The evolutionary history of the E2F and DEL genes in Viridiplantae.

The E2 promoter binding factor (E2F) proteins are present in almost all eukaryotic organisms and are essential to control several processes, such as the cell cycle progression, cell division, DNA replication, and apoptosis. The E2F family comprises two different types of proteins: the typical E2Fs and atypical E2Fs, which differ structurally and have specific functions. The E2F gene family was described for the first time in plants in 1999, and since then several studies have focused on the functional aspects, but the evolutionary history of this gene family is still unknown. Here, we investigated the evolutionary history of the E2F gene family in plants. Our findings suggest that E2F proteins arose early after the emergence of the eukaryotic species, while DEL proteins appear to have arisen before the metazoan and plants origin probably through a partial duplication of an ancient E2F protein. Our data also suggest that E2Fs activators and repressors appeared twice during evolution, once in the metazoan lineage and again in the embryophyte lineage.

Caspases in plants: metacaspase gene family in plant stress responses.

Programmed cell death (PCD) is an ordered cell suicide that removes unwanted or damaged cells, playing a role in defense to environmental stresses and pathogen invasion. PCD is component of the life cycle of plants, occurring throughout development from embryogenesis to the death. Metacaspases are cysteine proteases present in plants, fungi, and protists. In certain plant-pathogen interactions, the PCD seems to be mediated by metacaspases. We adopted a comparative genomic approach to identify genes coding for the metacaspases in Viridiplantae. We observed that the metacaspase was divided into types I and II, based on their protein structure. The type I has a metacaspase domain at the C-terminus region, presenting or not a zinc finger motif in the N-terminus region and a prodomain rich in proline. Metacaspase type II does not feature the prodomain and the zinc finger, but has a linker between caspase-like catalytic domains of 20 kDa (p20) and 10 kDa (p10). A high conservation was observed in the zinc finger domain (type I proteins) and in p20 and p10 subunits (types I and II proteins). The phylogeny showed that the metacaspases are divided into three principal groups: type I with and without zinc finger domain and type II metacaspases. The algae and moss are presented as outgroup, suggesting that these three classes of metacaspases originated in the early stages of Viridiplantae, being the absence of the zinc finger domain the ancient condition. The study of metacaspase can clarify their assignment and involvement in plant PCD mechanisms.

The phylogeny and evolutionary history of the Lesion Simulating Disease (LSD) gene family in Viridiplantae.

The Lesion Simulating Disease (LSD) genes encode a family of zinc finger proteins that play a role in programmed cell death (PCD) and other biological processes, such as plant growth and photosynthesis. In the present study, we report the reconstruction of the evolutionary history of the LSD gene family in Viridiplantae. Phylogenetic analysis revealed that the monocot and eudicot genes were distributed along the phylogeny, indicating that the expansion of the family occurred prior to the diversification between these clades. Sequences encoding proteins that present one, two, or three LSD domains formed separate groups. The secondary structure of these different LSD proteins presented a similar composition, with the ß-sheets being their main component. The evolution by gene duplication was identified only to the genes that contain three LSD domains, which generated proteins with equal structure. Moreover, genes encoding proteins with one or two LSD domains evolved as single-copy genes and did not result from loss or gain in LSD domains. These results were corroborated by synteny analysis among regions containing paralogous/orthologous genes in Glycine max and Populus trichocarpa. The Ka/Ks ratio between paralogous/orthologous genes revealed that a subfunctionalization process possibly could be occurring with the LSD genes, explaining the involvement of LSD members in different biological processes, in addition to the negative regulation of PCD. This study presents important novelty in the evolutionary history of the LSD family and provides a basis for future research on individual LSD genes and their involvement in important pathway networks in plants.

Genome-wide annotation of the soybean WRKY family and functional characterization of genes involved in response to Phakopsora pachyrhizi infection.

BACKGROUND: Many previous studies have shown that soybean WRKY transcription factors are involved in the plant response to biotic and abiotic stresses. Phakopsora pachyrhizi is the causal agent of Asian Soybean Rust, one of the most important soybean diseases. There are evidences that WRKYs are involved in the resistance of some soybean genotypes against that fungus. The number of WRKY genes already annotated in soybean genome was underrepresented. In the present study, a genome-wide annotation of the soybean WRKY family was carried out and members involved in the response to P. pachyrhizi were identified. RESULTS: As a result of a soybean genomic databases search, 182 WRKY-encoding genes were annotated and 33 putative pseudogenes identified. Genes involved in the response to P. pachyrhizi infection were identified using superSAGE, RNA-Seq of microdissected lesions and microarray experiments. Seventy-five genes were differentially expressed during fungal infection. The expression of eight WRKY genes was validated by RT-qPCR. The expression of these genes in a resistant genotype was earlier and/or stronger compared with a susceptible genotype in response to P. pachyrhizi infection. Soybean somatic embryos were transformed in order to overexpress or silence WRKY genes. Embryos overexpressing a WRKY gene were obtained, but they were unable to convert into plants. When infected with P. pachyrhizi, the leaves of the silenced transgenic line showed a higher number of lesions than the wild-type plants. CONCLUSIONS: The present study reports a genome-wide annotation of soybean WRKY family. The participation of some members in response to P. pachyrhizi infection was demonstrated. The results contribute to the elucidation of gene function and suggest the manipulation of WRKYs as a strategy to increase fungal resistance in soybean plants.

The Lesion Simulating Disease (LSD) gene family as a variable in soybean response to Phakopsora pachyrhizi infection and dehydration.

The Lesion Simulating Disease (LSD) genes encode a family of zinc finger proteins that are reported to play an important role in the hypersensitive response and programmed cell death (PCD) that are caused by biotic and abiotic stresses. In the present study, 117 putative LSD family members were identified in Viridiplantae. Genes with one, two, or three conserved LSD domains were identified. Proteins with three LSD domains were highly represented in the species analyzed and were present in basal organisms. Proteins with two LSD domains were identified only in the Embryophyte clade, and proteins possessing one LSD domain were highly represented in grass species. Expression analyses of Glycine max LSD (GmLSD) genes were performed by real-time quantitative polymerase chain reaction. The results indicated that GmLSD genes are not ubiquitously expressed in soybean organs and that their expression patterns are instead organ-dependent. The expression of the majority of GmLSD genes is modulated in soybean during Phakopsora pachyrhizi infection. In addition, the expression of some GmLSD genes is modulated in plants under dehydration stress. These results suggest the involvement of GmLSD genes in the response of soybean to both biotic and abiotic stresses.

Identification of the soybean HyPRP family and specific gene response to Asian soybean rust disease.

Soybean [Glycine max (L.) Merril], one of the most important crop species in the world, is very susceptible to abiotic and biotic stress. Soybean plants have developed a variety of molecular mechanisms that help them survive stressful conditions. Hybrid proline-rich proteins (HyPRPs) constitute a family of cell-wall proteins with a variable N-terminal domain and conserved C-terminal domain that is phylogenetically related to non-specific lipid transfer proteins. Members of the HyPRP family are involved in basic cellular processes and their expression and activity are modulated by environmental factors. In this study, microarray analysis and real time RT-qPCR were used to identify putative HyPRP genes in the soybean genome and to assess their expression in different plant tissues. Some of the genes were also analyzed by time-course real time RT-qPCR in response to infection by Phakopsora pachyrhizi, the causal agent of Asian soybean rust disease. Our findings indicate that the time of induction of a defense pathway is crucial in triggering the soybean resistance response to P. pachyrhizi. This is the first study to identify the soybean HyPRP group B family and to analyze disease-responsive GmHyPRP during infection by P. pachyrhizi.