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Proteins with a domain of unknown function (DUF) represent a number of gene families that encode functionally uncharacterized proteins in eukaryotes. In particular, members of the DUF1005 family in plants have a 411-amino-acid conserved domain, and this family has not been described previously. In this study, a total of 302 high-confidence DUF1005 family members were identified from 58 plant species, and none were found in the four algae that were selected. Thus, this result showed that DUF1005s might belong to a kind of plant-specific gene family, and this family has not been evolutionarily expanded. Phylogenetic analysis showed that the DUF1005 family genes could be classified into four subgroups in 58 plant species. The earliest group to emerge was Group I, including a total of 100 gene sequences, and this group was present in almost all selected species spanning from mosses to seed plants. Group II and Group III, with 69 and 74 members, respectively, belong to angiosperms. Finally, with 59 members, Group IV was the last batch of genes to emerge, and this group is unique to dicotyledons. Expression pattern analysis of the CiDUF1005, a member of the DUF1005 family from Caragana intermedia, showed that CiDUF1005 genes were differentially regulated under various treatments. Compared to the wild type, transgenic lines with heterologous CiDUF1005 expression in Arabidopsis thaliana had longer primary roots and more lateral roots. These results expanded our knowledge of the evolution of the DUF1005 family in plants and will contribute to elucidating biological functions of the DUF1005 family in the future.

Background Domain of unknown function (DUF) proteins represent a number of gene families that encode functionally uncharacterized proteins in eukaryotes. The DUF4228 gene family is one of these families in plants that has not been described previously. Results In this study, we performed an extensive comparative analysis of DUF4228 proteins and determined their phylogeny in the plant lineage. A total of 489 high-confidence DUF4228 family members were identified from 14 land plant species, which sub-divided into three distinct phylogenetic groups: group I, group II and group III. A highly conserved DUF4228 domain and motif distribution existed in each group, implying their functional conservation. To reveal the possible biological functions of these DUF4228 genes, 25 ATDUF4228 sequences from Arabidopsis thaliana were selected for further analysis of characteristics such as their chromosomal position, gene duplications and gene structures. Ka/Ks analysis identified seven segmental duplication events, while no tandemly duplication gene pairs were found in A. thaliana. Some cis-elements responding to abiotic stress and phytohormones were identified in the upstream sequences of the ATDUF4228 genes. Expression profiling of the ATDUF4228 genes under abiotic stresses (mainly osmotic, salt and cold) and protein-protein interaction prediction suggested that some ATDUF4228 genes are may be involved in the pathways of plant resistance to abiotic stresses. Conclusion These results expand our knowledge of the evolution of the DUF4228 gene family in plants and will contribute to the elucidation of the biological functions of DUF4228 genes in the future.

Type 2 C protein phosphatases (PP2Cs) represent the major group of protein phosphatases in plants and play important roles in various plant processes. In this study, 94 MtPP2C genes were identified from Medicago truncatula and further phylogenetically classified into 13 subfamilies, as supported by exon-intron organization and conserved motif composition. Collinearity analysis indicated that segmental duplication events played a crucial role in the expansion of MtPP2C gene families in M. truncatula. Furthermore, the expression profiles of MtPP2Cs under different abiotic treatments were analyzed using qRT-PCR. Results showed that these MtPP2Cs genes displayed different expression patterns in response to drought, cold and ABA stress conditions and some of the key stress responsive MtPP2Cs genes have been identified. Our study presents a comprehensive overview of the PP2C gene family in M. truncatula, which will be useful for further functional characterization of MtPP2Cs in plant drought and cold stress responses.

Additional file 3: Figure S1. Details of the phylogenetic classification of DUF4228 genes in land plant lineages. Phylogenetic tree was constructed using the ML method with IQ-tree. Green lines represent bryophytes, pink lines represent pteridophytes, blue lines represent gymnosperms and red lines represent angiosperms.