Despite the significant progress that has been made in the genome sequencing of Beauveria species, mitochondrial genome (mitogenome) used to examine genetic diversity within fungal populations. Complete mitogenomes of Beauveria species can be easily sequenced and assembled using various sequencing techniques. However, since mitogenome annotations are mainly derived from similar species comparison and software prediction, and are not supported by RNA-seq transcripts data, it leads to problems with the accuracy of mitochondrial annotations and the inability to understand RNA processing. In this study, we assembled and annotated the mitogenome of eight Beauveria strains using Illumina DNA and RNA sequencing data. The circular mitogenome of eight Beauveria strains ranged from 26,850 bp (B. caledonica strain ATCC 64970) to 35,999 bp (B. brongniartii strain GYU-BMZ03), with the intronic insertions accounting for most of the size variation, thus contributing to a total mitochondrial genome (mitogenome) size of 7.01% and 28.95%, respectively. Intron number variations were not directly related to the evolutionary relationship distance. Besides ribosomal protein S3 (rps3), most introns are lost too quickly and lack the stability of protein-coding genes. The short RNA-seq reads from next-generation sequencing can improve the mitochondrial annotation accuracy and help study polycistronic transcripts and RNA processing. The transcription initiation sites may be located in the control region. Most introns do not serve as taxonomic markers and also lack open reading frames (ORFs). We assumed that the poly A tail was added to the polycistronic transcript before splicing and one polycistronic transcript (trnM(1)-trnL(1)-trnA-trnF-trnK-trnL(2)-trnQ-trnH-trnM(2)-nad2-nad3-atp9-cox2-trnR(1)-nad4L-nad5-cob-trnC-cox1-trnR(2)-nad1-nad4-atp8-atp6-rns-trnY-trnD-trnS-trnN-cox3-trnG-nad6-trnV-trnI-trnS-trnW-trnP-rnl(rps3)-trnT-trnE-trnM(3)) was first processed from the mitogenome and was subsequently processed into smaller mono-, di-, or tricistronic RNAs.
Rhizobium lipopolysaccharide (LPS) is an important component of the cell wall of gram-negative bacteria and serves as a signal molecule on the surface of rhizobia, participating in the symbiosis during rhizobia–legume interaction. In this study, we constructed a deletion mutant of ADP-L-glycerol-D-mannoheptosyl-6-exoisomerase (rfaD) of Mesorhizobium huakuii 7653R and a functional complementary strain. The results showed that the deletion of rfaD did not affect the free-living growth rate of 7653R, but that it did affect the LPS synthesis and that it increased sensitivity to abiotic stresses. The rfaD promoter-GUS reporter assay showed that the gene was mainly expressed in the infection zone of the mature nodules. The root nodules formation of the rfaD mutant was delayed during symbiosis with the host plant of Astragalus sinicus. The symbiotic phenotype analyses showed that the nodules of A. sinicus lost symbiotic nitrogen fixation ability, when inoculated with the rfaD mutant strain. In conclusion, our results reveal that the 7653R rfaD gene plays a crucial role in the LPS synthesis involved in the symbiotic interaction between rhizobia and A. sinicus. This study also provides new insights into the molecular mechanisms by which the rhizobia regulate their own gene expression and cell wall components enabling nodulation in legumes.
The little-known genus Pseudoechthistatus Pic, 1917 belongs to the subfamily Lamiinae of the family Cerambycidae. Adult Pseudoechthistatus hei Xie and W. Wang, 2019 specimens were collected from Bāijì Hill, Xīntángfáng Village, Wéixī County, Yúnnán Province, China. The complete mitochondrial genome (GenBank accession number: ON641973.1) of P. hei was sequenced, annotated, and characterized; it is a circular DNA molecule of 16,103 bp with a 75.71% AT content, and it comprised 13 protein-coding genes (PCG), 22 tRNA genes, two rRNA genes, and 1 control region. The PCGs initiated with the typical ATN (Met) start codons, and were terminated by typical TAN stop codons. The Bayesian Inference phylogenetic tree was first constructed using JTT + F + I + G4 model for P. hei , which showed that P. hei was closely related to Monochamus alternatus alternatus .
The genus Mastax Fischer von Waldheim 1827 belongs to the family Carabidae. Specimens of adult Mastax latefasciata Liebke, 1931 were collected from Yājì Hill, Huáihuà City, Húnán Province, China. The complete mitochondrial genome (GenBank accession number ON674050.1) of M. latefasciata was sequenced, annotated, and characterized. The results showed that it was a circular DNA molecule of 16,735 bp with 81.07% AT content and comprised 13 protein-coding genes (PCG), 22 tRNA genes, 2 rRNA genes, and 1 control region. The PCGs were initiated using typical ATN (Met) and TTG (Met) start codons and terminated using typical TAN stop codons. The phylogenetic position of Mastax within the Carabidae was first evaluated using complete mitogenomes, and the results showed that it was close to Cicindela anchoralis and Manticora tibialis .
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