bims-plasge Biomed News
on Plastid genes
Issue of 2021‒04‒11
two papers selected by
Vera S. Bogdanova
Institute of Cytology and Genetics, Siberian Branch of the Russian Academy of Sciences

  1. Plant Cell Physiol. 2021 Apr 07. pii: pcab049. [Epub ahead of print]
      The use of pulses as ingredients for the production of food products rich in plant proteins is increasing. However, protein fractions prepared from pea or other pulses contain significant amounts of saponins, glycosylated triterpenes which can impart an undesirable bitter taste when used as an ingredient in foodstuffs. In this paper, we describe the identification and characterization of a gene involved in saponin biosynthesis during pea seed development, by screening mutants obtained from two Pisum sativum TILLING (Targeting Induced Local Lesions in Genomes) populations in two different genetic backgrounds. The mutations studied are located in a gene designated PsBAS1 (β-amyrin synthase1) which is highly expressed in maturing pea seeds and which encodes a protein previously shown to correspond to an active β-amyrin synthase. The first allele is a nonsense mutation, while the second mutation is located in a splice site and gives rise to a mis-spliced transcript encoding a truncated, non-functional protein. The homozygous mutant seeds accumulated virtually no saponin without affecting seed nutritional or physiological quality. Interestingly, BAS1 appears to control saponin accumulation in all other tissues of the plant examined. These lines represent a first step in the development of pea varieties lacking bitterness off-flavours in their seeds. Our work also shows that TILLING populations in different genetic backgrounds represent valuable genetic resources for both crop improvement and functional genomics.
    Keywords:  DDMP saponin; TILLING; pea; seed quality; β-amyrin synthase
  2. J Exp Bot. 2021 Apr 02. pii: erab142. [Epub ahead of print]
      Fatty acyl reductases (FARs) catalyze the reduction of fatty acyl-coenzyme A (CoA) or -acyl carrier protein (ACP) substrates to primary fatty alcohols, which play essential roles in lipid metabolism in plants. However, the mechanism of FARs involved in male reproduction is poorly defined. Here, we found that two maize allelic mutants, ms25-6065 and ms25-6057, displayed defective anther cuticle, abnormal Ubisch body formation, impaired pollen exine formation and complete male sterility. Based on map-based cloning and CRISPR/Cas9 mutagenesis, Zm00001d048337 was identified as ZmMs25 gene, encoding a plastid-localized FAR with catalytic activities to multiple acyl-CoA substrates in vitro, and four conserved residues (G101, G104, Y327 and K331) of ZmMs25 were critical for its activity. ZmMs25 was predominantly expressed in anther at stage 9, and was directly regulated by transcriptional factor ZmMYB84. Lipidomics analysis revealed that ms25 mutation had significant effects on reducing most of cutin monomers and internal lipids, and altering composition of cuticular wax in anthers. Moreover, loss of ZmMs25 function significantly affected the expression of its four paralogous genes and five cloned lipid metabolic male-sterility genes in maize. These data suggest that ZmMs25 is required for anther development and male fertility, implying its application potential in maize and other crops.
    Keywords:   ZmMs25 ; anther and pollen development; fatty acyl reductase; genic male sterility; maize; transcriptional regulation