Biology subjects

Swentowsky, K. W.

Publications and source records attributed to Swentowsky, K. W..

4 recordsLinked to original sources

bioRxiv2025

Antagonistic kinesin-14s within a single chromosomal drive haplotype

In maize, there are two meiotic drive systems that operate on large tandem repeat arrays called knobs that are found on chromosome arms. One meiotic drive haplotype, Abnormal chromosome 10 (Ab10), encodes two kinesin proteins that interact with two distinct tandem repeat arrays in a sequence-specific manner to confer meiotic drive. The kinesin KINDR associates with knob180 repeats while the kinesin TRKIN associates with TR-1 repeats. Prior data show that meiotic drive is conferred primarily by the KINDR/knob180 system, with the TRKIN/TR-1 system having little or no role. The second meiotic drive haplotype, K10L2, shows low levels of meiotic drive and only encodes the TRKIN/TR-1 system. Here we used long-read sequencing to assemble the K10L2 haplotype and showed that it has strong homology to an internal portion of the Ab10 haplotype. We also carried out CRISPR mutagenesis of Trkin to test the role of Trkin on Ab10 and K10L2. The data indicate that the Trkin gene on Ab10 does not improve drive or fitness but instead has a weak deleterious effect when paired with a normal chromosome 10. The deleterious effect is more severe when Ab10 is paired with K10L2: in this context functional Trkin on either chromosome nearly abolishes Ab10 drive. We modeled the effect of Trkin on Ab10 and found it should not persist in the population. We conclude that Trkin either confers an advantage to Ab10 in untested circumstances or that it is in the process of being purged from the Ab10 population. ARTICLE SUMMARYMendels first law states that paired chromosomes are transmitted through meiosis at equal frequencies. Some chromosome variants, however, are transmitted at higher frequencies in a process called meiotic drive. We wanted to know the function of a motor protein called TRKIN that is encoded on a maize meiotic drive chromosome. Surprisingly, we found that TRKIN provides no advantage to the meiotic driver and instead seems to be deleterious, suggesting it had a function in a wild ancestor but is now being purged from the population. The results illustrate how genomes are shaped by often-conflicting forces of selection and selfish genetic elements.

evolutionary biology↗

bioRxiv2022

Synthetic maize centromeres transmit chromosomes across generations

Centromeres are long, often repetitive regions of genomes that bind kinetochore proteins and ensure normal chromosome segregation. Engineering centromeres that function in vivo has proven to be difficult. Here we describe a LexA-CENH3 tethering approach that activates functional centromeres at maize synthetic repeat arrays containing LexO binding sites. The synthetic centromeres are sufficient to cause chromosome breakage and release of chromosome fragments that are passed through meiosis and into progeny. Several independent chromosomes were identified, each with newly created centromeres localized over the repeat arrays where they were directed. The new centromeres were self-sustaining and stably transmitted chromosomes to progeny in the absence of the LexA-CENH3 activator. Our results demonstrate the feasibility of using synthetic centromeres for karyotype engineering applications.

genetics↗

bioRxiv2021

The maize gene maternal depression of r1 (mdr1) encodes a DNA glycosylase with maternal and paternal fertility functions

Demethylation of transposons can activate expression of nearby genes and cause imprinted gene expression in endosperm, and it is hypothesized to lead to expression of transposon siRNAs that reinforce silencing in the next generation through transfer either into egg or embryo. Here we describe maternal derepression of r1 (mdr1), which encodes a DNA glycosylase with homology to Arabidopsis DEMETER and which is partially responsible for demethylation of thousands of regions in endosperm. Instead of promoting siRNA expression in endosperm, MDR1 activity inhibits it. Methylation of most repetitive DNA elements in endosperm is not significantly affected by MDR1, with an exception of Helitrons. While maternally-expressed imprinted genes preferentially overlap with MDR1 demethylated regions, the majority of genes that overlap demethylated regions are not imprinted. Double mutant megagametophytes lacking both MDR1 and its close homolog DNG102 result in early seed failure, and double mutant microgametophytes fail pre-fertilization. These data establish DNA demethylation by glycosylases as essential in maize endosperm and pollen and suggest that neither transposon repression nor genomic imprinting are its main function in endosperm.

genetics↗

bioRxiv2020

Gapless assembly of maize chromosomes using long read technologies

Creating gapless telomere-to-telomere assemblies of complex genomes is one of the ultimate challenges in genomics. We used long read technologies and an optical map based approach to produce a maize genome assembly composed of only 63 contigs. The B73-Ab10 genome includes gapless assemblies of chromosome 3 (236 Mb) and chromosome 9 (162 Mb), multiple highly repetitive centromeres and heterochromatic knobs, and 53 Mb of the Ab10 meiotic drive haplotype.

bioinformatics↗