bims-plasge Biomed News
on Plastid genes
Issue of 2019‒07‒28
two papers selected by
Vera S. Bogdanova
Institute of Cytology and Genetics, Siberian Branch of the Russian Academy of Sciences

  1. Plant J. 2019 Jul 19.
      The wild tomato relative Solanum sitiens is a xerophyte endemic to the Atacama Desert of Chile and a potential source of genes for tolerance to drought, salinity, and low temperature stresses. However, until recently, strong breeding barriers prevented its hybridization and introgression with cultivated tomato, Solanum lycopersicum L. We overcame these barriers using embryo rescue, bridging lines, and allopolyploid hybrids, and synthesized a library of introgression lines (ILs) that captures the genome of S. sitiens in the background of cultivated tomato. The IL library consists of 56 overlapping introgressions that together represent ca. 93% of the S. sitiens genome: 65% in homozygous and 28% in heterozygous (segregating) ILs. The breakpoints of each segment and the gaps in genome coverage were mapped by SNP genotyping using the SolCAP SNP array. Marker assisted selection was used to backcross selected introgressions into tomato, to recover a uniform genetic background, to isolate recombinant sublines with shorter introgressions, and to select homozygous genotypes. Each IL contains a single S. sitiens chromosome segment, defined by markers, in the genetic background of cv. NC 84173, a fresh market inbred line. Large differences were observed between the lines for both qualitative and quantitative morphological traits, suggesting the ILs contain highly divergent allelic variation. Several loci contributing to unilateral incompatibility or hybrid necrosis were mapped with the lines. This IL population will facilitate studies of the S. sitiens genome and expands the range of genetic variation available for tomato breeding and research. This article is protected by copyright. All rights reserved.
    Keywords:   Solanum sitiens ; homeologous recombination; hybrid incompatibility; tomato; unilateral incompatibility; wide hybridization
  2. J Integr Plant Biol. 2019 Jul 23.
      In land plants, cytidine-to-uridine (C-to-U) editing of organellar transcripts is an important post-transcriptional process, which is considered to remediate DNA genetic mutations to restore the coding of functional proteins. Pentatricopeptide repeat (PPR) proteins have key roles in C-to-U editing. Owing to its large number, however, the biological functions of many PPR proteins remain to be identified. Through characterizing a small kernel4 (smk4) mutant, here we report the function of Smk4 and its role in maize growth and development. Null mutation of Smk4 slows plant growth and development, causing small plants, delayed flowering time, and small kernels. Cloning revealed that Smk4 encodes a new E-subclass PPR protein, and localization indicated that SMK4 is exclusively localized in mitochondria. Loss of Smk4 function abolishes C-to-U editing at position 1489 of the cytochrome c oxidase1 (cox1) transcript, causing an amino acid change from serine to proline at 497 in Cox1. Cox1 is a core component of mitochondrial complex IV. Indeed, complex IV activity is reduced in the smk4, along with drastically elevated expression of alternative oxidases (AOX). These results indicate that SMK4 functions in the C-to-U editing of cox1-1489, and this editing is crucial for mitochondrial complex IV activity, plant growth, and kernel development in maize. This article is protected by copyright. All rights reserved.