bims-plasge 2023-09-17 papers

Issue of 2023–09–17
two papers selected by
Vera S. Bogdanova, ИЦиГ СО РАН

Plant Cell Physiol. 2023 Sep 13. pii: pcad104. [Epub ahead of print]

Plastid inheritance revisited: emerging role of organelle DNA degradation in angiosperms.

Plastids are essential organelles in angiosperms and show non-Mendelian inheritance due to their evolution as endosymbionts. In approximately 80% of angiosperms, plastids are thought to be inherited from the maternal parent, whereas other species transmit plastids biparentally. Maternal inheritance can be generally explained by the stochastic segregation of maternal plastids after fertilization because the zygote is overwhelmed by the maternal cytoplasm. In contrast, biparental inheritance shows transmission of organelles from both parents. In some species, maternal inheritance is not absolute and paternal leakage occurs at a very low frequency (~10-5). A key process controlling the inheritance mode lies in the behavior of plastids during male gametophyte (pollen) development, with accumulating evidence indicating that the plastids themselves or their DNAs are eliminated during pollen maturation or at fertilization. Cytological observations in numerous angiosperm species have revealed several critical steps that mutually influence the degree of plastid transmission quantitatively among different species. This review revisits plastid inheritance and focuses on the mechanistic viewpoint. Particularly, we focus on a recent finding demonstrating that both low temperature and plastid DNA degradation mediated by the organelle exonuclease DPD1 influence the degree of paternal leakage significantly in tobacco. Given these findings, we also highlight the emerging role of DPD1 in organelle DNA degradation.

Keywords: Biparental and maternal inheritance; DPD1 (DEFECTIVE IN POLLEN ORGANELLE DNA DEGRADATION1); Nuclease; Plastid inheritance; Pollen

DOI: https://doi.org/10.1093/pcp/pcad104

Front Plant Sci. 2023 ;14 1233280

A hypervariable intron of the STAYGREEN locus provides excellent discrimination among Pisum fulvum accessions and reveals evidence for a relatively recent hybridization event with Pisum sativum.

N F Weeden, M Lavin, S Abbo, C J Coyne, K McPhee.

An analysis of 82 non-synonymous Pisum fulvum accessions for sequence variation in a fragment of the STAYGREEN (SGR) locus revealed 57 alleles, most of which differed in indel structure. Eight additional P. fulvum accessions, each supposedly synonymous with a different accession of the initial group, were also analyzed. In every case the paired synonymous accessions possessed the same SGR sequence but varied slightly for a 6-trait morphological phenotype, indicating that SGR sequence is a much more reliable indicator of accession identity than is a morphological characterization. SGR sequence analysis confirmed our previous finding that P. fulvum accessions separate into two allele groups. This division was not supported by results of previous studies that were based on sequences distributed across the entire genome, suggesting that the division may have been produced by selection at a nearby locus and that the SGR phylogeny may not be good indicator of overall relationships within the species. One P. fulvum accession, PI 595941 (=JI1796), displayed an SGR sequence outside the variation typical of the species. Instead, its allele resembled alleles limited to a set of Pisum sativum landraces from the Middle East, suggesting hybridization between ancestors of PI 595941 and some primitive form of domesticated P. sativum. With one exception from the extreme northwest corner of Israel, P. fulvum accessions collected north of latitude 35.5° N were fixed for alleles from group A. These northern accessions also displayed greatly reduced SGR sequence diversity compared to group A accessions collected from other regions, suggesting that the northern populations may represent recent extensions of the range of the species. Group B accessions were distributed from Lake Tiberias south and were generally sympatric with the southern group A accessions. Although group B accessions occupied a smaller area than group A, the SGR sequence diversity in this group (28 alleles in 33 accessions) exceeded that for group A.

Keywords: gene phylogeny; genetic diversity; interspecific hybridization; intron variability; repetitive DNA

DOI: https://doi.org/10.3389/fpls.2023.1233280