Biology subjects

Kuster, S. A.

Publications and source records attributed to Kuster, S. A..

3 recordsLinked to original sources

bioRxiv2025

Plant MutS2 proteins function in plastid ribosome quality control

Tight regulation of chloroplast translation is essential for plant growth, development and environmental response. Active translation can result in stalling and collision of ribosomes, which have negative fitness consequences. However, the ways in which chloroplasts respond to these types of translational stressors remain unknown. Here, we identify two MutS2 proteins that act as critical players in plastid ribosome-associated quality control (RQC) in Arabidopsis. We found that both MutS2A and MutS2B are required to overcome specific antibiotic-induced ribosome stalling and collisions. Further, these proteins appear to be essential for tissue greening during de-etiolation, potentially due to increased translational demand during the transition from etioplast to chloroplast. Although bacterial homologs of MutS2 have been widely recognized for their role in regulating homologous recombination, we found only weak support for this function in Arabidopsis plastids. Therefore, these proteins, which are widely conserved among photosynthetic eukaryotes, appear to be central in the resolution of ribosome collisions and may play a critical role during times of increased translational demand.

plant biology↗

bioRxiv2025

Sensitivity of genome-wide tests for mitonuclear genetic incompatibilities

Mismatches between interacting mitochondrial and nuclear gene products in hybrids have been proposed to disproportionately contribute to early species boundaries. Under this model, genetic incompatibilities emerge when mitochondrial haplotypes are in a cellular context without their coevolved nuclear-encoded mitochondrial (n-mt) proteins. Some case studies have shown that such disruptions in mitonuclear coevolution can contribute to reproductive isolation, but whether mitonuclear incompatibilities generate selection that impacts multiple n-mt loci and/or causes broad, genome-wide contributions to speciation is unclear. Here, we leverage a system with several hybridizing species pairs (Xiphophorus fishes) that have known mitonuclear incompatibilities of large effect. We divided nuclear-encoded genes into three classes based on level of interaction with mitochondrial gene products. We found only inconsistent statistical support for a difference between these classes in the degree of positive covariation in mitonuclear ancestry. We discuss evidence that these analyses are sensitive to the amount of non-synonymous divergence between parent species in interacting n-mt genes or the age of the hybridization event. Overall, our results imply that genome-wide scans focused on enrichment of broad functional gene classes may often be insufficient for detecting a history of mitonuclear coevolution, even when strong selection is acting on mitonuclear incompatibilities at multiple loci.

genomics↗

bioRxiv2024

Expansion of the MutS gene family in plants

The MutS gene family is distributed across the tree of life and is involved in recombination, DNA repair, and protein translation. Multiple evolutionary processes have expanded the set of MutS genes in plants relative to other eukaryotes. Here, we investigate the origins and functions of these plant-specific genes. Land plants, green algae, red algae, and glaucophytes share cyanobacterial-like MutS1 and MutS2 genes that presumably were gained via plastid endosymbiotic gene transfer. MutS1 was subsequently lost in some taxa, including seed plants, whereas MutS2 was duplicated in Viridiplantae (i.e., land plants and green algae) with widespread retention of both resulting paralogs. Viridiplantae also have two anciently duplicated copies of the eukaryotic MSH6 gene (i.e., MSH6 and MSH7) and acquired MSH1 via horizontal gene transfer - potentially from a nucleocytovirus. Despite sharing the same name, "plant MSH1" is not directly related to the gene known as MSH1 in some fungi and animals, which may be an ancestral eukaryotic gene acquired via mitochondrial endosymbiosis and subsequently lost in most eukaryotic lineages. There has been substantial progress in understanding the functions of MSH1 and MSH6/MSH7 in plants, but the roles of the cyanobacterial-like MutS1 and MutS2 genes remain uncharacterized. Known functions of bacterial homologs and predicted protein structures, including fusions to diverse nuclease domains, provide hypotheses about potential molecular mechanisms. Because most plant-specific MutS proteins are targeted to the mitochondria and/or plastids, the expansion of this family appears to have played a large role in shaping plant organelle genetics. One-Sentence SummaryPlants are distinguished from other eukaryotes by a functionally diverse complement of MutS proteins gained via a combination of gene duplication, endosymbiotic gene transfer, and horizontal gene transfer.

evolutionary biology↗