Organelle genome fragmentation has been found in a wide range of eukaryotic lineages; however, its use in phylogenetic reconstruction has not been demonstrated. We explored the use of mitochondrial (mt) genome fragmentation in resolving the controversial suborder-level phylogeny of parasitic lice (order Phthiraptera). There are ∼5,000 species of parasitic lice in four suborders (Amblycera, Ischnocera, Rhynchophthirina and Anoplura), which infest mammals and birds. The phylogenetic relationships among these suborders are unresolved despite decades of studies. We sequenced the mt genomes of eight species of parasitic lice and compared them with 17 other species of parasitic lice sequenced previously. We found that the typical single-chromosome mt genome is retained in the lice of birds but fragmented into many minichromosomes in the lice of eutherian mammals. The shared derived feature of mt genome fragmentation unites the eutherian mammal lice of Ischnocera (family Trichodectidae) with Anoplura and Rhynchophthirina to the exclusion of the bird lice of Ischnocera (family Philopteridae). The novel clade, namely Mitodivisia, is also supported by phylogenetic analysis of mt genome and cox1 gene sequences. Our results demonstrate, for the first time, that organelle genome fragmentation is informative for resolving controversial high-level phylogenies.
A yellow green peel mutant (ygp) in cucumber was caused by a mutation in Csa2G352940 encoding MYB36 transcription factor. Peel color is one of the important agronomic traits of cucumber (Cucumis sativus L.). However, studies on the molecular regulation mechanism of peel color in cucumber are few. In this study, a cucumber yellow green peel mutant (ygp) of cucumber mutagenized with ethylmethylsulfone by using a wild type cucumber with dark green peel was identified. Pigment measurements indicated that the chlorophyll content of the ygp mutant was less than that of the wild type. Genetic analysis revealed that the phenotype of the ygp mutant was monogenic recessive inheritance. MutMap and genotyping results demonstrated that Csa2G352940 (CsMYB36), encoding the transcription factor MYB36, was the causal gene of the ygp mutant in cucumber. CsMYB36 was downregulated in the fruit of the ygp mutant. Transcriptome profile analysis of the fruit peel of the ygp mutant identified 92 candidate genes including genes that encode Casparian strip (CsCASP1) and pigment synthesis protein (CsMYC2) involved in peel color development in cucumber. CsMYB36 may regulate yellow green coloration in cucumber by interacting with these genes. Overall, these results showed that CsMYB36 can regulate the yellow green peel coloration in cucumber.
Animal mitochondrial (mt) genomes are typically double-strand circular DNA molecules, but diverse structural variations have been widely found in multiple groups. In parasitic lice (Phthiraptera), the structure of mt genomes varies remarkably across all five suborders. In this study, we reported the complete mt genome of a chicken body louse, Menacanthus cornutus, which has a typical single circular mt chromosome and drastic mt gene rearrangements. This mt genome is 15,693 bp in length, consisting of 13 protein-coding genes, 23 tRNA genes, 2 rRNA genes, and a control region. A comparison with a typical insect mt genome suggested that two highly similar trnM are present in the mt genome of M. cornutus. Moreover, almost every single gene was rearranged, and over half of mt genes were inverted. Phylogenetic analyses inferred from the mt genome sequences supported the monophyly and position of Amblycera. Mapped over the phylogenetic relationships of Amblycera, we identified two inversion events for the conserved gene blocks in Boopidae and Menoponidae. The inverted ND4L-ND4 was likely a synapomorphic rearrangement in Menoponidae. Our study demonstrated the importance of sequencing mt genomes for additional taxa to uncover the mechanism underlying the structural evolution of the mt genome in parasitic lice.
SUMMARYTo improve our understanding of the mechanism underlying cucumber glossiness regulation, a novel cucumber mutant with a glossy peel (Csgp) was identified. MutMap, genotyping, and gene editing results demonstrated that CsSEC23, which is the core component of COPII vesicles, mediates the glossiness of cucumber fruit peel. CsSEC23 is functionally conserved and located in the Golgi and endoplasmic reticulum. CsSEC23 could interact with CsSEC31, but this interaction was absent in the Csgp mutant, which decreased the efficiency of COPII vesicle transportation. Genes related to wax and cutin transport were upregulated in the Csgp mutant, and the cuticle structure of the Csgp‐mutant peel became thinner. Moreover, the wax and cutin contents were also changed due to CsSEC23 mutation. Taken together, the results obtained from this study revealed that CsSEC23 mediates cucumber glossiness, and this mediating might be affected by COPII vesicle transportation.
The complete mitochondrial genome (mitogenome) of Tropidothorax sinensis (Reuter, 1888) was determined in the present study by using high-throughput sequencing. This mitogenome is 15,422 bp in size and comprises 37 typical coding genes and a control region. All protein-coding genes are initiated with ATN, except for COX1 and ND4L use TTG as the start codon, and terminate with TAA or TAG with the exception of COX2 , COX3 and ND1 which use a single T residue as the stop codon. Twenty-one of the 22 transfer RNA genes have the typical clover-leaf structure except for tRNA Ser(AGN) . The monophyly of the family Lygaeidae and the sister relationship between T. sinensis and T. cruciger is supported by maximum likelihood analysis based on the protein-coding and ribosomal RNA gene sequences.
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