bims-plasge 2019-05-12 papers

Issue of 2019–05–12
five papers selected by
Vera S. Bogdanova, ИЦиГ СО РАН

BMC Genomics. 2019 May 08. 20(1): 348

Mitochondrial genome and transcriptome analysis of five alloplasmic male-sterile lines in Brassica juncea.

Zengxiang Wu, Kaining Hu, Mengjiao Yan, Liping Song, Jing Wen, Chaozhi Ma, Jinxiong Shen, Tingdong Fu, Bin Yi, Jinxing Tu.

BACKGROUND: Alloplasmic lines, in which the nuclear genome is combined with wild cytoplasm, are often characterized by cytoplasmic male sterility (CMS), regardless of whether it was derived from sexual or somatic hybridization with wild relatives. In this study, we sequenced and analyzed the mitochondrial genomes of five such alloplasmic lines in Brassica juncea.
RESULTS: The assembled and annotated mitochondrial genomes of the five alloplasmic lines were found to have virtually identical gene contents. They preserved most of the ancestral mitochondrial segments, and the same candidate male sterility gene (orf108) was found harbored in mitotype-specific sequences. We also detected promiscuous sequences of chloroplast origin that were conserved among plants of the Brassicaceae, and found the RNA editing profiles to vary across the five mitochondrial genomes.
CONCLUSIONS: On the basis of our characterization of the genetic nature of five alloplasmic mitochondrial genomes, we speculated that the putative candidate male sterility gene orf108 may not be responsible for the CMS observed in Brassica oxyrrhina and Diplotaxis catholica. Furthermore, we propose the potential coincidence of CMS in alloplasmic lines. Our findings lay the foundation for further elucidation of male sterility gene.

Keywords: Alloplasmic male sterility; Brassica juncea; Male sterility gene; Mitochondrial genome; RNA editing

DOI: https://doi.org/10.1186/s12864-019-5721-2

Plant Cell Physiol. 2019 May 10. pii: pcz083. [Epub ahead of print]

Maize Empty pericarp602 encodes a P-type PPR protein that is essential for seed development.

Zhenjing Ren, Kaijian Fan, Ting Fang, Jiaojiao Zhang, Li Yang, Jianhua Wang, Guoying Wang, Yunjun Liu.

PPR (pentatricopeptide repeat) proteins play crucial roles in intron splicing, which is important for RNA maturation. Identification of novel PPR protein with the function of intron splicing would help to understand the RNA splicing mechanism. In this study, we identified the maize empty pericarp602 (emp602) mutants, the mature kernels of which showed empty pericarp phenotype. We cloned the Emp602 gene from emp602 mutants and revealed that Emp602 encodes a mitochondrial-localized P-type PPR protein. We further revealed that Emp602 is specific for the cis-splicing of mitochondrial Nad4 intron 1 and intron 3, and mutation of Emp602 led to the loss of mature Nad4 transcripts. The loss of function of Emp602 nearly damaged the assembly and accumulation of complex I and arrested mitochondria formation, which arrested the seed development. The failed assembly of complex I triggers significant up-regulation of Aox expression in emp602 mutants. Transcriptome analysis showed that the expression of mitochondrial-related genes, e.g. the genes associated with mitochondrial inner membrane presequence translocase complex and electron carrier activity, were extensively upregulated in emp602 mutant. These results demonstrate that EMP602 functions in the splicing of Nad4 intron 1 and intron 3, and the loss of function of Emp602 arrested maize seed development by disrupting the mitochondria complex I assembly.

Keywords: EMP602; Maize; Nad4; PPR protein; intron splicing; seed development

DOI: https://doi.org/10.1093/pcp/pcz083

Plant Reprod. 2019 May 08.

Identification of a role for an E6-like 1 gene in early pollen-stigma interactions in Arabidopsis thaliana.

Jennifer Doucet, Christina Truong, Elizabeth Frank-Webb, Hyun Kyung Lee, Anna Daneva, Zhen Gao, Moritz K Nowack, Daphne R Goring.

KEY MESSAGE: We describe a function for a novel Arabidopsis gene, E6-like 1 (E6L1), that was identified as a highly expressed gene in the stigma and plays a role in early post-pollination stages. In Arabidopsis, successful pollen-stigma interactions are dependent on rapid recognition of compatible pollen by the stigmatic papillae located on the surface of the pistil and the subsequent regulation of pollen hydration and germination, and followed by the growth of pollen tubes through the stigma surface. Here we have described the function of a novel gene, E6-like 1 (E6L1), that was identified through the analysis of transcriptome datasets, as one of highest expressed genes in the stigma, and furthermore, its expression was largely restricted to the stigma and trichomes. The first E6 gene was initially identified as a highly expressed gene during cotton fiber development, and related E6-like predicted proteins are found throughout the Angiosperms. To date, no orthologous genes have been assigned a biological function. Both the Arabidopsis E6L1 and cotton E6 proteins are predicted to be secreted, and this was confirmed using an E6L1:RFP fusion construct. To further investigate E6L1's function, one T-DNA and two independent CRISPR-generated mutants were analyzed for compatible pollen-stigma interactions, and pollen hydration, pollen adhesion, and seed set were mildly impaired for the e6l1 mutants. This work identifies E6L1 as a novel stigmatic factor that plays a role during the early post-pollination stages in Arabidopsis.

Keywords: BAR expression angler; Compatible pollinations; E6 protein; Pistil; Pollen; Stigma; Transcriptome datasets

DOI: https://doi.org/10.1007/s00497-019-00372-x

Mol Phylogenet Evol. 2019 May 03. pii: S1055-7903(19)30127-7. [Epub ahead of print]

Nuclear and plastid DNA phylogeny of tribe Cardueae (Compositae) with Hyb-Seq data: A new subtribal classification and a temporal diversification framework.

Sonia Herrando-Moraira, Juan Antonio Calleja, Mercè Galbany-Casals, Núria Garcia-Jacas, Jian-Quan Liu, Javier López-Alvarado, Jordi López-Pujol, Jennifer R Mandel, Sergi Massó, Noemí Montes-Moreno, Cristina Roquet, Llorenç Sáez, Alexander Sennikov, Alfonso Susanna, Roser Vilatersana.

Classification of tribe Cardueae in natural subtribes has always been a challenge due to the lack of support of some critical branches in previous phylogenies based on traditional Sanger markers. With the aim to propose a new subtribal delimitation, we applied a Hyb-Seq approach to a set of 76 Cardueae species representing all subtribes and informal groups defined in the tribe, targeting 1061 nuclear conserved orthology loci (COS) designed for Compositae and obtaining chloroplast coding regions as by-product of off-target reads. For the extraction of the target nuclear data, we used two strategies, PHYLUCE and HybPiper, and 776 and 1055 COS loci were recovered with each of them, respectively. Additionally, 87 chloroplast genes were assembled and annotated. With three datasets, phylogenetic relationships were reconstructed using both concatenation and coalescent approaches. Phylogenetic analyses of the nuclear datasets fully resolved virtually all nodes with very high support. Nuclear and plastid tree topologies are mostly congruent with a very limited number of incongruent nodes. Based on the well-solved phylogenies obtained, we propose a new taxonomic scheme of 12 monophyletic and morphologically consistent subtribes: Carlininae, Cardopatiinae, Echinopsinae, Dipterocominae (new), Xerantheminae (new), Berardiinae (new), Staehelininae (new), Onopordinae (new), Carduinae (redelimited), Arctiinae (new), Saussureinae (new), and Centaureinae. In addition, we further updated the temporal framework for origin and diversification of these subtribes. Our results highlight the power of Hyb-Seq over Sanger sequencing of a few DNA markers in solving phylogenetic relationships of traditionally difficult groups.

Keywords: Asteraceae; COS targets; Phylogenomics; Subtribes; Systematics; Target enrichment

DOI: https://doi.org/10.1016/j.ympev.2019.05.001

BMC Genomics. 2019 May 07. 20(1): 343

A high-density genetic map developed by specific-locus amplified fragment (SLAF) sequencing and identification of a locus controlling anthocyanin pigmentation in stalk of Zicaitai (Brassica rapa L. ssp. chinensis var. purpurea).

Gui-Hua Li, Han-Cai Chen, Jia-Li Liu, Wen-Long Luo, Da-Sen Xie, Shao-Bo Luo, Ting-Quan Wu, Waheed Akram, Yu-Juan Zhong.

BACKGROUND: Caixin and Zicaitai (Brassica rapa) belong to Southern and Central China respectively. Zicaitai contains high amount of anthocyanin in leaf and stalk resulting to the purple color. Stalk is the major edible part and stalk color is an economically important trait for the two vegetables. The aim of this study is to construct a high density genetic map using the specific length amplified fragment sequencing (SLAF-seq) technique to explore genetic basis for anthocyanin pigmentation traits via quantitative trait loci (QTL) mapping.
RESULTS: We constructed a high generation linkage map with a mapping panel of F2 populations derived from 150 individuals of parental lines "Xianghongtai 01" and "Yinong 50D" with purple and green stalk respectively. The map was constructed containing 4253 loci, representing 10,940 single nucleotide polymorphism (SNP) markers spanning 1030.04 centiMorgans (cM) over 10 linkage groups (LGs), with an average distance between markers of 0.27 cM. Quantitative trait loci (QTL) analysis revealed that a major locus on chromosome 7 and 4 minor QTLs explaining 2.69-61.21% of phenotypic variation (PVE) were strongly responsible for variation in stalk color trait. Bioinformatics analysis of the major locus identified 62 protein-coding genes. Among the major locus, there were no biosynthetic genes related to anthocyanin. However, there were several transcription factors like helix-loop-helix (bHLH) bHLH, MYB in the locus. Seven predicted candidate genes were selected for the transcription level analysis. Only bHLH49 transcription factor, was significantly higher expressed in both stalks and young leaves of Xianghongtai01 than Yinong50D. An insertion and deletion (InDel) marker developed from deletion/insertion in the promoter region of bHLH49 showed significant correlation with the stalk color trait in the F2 population.
CONCLUSION: Using the constructed high-qualified linkage map, this study successfully identified QTLs for stalk color trait. The identified valuable markers and candidate genes for anthocyanin accumulation in stalk will provide useful information for molecular regulation of anthocyanin biosynthesis. Overall our findings will lay a foundation for functional gene cloning, marker-assisted selection (MAS) and molecular breeding of important economic traits in B. rapa.

Keywords: Brassica rapa; Candidate gene; Genetic map; SLAF-seq; Stalk color

DOI: https://doi.org/10.1186/s12864-019-5693-2