentially regulated in response to M. oryzae and M. grisea isolates over time. Differential expression of genes involved in cellular transport indicated the importance of this process in plant defence. Functional characterisation of these transcripts and their role in defence may eventually lead to the identification of broad-spectrum resistance mechanisms in wheat towards Magnaporthe.