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Plant Physiol ; 159(4): 1671-85, 2012 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-22652128

RESUMO

The formation of root nodules and arbuscular mycorrhizal (AM) roots is controlled by a common signaling pathway including the calcium/calmodulin-dependent kinase Doesn't Make Infection3 (DMI3). While nodule initiation by lipochitooligosaccharide (LCO) Nod factors is well characterized, diffusible AM fungal signals were only recently identified as sulfated and nonsulfated LCOs. Irrespective of different outcomes, the perception of symbiotic LCOs in Medicago truncatula is mediated by the LysM receptor kinase M. truncatula Nod factor perception (MtNFP). To shed light on transcriptional responses toward symbiotic LCOs and their dependence on MtNFP and Ca(2+) signaling, we performed genome-wide expression studies of wild-type, Nod-factor-perception mutant1, and dmi3 mutant roots challenged with Myc- and Nod-LCOs. We show that Myc-LCOs lead to transient, quick responses in the wild type, whereas Nod-LCOs require prolonged incubation for maximal expression activation. While Nod-LCOs are most efficient for an induction of persistent transcriptional changes, sulfated Myc-LCOs are less active, and nonsulfated Myc-LCOs display the lowest capacity to activate and sustain expression. Although all symbiotic LCOs up-regulated a common set of genes, discrete subsets were induced by individual LCOs, suggesting common and specific functions for these in presymbiotic signaling. Surprisingly, even sulfated fungal Myc-LCOs and Sinorhizobium meliloti Nod-LCOs, having very similar structures, each elicited discrete subsets of genes, while a mixture of both Myc-LCOs activated responses deviating from those induced by single treatments. Focusing on the precontact phase, we identified signaling-related and transcription factor genes specifically up-regulated by Myc-LCOs. Comparative gene expression studies in symbiotic mutants demonstrated that transcriptional reprogramming by AM fungal LCOs strictly depends on MtNFP and largely requires MtDMI3.


Assuntos
Regulação da Expressão Gênica de Plantas/efeitos dos fármacos , Lipopolissacarídeos/farmacologia , Medicago truncatula/genética , Micorrizas/fisiologia , Proteínas de Plantas/metabolismo , Simbiose/efeitos dos fármacos , Transcrição Gênica/efeitos dos fármacos , Bioensaio , Difusão/efeitos dos fármacos , Genes de Plantas/genética , Interações Hospedeiro-Patógeno/efeitos dos fármacos , Interações Hospedeiro-Patógeno/genética , Cinética , Medicago truncatula/efeitos dos fármacos , Medicago truncatula/microbiologia , Modelos Biológicos , Mutação/genética , Micorrizas/efeitos dos fármacos , Proteínas de Plantas/genética , Raízes de Plantas/efeitos dos fármacos , Raízes de Plantas/genética , Raízes de Plantas/microbiologia , Regiões Promotoras Genéticas/genética , Reprodutibilidade dos Testes , Transdução de Sinais/efeitos dos fármacos , Transdução de Sinais/genética , Simbiose/genética , Fatores de Transcrição/genética , Fatores de Transcrição/metabolismo , Ativação Transcricional/efeitos dos fármacos , Ativação Transcricional/genética
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