ABSTRACT
Oxalate oxidases (OxO) catalyse the degradation of oxalic acid (OA). Highly resistant transgenic soybean carrying an OxO gene and its susceptible parent soybean line, AC Colibri, were tested for genome-wide gene expression in response to the necrotrophic, OA-producing pathogen Sclerotinia sclerotiorum using soybean cDNA microarrays. The genes with changed expression at statistically significant levels (overall F-test P-value cut-off of 0.0001) were classified into functional categories and pathways, and were analysed to evaluate the differences in transcriptome profiles. Although many genes and pathways were found to be similarly activated or repressed in both genotypes after inoculation with S. sclerotiorum, the OxO genotype displayed a measurably faster induction of basal defence responses, as observed by the differential changes in defence-related and secondary metabolite genes compared with its susceptible parent AC Colibri. In addition, the experiment presented provides data on several other transcripts that support the hypothesis that S. sclerotiorum at least partially elicits the hypersensitive response, induces lignin synthesis (cinnamoyl CoA reductase) and elicits as yet unstudied signalling pathways (G-protein-coupled receptor and related). Of the nine genes showing the most extreme opposite directions of expression between genotypes, eight were related to photosynthesis and/or oxidation, highlighting the importance of redox in the control of this pathogen.
Subject(s)
Ascomycota/pathogenicity , Glycine max/genetics , Glycine max/microbiology , Plant Diseases/genetics , Plant Diseases/microbiology , Base Sequence , DNA, Plant/genetics , Disease Resistance/genetics , GTP-Binding Proteins/genetics , GTP-Binding Proteins/metabolism , Gene Expression Regulation, Plant , Genome, Plant , Lignin/genetics , Lignin/metabolism , Molecular Sequence Data , Oxalates , Oxidoreductases/genetics , Oxidoreductases/metabolism , Peroxidases/genetics , Peroxidases/metabolism , Plant Proteins/genetics , Plant Proteins/metabolism , Plants, Genetically Modified , Glycine max/metabolism , TranscriptomeABSTRACT
The soybean (Glycine max) genome contains 18 members of the 14-3-3 protein family, but little is known about their association with specific phenotypes. Here, we report that the Glyma0529080 Soybean G-box Factor 14-3-3c (SGF14c) and Glyma08g12220 (SGF14l) genes, encoding 14-3-3 proteins, appear to play essential roles in soybean nodulation. Quantitative reverse transcription-polymerase chain reaction and western-immunoblot analyses showed that SGF14c mRNA and protein levels were specifically increased in abundance in nodulated soybean roots 10, 12, 16, and 20 d after inoculation with Bradyrhizobium japonicum. To investigate the role of SGF14c during soybean nodulation, RNA interference was employed to silence SGF14c expression in soybean roots using Agrobacterium rhizogenes-mediated root transformation. Due to the paleopolyploid nature of soybean, designing a specific RNA interference sequence that exclusively targeted SGF14c was not possible. Therefore, two highly similar paralogs (SGF14c and SGF14l) that have been shown to function as dimers were silenced. Transcriptomic and proteomic analyses showed that mRNA and protein levels were significantly reduced in the SGF14c/SGF14l-silenced roots, and these roots exhibited reduced numbers of mature nodules. In addition, SGF14c/SGF14l-silenced roots contained large numbers of arrested nodule primordia following B. japonicum inoculation. Transmission electron microscopy further revealed that the host cytoplasm and membranes, except the symbiosome membrane, were severely degraded in the failed nodules. Altogether, transcriptomic, proteomic, and cytological data suggest a critical role of one or both of these 14-3-3 proteins in early development stages of soybean nodules.
Subject(s)
14-3-3 Proteins/metabolism , Glycine max/physiology , Plant Proteins/metabolism , Plant Root Nodulation/physiology , 14-3-3 Proteins/genetics , Bradyrhizobium/physiology , Gene Expression Regulation, Plant , Gene Silencing , Genes, Plant/genetics , Immunoblotting , Mass Spectrometry , Multigene Family , Phylogeny , Plant Proteins/genetics , Plant Root Nodulation/genetics , Plants, Genetically Modified , Proteomics , RNA, Messenger/genetics , RNA, Messenger/metabolism , Root Nodules, Plant/cytology , Root Nodules, Plant/genetics , Root Nodules, Plant/microbiology , Root Nodules, Plant/ultrastructure , Glycine max/genetics , Glycine max/microbiology , Glycine max/ultrastructure , Symbiosis/genetics , Transcriptome/geneticsABSTRACT
Nodulation is the result of a mutualistic interaction between legumes and symbiotic soil bacteria (e.g. soybean [Glycine max] and Bradyrhizobium japonicum) initiated by the infection of plant root hair cells by the symbiont. Fewer than 20 plant genes involved in the nodulation process have been functionally characterized. Considering the complexity of the symbiosis, significantly more genes are likely involved. To identify genes involved in root hair cell infection, we performed a large-scale transcriptome analysis of B. japonicum-inoculated and mock-inoculated soybean root hairs using three different technologies: microarray hybridization, Illumina sequencing, and quantitative real-time reverse transcription-polymerase chain reaction. Together, a total of 1,973 soybean genes were differentially expressed with high significance during root hair infection, including orthologs of previously characterized root hair infection-related genes such as NFR5 and NIN. The regulation of 60 genes was confirmed by quantitative real-time reverse transcription-polymerase chain reaction. Our analysis also highlighted changes in the expression pattern of some homeologous and tandemly duplicated soybean genes, supporting their rapid specialization.
