bims-plasge Biomed News
on Plastid Genes
Issue of 2018‒04‒29
five papers selected by
Vera S. Bogdanova
Institute of Cytology and Genetics, Siberian Branch of the Russian Academy of Sciences

  1. Mol Phylogenet Evol. 2018 Apr 18. pii: S1055-7903(17)30396-2. [Epub ahead of print]
      Genomic data are a powerful tool for elucidating the processes involved in the evolution and divergence of species. The speciation and phylogenetic relationships among Chinese Juglans remain unclear. Here, we used results from phylogenomic and population genetic analyses, transcriptomics, Genotyping-By-Sequencing (GBS), and whole chloroplast genomes (Cp genome) data to infer processes of lineage formation among the five native Chinese species of the walnut genus (Juglans, Juglandaceae), a widespread, economically important group. We found that the processes of isolation generated diversity during glaciations, but that the recent range expansion of J. regia, probably from multiple refugia, led to hybrid formation both within and between sections of the genus. In southern China, human dispersal of J. regia brought it into contact with J. sigillata, which we determined to be an ecotype of J. regia that is now maintained as a landrace. In northern China, walnut hybridized with a distinct lineage of J. mandshurica to form J. hopeiensis, a controversial taxon (considered threatened) that our data indicate is a horticultural variety. Comparisons among whole chloroplast genomes and nuclear transcriptome analyses provided conflicting evidence for the timing of the divergence of Chinese Juglans taxa. J. cathayensis and J. mandshurica are poorly differentiated based our genomic data. Reconstruction of Juglans evolutionary history indicate that episodes of climatic variation over the past 4.5 to 33.80 million years, associated with glacial advances and retreats and population isolation, have shaped Chinese walnut demography and evolution, even in the presence of gene flow and introgression.
    Keywords:  Gene introgression; Hybridization speciation; Juglans; Phylogeography; Population genetic
  2. Trends Plant Sci. 2018 Apr 18. pii: S1360-1385(18)30079-7. [Epub ahead of print]
      Root evolution has resulted in the extant bifurcating roots in lycophytes, adventitious/lateral roots in euphyllophytes (ferns and seed plants), and primary roots in seed plants. Here, we hypothesize a role for intermediate-clade-WUSCHEL-RELATED HOMEOBOX (IC-WOX) genes in root evolution. IC-WOX might not be specifically involved in lycophyte bifurcation rooting. In the fern Ceratopteris richardii, IC-WOX is expressed in adventitious/lateral root founder cells. In the seed plant Arabidopsis thaliana, there are two IC-WOX subclades, AtWOX11/12 and AtWOX8/9, in adventitious and primary root founder cells, respectively. Thus, IC-WOX was recruited in the common ancestor of ferns and seed plants for adventitious/lateral root organogenesis and evolved into two subclades in seed plants: one was retained in adventitious root organogenesis, while the other was recruited for primary root organogenesis.
    Keywords:  WOX; root evolution; root founder cell
  3. Genomics. 2018 Apr 18. pii: S0888-7543(18)30245-3. [Epub ahead of print]
      Our understanding of gene regulation is constantly evolving. It is now clear that the majority of cellular transcripts are non-coding RNAs. The spectrum of non-coding RNAs is diverse and includes short (<200 nt) and long non-coding RNAs (lncRNAs) (>200 nt). LncRNAs regulate gene expression through diverse mechanisms. In this review, we describe the emerging roles of lncRNA mediated plant gene regulation. We discuss the current classification of lncRNAs and their role in genome organization and gene regulation. We also highlight a subset of lncRNAs that are epigenetic regulators of plant gene expression. Lastly, we provide an overview of emerging techniques and databases that are employed for the identification and characterization of plant lncRNAs.
    Keywords:  Gene regulation; LncRNA; Non-coding RNA; RNA-seq
  4. Plant J. 2018 Apr 22.
      Drought is the most serious abiotic stress, which causes crop losses on worldwide scale. The present study identified a previously unknown microRNA (designated as hvu-miRX) of 21 nucleotides (nt) in barley. Its precursor (designated pre-miRX) and primary transcript (designated pri-miRX) were also identified, with lengths of 73 nt and 559 nt, respectively. The identified upstream sequence of pri-miRX contains both the TATA box and the CAAT box, which are both required for transcription initiation. Transient promoter activation assays showed that the core promoter region of pri-miRX ranged 500 nt from the transcription start site. In transgenic barley over-expressing the wheat DREB3 transcription factor (TaDREB3) caused hvu-miRX to be highly expressed as compared to the same miRNA in non-transgenic barley. However, the high expression was not directly associated with TaDREB3. Genomic analysis revealed that the hvu-miRX gene was a single copy located on the short arm of chromosome 2 and appeared to be only conserved in Triticeae, but not in other plant species. Notably, transgenic barley overexpressing hvu-miRX showed drought tolerance. Degradome library analysis and other tests showed that hvu-miRX targeted various genes including transcription factors via the cleavage mode. Our data open an excellent opportunity to develop drought stress tolerant cereals with hvu-miRX. This article is protected by copyright. All rights reserved.
    Keywords:  drought tolerance; miRNA precursors; miRNA promoter; novel miRNA; transgenic barley
  5. Theor Appl Genet. 2018 Apr 21.
      KEY MESSAGE: Map-based cloning identified a candidate gene for resistance to the anthracnose fungal pathogen Colletotrichum orbiculare in cucumber, which reveals a novel function for the highly conserved STAYGREEN family genes for host disease resistance in plants. Colletotrichum orbiculare is a hemibiotrophic fungal pathogen that causes anthracnose disease in cucumber and other cucurbit crops. No host resistance genes against the anthracnose pathogens have been cloned in crop plants. Here, we reported fine mapping and cloning of a resistance gene to the race 1 anthracnose pathogen in cucumber inbred lines Gy14 and WI 2757. Phenotypic and QTL analysis in multiple populations revealed that a single recessive gene, cla, was underlying anthracnose resistance in both lines, but WI2757 carried an additional minor-effect QTL. Fine mapping using 150 Gy14 × 9930 recombinant inbred lines and 1043 F2 individuals delimited the cla locus into a 32 kb region in cucumber Chromosome 5 with three predicted genes. Multiple lines of evidence suggested that the cucumber STAYGREEN (CsSGR) gene is a candidate for the anthracnose resistance locus. A single nucleotide mutation in the third exon of CsSGR resulted in the substitution of Glutamine in 9930 to Arginine in Gy14 in CsSGR protein which seems responsible for the differential anthracnose inoculation responses between Gy14 and 9930. Quantitative real-time PCR analysis indicated that CsSGR was significantly upregulated upon anthracnose pathogen inoculation in the susceptible 9930, while its expression was much lower in the resistant Gy14. Investigation of allelic diversities in natural cucumber populations revealed that the resistance allele in almost all improved cultivars or breeding lines of the U.S. origin was derived from PI 197087. This work reveals an unknown function for the highly conserved STAYGREEN (SGR) family genes for host disease resistance in plants.