bims-plasge Biomed News
on Plastid genes
Issue of 2021‒11‒14
two papers selected by
Vera S. Bogdanova
Institute of Cytology and Genetics, Siberian Branch of the Russian Academy of Sciences

  1. Theor Appl Genet. 2021 Nov 06.
      KEY MESSAGE: OrDeb2 confers post-attachment resistance to Orobanche cumana and is located in a 1.38 Mbp genomic interval containing a cluster of receptor-like kinase and receptor-like protein genes with nine high-confidence candidates. Sunflower broomrape is a holoparasitic angiosperm that parasitizes on sunflower roots, severely constraining crop yield. Breeding for resistance is the most effective method of control. OrDeb2 is a dominant resistance gene introgressed into cultivated sunflower from a wild-related species that confers resistance to highly virulent broomrape races. The objectives of this study were as follows: (i) locate OrDeb2 into the sunflower genome and determine putative candidate genes and (ii) characterize its underlying resistance mechanism. A segregating population from a cross between the sunflower resistant line DEB2, carrying OrDeb2, and a susceptible line was phenotyped for broomrape resistance in four experiments, including different environments and two broomrape races (FGV and GTK). This population was also densely genotyped with microsatellite and SNP markers, which allowed locating OrDeb2 within a 0.9 cM interval in the upper half of Chromosome 4. This interval corresponded to a 1.38 Mbp genomic region of the sunflower reference genome that contained a cluster of genes encoding LRR (leucine-rich repeat) receptor-like proteins lacking a cytoplasmic kinase domain and receptor-like kinases with one or two kinase domains and lacking an extracellular LRR region, which were valuable candidates for OrDeb2. Rhizotron and histological studies showed that OrDeb2 determines a post-attachment resistance response that blocks O. cumana development mainly at the cortex before the establishment of host-parasite vascular connections. This study will contribute to understand the interaction between crops and parasitic weeds, to establish durable breeding strategies based on genetic resistance and provide useful tools for marker-assisted selection and OrDeb2 map-based cloning.
  2. Plant J. 2021 Nov 07.
      In the chloroplast, OZ1 is a RanBP2-type zinc finger protein required for many RNA editing events, a process by which specific cytosines are enzymatically converted to uracils as a correction mechanism for missense mutations in the organelle genomes. RNA editing is carried out by a large multi-protein complex called the "editosome" that contains members of the PPR protein family, the RIP/MORF family, and the ORRM family in addition to OZ1. OZ1 is an 82-kDa protein with distinct domains, including a pair of zinc finger domains and a unique C-terminal region. To elucidate the functions of these domains, we have generated truncations of OZ1 for use in protein-protein interaction assays that identified the C-terminal region of OZ1 as well as the zinc finger domains as the primary interactors with PPR proteins, which are factors required for site-specificity and enzymatic editing. Expression of these OZ1 truncations in vivo showed that the zinc finger domains were required to restore chloroplast RNA editing in oz1 knockout plants. Mutation of key structural residues in the zinc finger domains showed that they are necessary for editing and required for interaction with ORRM1, a general editing factor with an RNA-binding domain. These functional characterizations of the zinc fingers and novel C-terminal domain contribute to our understanding of the model for the chloroplast plant editosome.
    Keywords:  RNA editing; chloroplast; plant editosome; zinc finger