bims-plasge Biomed News
on Plastid genes
Issue of 2019‒02‒24
four papers selected by
Vera S. Bogdanova
Institute of Cytology and Genetics, Siberian Branch of the Russian Academy of Sciences

  1. Plant Mol Biol. 2019 Feb 20.
      KEY MESSAGE: Grain amyloplast and leaf chloroplast DNA sequences are identical in rice plants but are differentially methylated. The leaf chloroplast DNA becomes more methylated as the rice plant ages. Rice is an important crop worldwide. Chloroplasts and amyloplasts are critical organelles but the amyloplast genome is poorly studied. We have characterised the sequence and methylation of grain amyloplast DNA and leaf chloroplast DNA in rice. We have also analysed the changes in methylation patterns in the chloroplast DNA as the rice plant ages. Total genomic DNA from grain, old leaf and young leaf tissues were extracted from the Oryza sativa ssp. indica cv. MR219 and sequenced using Illumina Miseq. Sequence variant analysis revealed that the amyloplast and chloroplast DNA of MR219 were identical to each other. However, comparison of CpG and CHG methylation between the identical amyloplast and chloroplast DNA sequences indicated that the chloroplast DNA from rice leaves collected at early ripening stage was more methylated than the amyloplast DNA from the grains of the same plant. The chloroplast DNA became more methylated as the plant ages so that chloroplast DNA from young leaves was less methylated overall than amyloplast DNA. These differential methylation patterns were primarily observed in organelle-encoded genes related to photosynthesis followed by those involved in transcription and translation.
    Keywords:  Ageing; Amyloplast; Chloroplast; DNA methylation; Tissue specificity
  2. Front Plant Sci. 2019 ;10 94
      The use of sterility is common in plants and multiple loci for hybrid sterility have been identified in crops such as rice. In soybean, fine-mapping and research on the molecular mechanism of male sterility is limited. Here, we identified a male-sterile soybean line, which produces larger, abnormal pollen grains that stain poorly with I2-KI. In an inheritance test, all F 1 plants were fertile and the F 2 and F 2:3 populations conformed with the expected segregation ratio of 3:1 (fertility:sterility) (p = 0.82) and showed a 1:2:0 ratio of homozygous fertile: heterozygous fertile: homozygous sterile genotypes (p = 0.73), suggesting that the sterility was controlled by a single recessive gene (designated "mst-M"). Bulked segregant analysis showed that almost all single-nucleotide polymorphisms (SNPs; 95.92%) were distributed on chromosome 13 and 868 SNPs (95.81%) were distributed in the physical region of Chromosome 13.21877872 to Chromosome 13.22862641. Genetic mapping revealed that mst-M was flanked by W1 and dCAPS-1 with genetic distances of 0.6 and 1.8 cM, respectively. The order of the consensus markers and known sterility genes was: Satt146 - (5.0 cM) - st5 - (2.5 cM) - Satt030 - (15.3 cM) - ms6 - (5.0 cM) - Satt149 - (39.5 cM) - W1 - (0.6 cM) - mst-M - (14.1 cM) - Satt516 (7.5 cM) - ms1 - (16.3 cM) - Satt595. These results suggest that mst-M is a newly identified male-sterility gene, which represents an alternative genetic resource for developing a hybrid seed production system for soybean.
    Keywords:  abnormal pollen grains; bulked segregant analysis; dCAPS; inheritance test; male sterility
  3. Plant Cell Physiol. 2019 Feb 23. pii: pcz032. [Epub ahead of print]
      Malonyl-ACP is a key building block for the synthesis of fatty acids, which are important components of cell membranes, storage oils, and lipid-signaling molecules. Malonyl CoA-acyl carrier protein (ACP) malonyltransferase (MCAMT) catalyzes the production of malonyl-ACP and CoA from malonyl-CoA and ACP. Here, we report that MCAMT plays a critical role in cell division and has the potential to increase the storage oil content in Arabidopsis. The quantitative RT-PCR and MCAMT promoter:GUS analyses showed that MCAMT is predominantly expressed in shoot and root apical meristems, leaf hydathodes, and developing embryos. The fluorescent signals of MCAMT:eYFP were observed in both chloroplasts and mitochondria of tobacco leaf protoplasts. In particular, the N-terminal region (amino acid residues 1 to 30) of MCAMT was required for mitochondrial targeting. The Arabidopsis mcamt-1 and -2 mutants exhibited an embryo-lethal phenotype because of the arrest of embryo development at the globular stage. The transgenic Arabidopsis expressing antisense MCAMT RNA showed growth retardation caused by the defects in cell division. The overexpression of MCAMT driven by the promoter of the senescence-associated 1 (SEN1) gene, which is predominantly expressed in developing seeds, increased the seed yield and storage oil content of Arabidopsis. Taken together, the plastidial and mitochondrial MCAMT is essential for Arabidopsis cell division and is a novel genetic resource useful for enhancing storage oil content in oilseed crops.
    Keywords:   Arabidopsis thaliana ; Cell division; Malonyl CoA-ACP malonyltransferase; Protein Targeting; and Storage oil
  4. Science. 2019 Feb 22. pii: eaav4467. [Epub ahead of print]363(6429):
      Chloroplasts contain thousands of nucleus-encoded proteins that are imported from the cytosol by translocases in the chloroplast envelope membranes. Proteolytic regulation of the translocases is critically important, but little is known about the underlying mechanisms. We applied forward genetics and proteomics in Arabidopsis to identify factors required for chloroplast outer envelope membrane (OEM) protein degradation. We identified SP2, an Omp85-type β-barrel channel of the OEM, and CDC48, a cytosolic AAA+ (ATPase associated with diverse cellular activities) chaperone. Both proteins acted in the same pathway as the ubiquitin E3 ligase SP1, which regulates OEM translocase components. SP2 and CDC48 cooperated to bring about retrotranslocation of ubiquitinated substrates from the OEM (fulfilling conductance and motor functions, respectively), enabling degradation of the substrates by the 26S proteasome in the cytosol. Such chloroplast-associated protein degradation (CHLORAD) is vital for organellar functions and plant development.