bims-plasge Biomed News
on Plastid genes
Issue of 2020‒03‒01
two papers selected by
Vera S. Bogdanova
Institute of Cytology and Genetics, Siberian Branch of the Russian Academy of Sciences

  1. J Exp Bot. 2020 Feb 27. pii: eraa106. [Epub ahead of print]
      Awns are bristle-like structures formed at the tip of the lemma on the florets of some cereal grasses. Wild-type wheat is awned, but awnletted and awnless variants have been selected and nowadays all forms are cultivated. In this study, we dissected the genetic control underlying variation of this characteristic feature by association mapping in a large panel of 1110 winter wheat cultivars of worldwide origin. We identified the B1 (Tipped 1) locus on chromosome 5A as the major determinant of awnlessness globally. Using a combination of fine-mapping and expression analysis, we identified a putative C2H2 zinc finger protein with an EAR domain, characteristic of transcriptional repressors, as likely candidate for Tipped 1. This gene was found to be up-regulated in awnless B1 compared to awned b1 plants, indicating that mis-expression of this transcriptional regulator may contribute to the reduction of awn length in B1 plants. Taken together, our study provides an entry point towards a better molecular understanding of the evolution of morphological features in cereals through selection and breeding.
    Keywords:   B1 ; Tipped 1 ; Triticum aestivum; association mapping; awns; mis-expression; wheat
  2. Theor Appl Genet. 2020 Feb 22.
      KEY MESSAGE: The Pseudo-Response Regulator 2 gene was identified in the c1 locus, representing a genetic factor regulating fruit color in pepper using GBS-based BSA-seq. The loci c1, c2, and y have been widely reported as genetic determinants of various ripe fruit colors in pepper. However, c1, which may impact reduced pigmentation in red, orange, and yellow fruits, is not well understood. Two cultivars showing peach or orange fruit in Capsicum chinense 'Habanero' were found to have c2 mutation and were hypothesized to segregate c1 locus in the F2 population. Habanero peach (HP) showed a reduced level of chlorophylls, carotenoids and total soluble solids in immature and ripe fruits. A microscopic examination of the fruit pericarps revealed smaller plastids and less stacked thylakoid grana in HP. The expression of many genes related to chlorophyll and carotenoid biosynthetic pathways were reduced in HP. To identify the genomic region of the c1 locus, bulked segregant analysis combined with genotyping-by-sequencing was employed on an F2 population derived from a cross between Habanero orange and HP. One SNP at chromosome 1 was strongly associated with the peach fruit color. Pepper Pseudo-Response Regulator 2 (PRR2) was located close to the SNP and cosegregated with the peach fruit color. A 41 bp deletion at the third exon-intron junction region of CcPRR2 in HP resulted in a premature termination codon. A nonsense mutation of CaPRR2 was found in C. annuum 'IT158782' which had white ripe fruit coupled with null mutations of capsanthin-capsorubin synthase (y) and phytoene synthase 1 (c2). These results will be useful for the genetic improvement in fruit color and nutritional quality in pepper.