Mitochondrial variation in small brown planthoppers linked to multiple traits and probably reflecting a complex...

Area of Science:

• Evolutionary Biology
• Genetics
• Ecology

Background:

• Mitochondrial genomes are increasingly linked to adaptive evolution in various taxa.
• Establishing direct links between mitochondrial haplotypes and organismal phenotypes remains challenging.
• Mitonuclear discordance in Laodelphax striatellus (SBPH) offers a model for studying climatic adaptation of mitochondrial genomes.

Purpose of the Study:

• To investigate the role of mitochondrial genome evolution in adaptation to cold climates in SBPH.
• To test the hypothesis that a specific mitochondrial haplogroup (HGI) is associated with cold adaptation.
• To explore potential mitonuclear interactions influencing phenotypic traits.

Main Methods:

• Phylogenetic analyses of mitochondrial genomes.
• Population genetic analyses to detect selection.
• Bioassays including chill-coma recovery tests.
• Protein modeling to investigate molecular changes.

Main Results:

• Contrary to the hypothesis, chill-coma recovery and selection tests indicated that haplogroup HGII, not HGI, is involved in cold adaptation.
• Phylogenetic analysis revealed HGII is nested within HGI, possessing three nonsynonymous changes in ND2, ND5, and CYTB.
• These molecular changes in HGII likely enhance mtDNA copy number, cold tolerance, and fecundity, with a key amino acid change M114T in ND2.
• Evidence of mitonuclear epistasis was observed, where nuclear background influenced fecundity and chill recovery.

Conclusions:

• mtDNA variation is linked to organismal-level evolution in SBPH.
• Specific molecular changes in mitochondrial genes (ND2, ND5, CYTB) within HGII may confer cold adaptation.
• Mitonuclear interactions play a role in maintaining mtDNA diversity and influencing phenotypic traits.
• The high frequency of HGI in cold regions remains unexplained, warranting further investigation.