bims-plasge Biomed News
on Plastid Genes
Issue of 2018‒07‒08
six papers selected by
Vera S. Bogdanova
Institute of Cytology and Genetics, Siberian Branch of the Russian Academy of Sciences

  1. Theor Appl Genet. 2018 Jun 30.
      KEY MESSAGE: Rose morphological traits such as prickles or petal number are influenced by a few key QTL which were detected across different growing environments-necessary for genomics-assisted selection in non-target environments. Rose, one of the world's most-loved and commercially important ornamental plants, is predominantly tetraploid, possessing four rather than two copies of each chromosome. This condition complicates genetic analysis, and so the majority of previous genetic studies in rose have been performed at the diploid level. However, there may be advantages to performing genetic analyses at the tetraploid level, not least because this is the ploidy level of most breeding germplasm. Here, we apply recently developed methods for quantitative trait loci (QTL) detection in a segregating tetraploid rose population (F1 = 151) to unravel the genetic control of a number of key morphological traits. These traits were measured both in the Netherlands and Kenya. Since ornamental plant breeding and selection are increasingly being performed at locations other than the production sites, environment-neutral QTL are required to maximise the effectiveness of breeding programmes. We detected a number of robust, multi-environment QTL for such traits as stem and petiole prickles, petal number and stem length that were localised on the recently developed high-density SNP linkage map for rose. Our work explores the complex genetic architecture of these important morphological traits at the tetraploid level, while helping to advance the methods for marker-trait exploration in polyploid species.
  2. Mol Plant. 2018 Jun 27. pii: S1674-2052(18)30193-X. [Epub ahead of print]
      Plants maintain the ability to form lateral appendages throughout their life cycle and form leaves as the principal lateral appendages of the stem. Leaves initiate at the peripheral zone of the shoot apical meristem, then develop into flattened structures. In most plants, the leaf functions as a solar panel, where photosynthesis converts carbon dioxide and water into carbohydrates and oxygen. To produce structures that can optimally fulfil this function, plants precisely regulate the initiation, shape, and polarity of leaves. Moreover, leaf development is highly flexible, but follows common themes and involves conserved regulatory mechanisms. Leaves may have evolved from lateral branches that converted into determinate, flattened structures. Many other plant parts, such as the floral organs, are considered specialized leaves, and thus leaf development underlies their morphogenesis. Here, we review recent advances in the understanding of how three-dimensional leaf forms are established. We focus on how genes, phytohormones, and mechanical properties modulate leaf development, discussing this in the context of leaf initiation, polarity establishment and maintenance, leaf flattening, and intercalary growth.
    Keywords:  Leaf; blastozone; lateral organ; meristem; morphogenesis; shoot
  3. Trends Plant Sci. 2018 Jun 27. pii: S1360-1385(18)30131-6. [Epub ahead of print]
      Seed evolution is often presented as the evolution of morphological complexity. Following the steps of Wilhelm Hofmeister, I argue that changes in the development of one tissue, the megasporangium/nucellus, can explain the origin of the seed habit. Here, I lay down a 'simpler' story that correlates seed evolution to nucellus cell fate.
    Keywords:  Seed evolution; fertilization; heterospory; nucellus; ovule; spore
  4. New Phytol. 2018 Jun 30.
      The accumulation of anthocyanins in response to specific developmental cues or environmental conditions plays a vital role in plant development and protection against stresses. Extensive research has examined the regulation of anthocyanin biosynthetic genes at the transcriptional and post-transcriptional levels, but the role of chromatin in this regulation remains unknown. Chromatin immunoprecipitation and quantitative reverse transcription-polymerase chain reaction (qRT-PCR) analyses were performed. Genetic interactions between trimethylation of lysine 4 on histone H3 (H3K4me3) and the chromatin remodeling complex SWR1 in the control of anthocyanin biosynthesis were further studied. In this study, we provide evidence that a conserved histone H2 variant, H2A.Z, negatively regulates anthocyanin accumulation through deposition at a set of anthocyanin biosynthetic genes and consequently represses their expression in Arabidopsis thaliana. Our data indicate that the accumulation of anthocyanin in H2A.Z deposition-deficient mutants is associated with increased H3K4me3, which is required for promotion of the expression of anthocyanin biosynthetic genes. We further provide evidence that H3K4me3 in anthocyanin biosynthetic genes is negatively associated with the presence of H2A.Z. Our results reveal an antagonistic relationship between H2A.Z and H3K4me3 in the regulation of the expression of anthocyanin biosynthesis genes, adding another layer of regulation to anthocyanin biosynthesis genes and highlighting the role of chromatin in gene regulation.
    Keywords:  Arabidopsis chromatin immunoprecipitation; H2A.Z; anthocyanins; lysine 4 on histone H3 (H3K4me3)
  5. Theor Appl Genet. 2018 Jun 30.
      KEY MESSAGE: We identified a novel allele of the Vrn-A3 gene that is associated with an early flowering trait in wheat. This trait is caused by a cis-element GATA box in Vrn-A3. To identify novel flowering genes in wheat, we investigated days from germination to heading (DGH) in tetraploid wheat accessions. We found that the tetraploid variety Triticum turgidum L. ssp. dicoccum (TN26) harbors unknown genes that surpass the earliness effect of the early flowering allele Ppd-A1a harbored by TN28 (T. turgidum L. ssp. turgidum conv. pyramidale). Using recombinant inbred lines resulting from a cross between TN26 and TN28, we performed a quantitative trait locus (QTL) analysis for DGH. We identified a QTL for earliness in TN26 on chromosome 7AS, the chromosome on which Vrn-A3 is located. By sequence analysis for the Vrn-A3 locus in both TN26 and TN28, we identified a 7-bp insertion that included a cis-element GATA box sequence at the promoter region of the Vrn-A3 locus of TN26. Based on an expression analysis using sister lines for Vrn-A3, we suggest that the early flowering trait of TN26 was caused by the GATA box in Vrn-A3. In addition, we identified tetraploid wheat as a useful genetic resource for wheat breeding.
  6. New Phytol. 2018 Jun 30.
      Contents I. II. III. IV. V. References SUMMARY: The floral ground plan is a map of where and when floral organ primordia arise. New results combining the defined phylogeny of flowering plants with extensive character mapping have predicted that the angiosperm ancestor had whorls rather than spirals of floral organs in large numbers, and was bisexual. More confidently, the monocot ancestor likely had three organs in each whorl, whereas the rosid and asterid ancestor (Pentapetalae) had five, with the perianth now divided into sepals and petals. Genetic mechanisms underlying the establishment of the floral ground plan are being deduced using model species, the rosid Arabidopsis, the asterid Antirrhinum, and in grasses such as rice. In this review, evolutionary and genetic conclusions are drawn together, especially considering how known genes may control individual processes in the development and evolution of ground plans. These components include organ phyllotaxis, boundary formation, organ identity, merism (the number or organs per whorl), variation in the form of primordia, organ fusion, intercalary growth, floral symmetry, determinacy and, finally, cases where the distinction between flowers and inflorescences is blurred. It seems likely that new pathways of ground plan evolution, and new signalling mechanisms, will soon be uncovered by integrating morphological and genetic approaches.
    Keywords:  angiosperms; floral boundaries; floral ground plan; floral symmetry; flower evolution; merism; phyllotaxy; primordia